Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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OSCILLATOR GENERATORS AND METHODS OF USING THEM
[0001] PRIORITY APPLICATION
[0002] This application is related to, and claims priority to and the
benefit of, U.S. Application No.
15/140,294 filed on April 27, 2016, the entire disclosure of which is hereby
incorporated herein by
reference for all purposes.
[0003] TECHNOLOGICAL FIELD
[0004] This application is related to generators and methods of using them.
More particularly,
certain embodiments described herein are directed to a generator that is
operative in one or more
oscillations modes to sustain a plasma or other atomization/ionization device.
[0005] BACKGROUND
[0006] Generators are commonly used to sustain a plasma within a torch
body. A plasma includes
charged particles. Plasmas have many uses including atomizing and/or ionizing
chemical species.
[0007] SUMMARY
[0008] Certain aspects, attributes and features are directed to generators
that may be operated in
one or more oscillation modes. The generator may be used to power many
different types of devices
including, but not limited to, induction devices.
[0009] In a first aspect, a generator configured to sustain an inductively
coupled plasma in a torch
body is provided. In certain configurations, the generator comprises a
processor and an oscillation
circuit electrically coupled to the processor, the oscillation circuit
configured to electrically couple to
an induction device and provide power to the induction device in an
oscillation mode to sustain the
inductively coupled plasma in the torch body, the circuit configured to
provide harmonic emission
control during sustaining of the inductively coupled plasma in the torch body
in the oscillation mode of
the generator is provided.
[0010] In certain examples, the circuit comprises a first transistor
configured to electrically couple
to the induction device, in other examples, the circuit further comprises a
first driver electrically
coupled to the first transistor and configured to electrically couple to the
induction device. In some
embodiments, the first driver is configured to electrically couple to the
induction device through a first
low pass filter. In other embodiments, the circuit further comprises a second
driver electrically
coupled to the second transistor and configured to electrically couple to the
induction device. In some
instances, the second driver is configured to electrically couple to the
induction device through a
second low pass filter. In other instances, each of the first low pass filter
and the second low pass filter
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is configured to filter a feedback signal provided to the first power
transistor and the second power
transistor. In further examples, each of the first low pass filter and the
second low pass filter comprise
a high order ceramic low-pass filter. In some embodiments, the high order
ceramic low pass filter is
configured to provide at least a 20 dB cut off at 200 MHz or higher
frequencies. In other examples, the
circuit is configured to provide impedance matching within about three RF
cycles. In some instances,
the generator may comprise a detector electrically coupled to the processor
and configured to
determine when the plasma is ignited. In some examples, the processor is
configured to disable the
oscillation circuit if the plasma is extinguished. In other embodiments, the
generator may comprise a
signal converter between the processor and the detector. In certain instances,
the oscillation circuit is
configured to electrically couple to an induction device that comprises an
induction coil or a plate
electrode. In some examples, the oscillation circuit is configured to divide
power evenly to the first
transistor and the second transistor. In other examples, the oscillation
circuit is configured to cross
couple feedback signals from the induction device to the first transistor and
the second transistor to
divide the power evenly. In certain embodiments, the oscillation circuit
comprises a first feedback
resistor electrically coupled to the first transistor. In some examples, the
oscillation circuit comprises a
second feedback resistor electrically coupled to the second transistor. In
certain configurations, the
oscillation circuit comprises a first DC block capacitor electrically coupled
to the first transistor. In
other configurations, the oscillation circuit comprises a second DC block
capacitor electrically coupled
to the second transistor. In some examples, the generator comprises a circuit
as shown in FIG. 37,
FIG. 38 or FIG. 40.
[0011] In another aspect, an oscillation generator configured to provide
power to an induction
device surrounding at least some portion of a torch body is described. For
example, the oscillation
generator can be configured to provide power to the induction device to ignite
an inductively coupled
plasma in the torch body in a first state of the oscillation generator and to
provide power to the
induction device to sustain the inductively coupled plasma in the torch body
in a second state of the
oscillation generator, in which the oscillation generator comprises: an
oscillation circuit configured to
provide a first frequency to the induction device in the first state of the
generator. In certain
configurations, the oscillation circuit is configured to provide a second
frequency to the induction
device in the second state, wherein the second frequency is higher than the
first frequency, and a
processor configured to switch the generator from the first state to the
second state after ignition of the
inductively coupled plasma.
[0012] In some embodiments, the oscillator circuit is configured to provide
harmonic emission
control. In other embodiments, the circuit comprises a first transistor
configured to electrically couple
to an induction device. In additional examples, the circuit further comprises
a first driver electrically
coupled to the first transistor and configured to electrically couple to the
induction device. In further
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examples, the first driver is configured to electrically couple to the
induction device through a first low
pass filter. In some embodiments, the circuit further comprises a second
driver electrically coupled to
the second transistor and configured to electrically couple to the induction
device. In other examples,
the second driver is configured to electrically couple to the induction device
through a second low pass
filter. In certain instances, each of the first low pass filter and the second
low pass filter is configured
to filter a feedback signal provided to the first power transistor and the
second power transistor. In
some examples, each of the first low pass filter and the second low pass
filter comprises a high order
ceramic low-pass filter. In other examples, the high order ceramic low pass
filter is configured to
provide a 20 dB cut off at 200 MHz or higher frequencies. In certain
embodiments, the circuit is
configured to provide impedance matching within about three RF cycles after
the generator is switched
from the first state to the second state. In other embodiments, the generator
may comprise a detector
electrically coupled to the processor and configured to determine when the
plasma is ignited. In some
instances, the processor is configured to disable the oscillation circuit if
the plasma is extinguished. In
certain examples, the generator comprises a signal converter between the
processor and the detector.
In some embodiments, the oscillation circuit is configured to electrically
couple to an induction device
that comprises an induction coil or a plate electrode. In other embodiments,
the oscillation circuit is
configured to divide power evenly to the first transistor and the second
transistor. In further examples,
the oscillation circuit is configured to cross couple feedback signals from
the induction device to the
first transistor and the second transistor to divide the power evenly. In some
examples, the oscillation
circuit comprises a first feedback resistor electrically coupled to the first
transistor and a second
feedback resistor electrically coupled to the second transistor. In other
configurations, the oscillation
circuit comprises a first DC block capacitor electrically coupled to the first
transistor. In some
examples, the oscillation circuit comprises a second DC block capacitor
electrically coupled to the
second transistor. In some examples, the generator comprises a circuit as
shown in FIG. 37, FIG. 38 or
FIG. 40.
[0013] In an additional aspect, a radio frequency generator configured to
power an induction
device is disclosed. In some configurations, the generator comprises a circuit
configured to provide
power to the induction device in a first oscillation mode and to provide power
to the induction device
in a second oscillation mode.
[0014] In some instances, the circuit comprises a first transistor
configured to electrically couple to
the induction device to provide power to the induction device. In other
instances, the circuit further
comprises a first driver electrically coupled to the first transistor and
configured to electrically couple
to the induction device. In some configurations, the first driver is
configured to electrically couple to
the induction device through a first low pass filter. In other configurations,
the circuit further
comprises a second driver electrically coupled to the second transistor and
configured to electrically
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couple to the induction device. In some examples, the second driver is
configured to electrically
couple to the induction device through a second low pass filter. In certain
examples, each of the first
low pass filter and the second low pass filter is configured to filter a
feedback signal provided to the
first power transistor and the second power transistor. In some embodiments,
each of the first low pass
filter and the second low pass filter comprise a high order ceramic low-pass
filter. In certain examples,
the high order ceramic low pass filter is configured to provide at least a 20
dB cut off at 200 MHz or
higher frequencies. In some examples, the circuit is configured to provide
impedance matching within
about three RF cycles after the generator is switched from the first state to
the second state. In some
examples, the generator comprises a detector electrically coupled to a
processor configured to
determine when the plasma is ignited. In certain embodiments, the processor is
configured to disable
the oscillation circuit if the plasma is extinguished. In other embodiments,
the generator comprises a
signal converter between the processor and the detector. In certain examples,
the oscillation circuit is
configured to electrically couple to an induction device that comprises an
induction coil or a plate
electrode. In certain embodiments, the oscillation circuit is configured to
divide power evenly to the
first transistor and the second transistor. In some examples, the oscillation
circuit is configured to
cross couple feedback signals from the induction device to the first
transistor and the second transistor
to divide the power evenly. In other examples, the oscillation circuit
comprises a first feedback resistor
electrically coupled to the first transistor. In some embodiments, the
oscillation circuit comprises a
second feedback resistor electrically coupled to the second transistor. In
other embodiments, the
oscillation circuit comprises a first DC block capacitor electrically coupled
to the first transistor. In
additional embodiments, the oscillation circuit comprises a second DC block
capacitor electrically
coupled to the second transistor. In sonic examples, the generator comprises a
circuit as shown in FIG.
37, FIG. 38 or FIG. 40.
[0015] In another aspect, a system comprising an induction device, and a
generator electrically
coupled to the induction device and configured to sustain an inductively
coupled plasma in a torch
body, the generator comprising a processor and an oscillation circuit
electrically coupled to the
processor, the oscillation circuit configured to provide power to the
induction device in an oscillation
mode to sustain the inductively coupled plasma in the torch body, wherein the
circuit is further
configured to provide harmonic emission control during sustaining of the
inductively coupled plasma
in the torch body in the oscillation mode of the generator is provided.
[0016] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
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second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0017] In another aspect, a system comprising an induction device, and an
oscillation generator
electrically coupled to the induction device and configured to provide power
to an induction device
surrounding at least some portion of a torch body, the oscillation generator
configured to provide
power to the induction device to ignite an inductively coupled plasma in the
torch body in a first state
of the oscillation generator and to provide power to the induction device to
sustain the inductively
coupled plasma in the torch body in a second state of the oscillation
generator, in which the oscillation
generator comprises an oscillation circuit configured to provide a first
frequency to the induction
device in the first state of the generator, in which the oscillation circuit
is configured to provide a
second frequency to the induction device in the second state, wherein the
second frequency is higher
than the first frequency, and a processor configured to switch the generator
from the first state to the
second state after ignition of the inductively coupled plasma is disclosed.
l00181 In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
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further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. hi other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0019] In another aspect, a system comprisingan induction device, and a
radio frequency generator
electrically coupled to the induction device and configured to provide power
to the induction device,
the generator comprising a circuit configured to provide power to the
induction device in a first
oscillation mode and to provide power to the induction device in a second
oscillation mode is
described.
[0020] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
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embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0021] In another aspect, a mass spectrometer system comprising a torch
configured to sustain an
ionization source, an induction device comprising an aperture for receiving a
portion of the torch and
configure to provide radio frequency energy into the received torch portion, a
generator electrically
coupled to the induction device and configured to sustain an inductively
coupled plasma in the torch,
the generator comprising a processor and an oscillation circuit electrically
coupled to the processor, the
oscillation circuit configured to provide power to the induction device in an
oscillation mode to sustain
the inductively coupled plasma in the torch, wherein the circuit is further
configured to provide
harmonic emission control during sustaining of the inductively coupled plasma
in the torch in the
oscillation mode of the generator, and a mass analyzer fluidically coupled to
the torch is described.
[0022] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
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embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0023] In an additional aspect, a mass spectrometer system comprising a
torch configured to
sustain an ionization source, an induction device comprising an aperture for
receiving a portion of the
torch and configure to provide radio frequency energy into the received torch
portion, an oscillation
generator electrically coupled to the induction device and configured to
provide power to the induction
device, the oscillation generator configured to provide power to the induction
device to ignite an
inductively coupled plasma in the torch in a first state of the oscillation
generator and to provide power
to the induction device to sustain the inductively coupled plasma in the torch
in a second state of the
oscillation generator, in which the oscillation generator comprises an
oscillation circuit configured to
provide a first frequency to the induction device in the first state of the
generator, in which the
oscillation circuit is configured to provide a second frequency to the
induction device in the second
state, wherein the second frequency is higher than the first frequency, and a
processor configured to
switch the generator from the first state to the second state after ignition
of the inductively coupled
plasma, and a mass analyzer fluidically coupled to the torch is provided.
[0024:1 In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
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further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. hi certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0025] In another aspect, a mass spectrometer system comprising a torch
configured to sustain an
ionization source, an induction device comprising an aperture for receiving a
portion of the torch and
configure to provide radio frequency energy into the torch, a radio frequency
generator electrically
coupled to the induction device and configured to provide power to the
induction device, the generator
comprising a circuit configured to provide power to the induction device in a
first oscillation mode and
to provide power to the induction device in a second oscillation mode and a
mass analyzer fluidically
coupled to the torch is described.
[0026] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
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second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0027] In an additional aspect, a system for detecting optical emission
comprising a torch
configured to sustain an ionization source, an induction device comprising an
aperture for receiving a
portion of the torch and configure to provide radio frequency energy into the
torch, a generator
electrically coupled to the induction device and configured to sustain an
inductively coupled plasma in
the torch, the generator comprising a processor and an oscillation circuit
electrically coupled to the
processor, the oscillation circuit configured to provide power to the
induction device in an oscillation
mode to sustain the inductively coupled plasma in the torch, wherein the
circuit is further configured to
provide harmonic emission control during sustaining of the inductively coupled
plasma in the torch in
the oscillation mode of the generator, and an optical detector configured to
detect optical emissions in
the torch.
[0028] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
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filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0029] In another aspect, a system for detecting optical emission
comprising a torch configured to
sustain an ionization source, an induction device comprising an aperture for
receiving a portion of the
torch and configure to provide radio frequency energy into the torch, an
oscillation generator
electrically coupled to the induction device and configured to provide power
to the induction device,
the oscillation generator configured to provide power to the induction device
to ignite an inductively
coupled plasma in the torch in a first state of the oscillation generator and
to provide power to the
induction device to sustain the inductively coupled plasma in the torch in a
second state of the
oscillation generator, in which the oscillation generator comprises an
oscillation circuit configured to
provide a first frequency to the induction device in the first state of the
generator, in which the
oscillation circuit is configured to provide a second frequency to the
induction device in the second
state, wherein the second frequency is higher than the first frequency, and a
processor configured to
switch the generator from the first state to the second state after ignition
of the inductively coupled
plasma, and an optical detector configured to detect optical emissions in the
torch.
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[0030] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0031] In another aspect, a system for detecting optical emission
comprising a torch configured to
sustain an ionization source, an induction device comprising an aperture for
receiving a portion of the
torch and configured to provide radio frequency energy into the torch, a radio
frequency generator
electrically coupled to the induction device and configured to provide power
to the induction device,
the generator comprising a circuit configured to provide power to the
induction device in a first
oscillation mode and to provide power to the induction device in a second
oscillation mode, and an
optical detector configured to detect optical emissions in the torch is
described.
[0032] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
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driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0033] In an additional aspect, a system for detecting atomic absorption
emission, the system
comprising a torch configured to sustain an ionization source, an induction
device comprising an
aperture for receiving a portion of the torch and configured to provide radio
frequency energy into the
torch, a generator electrically coupled to the induction device and configured
to sustain an inductively
coupled plasma in the torch, the generator comprising a processor and an
oscillation circuit electrically
coupled to the processor, the oscillation circuit configured to provide power
to the induction device in
an oscillation mode to sustain the inductively coupled plasma in the torch,
wherein the circuit is further
configured to provide harmonic emission control during sustaining of the
inductively coupled plasma
in the torch in the oscillation mode of the generator, a light source
configured to provide light to the
torch, and an optical detector configured to measure the amount of provided
light transmitted through
the torch is disclosed.
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[0034] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0035] In another aspect, a system for detecting atomic absorption emission
comprising a torch
configured to sustain an ionization source, an induction device comprising an
aperture for receiving a
portion of the torch and configured to provide radio frequency energy into the
torch, an oscillation
generator electrically coupled to the induction device and configured to
provide power to the induction
device, the oscillation generator configured to provide power to the induction
device to ignite an
inductively coupled plasma in the torch in a first state of the oscillation
generator and to provide power
to the induction device to sustain the inductively coupled plasma in the torch
in a second state of the
oscillation generator, in which the oscillation generator comprises an
oscillation circuit configured to
provide a first frequency to the induction device in the first state of the
generator, in which the
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oscillation circuit is configured to provide a second frequency to the
induction device in the second
state, wherein the second frequency is higher than the first frequency, and a
processor configured to
switch the generator from the first state to the second state after ignition
of the inductively coupled
plasma, a light source configured to provide light to the torch, and an
optical detector configured to
measure the amount of provided light transmitted through the torch is
disclosed.
[0036] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0037] In another aspect, a system for detecting atomic absorption
emission, the system
comprising a torch configured to sustain an ionization source, an induction
device comprising an
aperture for receiving a portion of the torch and configure to provide radio
frequency energy into the
torch, a radio frequency generator electrically coupled to the induction
device and configured to
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provide power to the induction device, the generator comprising a circuit
configured to provide power
to the induction device in a first oscillation mode and to provide power to
the induction device in a
second oscillation mode, a light source configured to provide light to the
torch, and an optical detector
configured to measure the amount of provided light transmitted through the
torch is described.
[0038] In certain examples, the circuit comprises a first transistor and a
second transistor each
electrically coupled to the induction device. In other examples, the circuit
further comprises a first
driver electrically coupled to the first transistor and electrically coupled
to the induction device. In
further examples, the first driver is electrically coupled to the induction
device through a first low pass
filter. In some examples, the circuit further comprises a second driver
electrically coupled to the
second transistor and electrically coupled to the induction device. In other
embodiments, the second
driver is electrically coupled to the induction device through a second low
pass filter. In some
embodiments, each of the first low pass filter and the second low pass filter
is configured to filter a
feedback signal provided to the first power transistor and the second power
transistor. In additional
embodiments, each of the first low pass filter and the second low pass filter
comprise a high order
ceramic low-pass filter. In some configurations, the high order ceramic low
pass filter is configured to
provide at least a 20 dB cut off at 200 MHz or higher frequencies. In certain
instances, circuit is
configured to provide impedance matching within about three RF cycles. In
other instances, the
system comprises a detector electrically coupled to the processor and
configured to determine when the
plasma is ignited. In further examples, the processor is configured to disable
the oscillation circuit if
the plasma is extinguished. In additional examples, the system comprises a
signal converter between
the processor and the detector. In some embodiments, the induction device
comprises an induction coil
or a plate electrode. In other embodiments, the oscillation circuit is
configured to divide power evenly
to the first transistor and the second transistor. In some configurations, the
oscillation circuit is
configured to cross couple feedback signals from the induction device to the
first transistor and the
second transistor to divide the power evenly. In other configurations, the
oscillation circuit comprises
a first feedback resistor electrically coupled to the first transistor. In
additional configurations, the
oscillation circuit comprises a second feedback resistor electrically coupled
to the second transistor. In
some embodiments, the oscillation circuit comprises a first DC block capacitor
electrically coupled to
the first transistor. In certain embodiments, the oscillation circuit
comprises a second DC block
capacitor electrically coupled to the second transistor.
[0039] In another aspect, a chemical reactor comprising a reaction chamber,
an induction device
comprising an aperture configured to receive some portion of the reaction
chamber, and any generator
as described herein electrically coupled to the induction device and
configured to provide power into
the received portion of the reaction chamber using the induction device is
disclosed.
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[0040] In an additional aspect, a material deposition device comprising an
atomization chamber,
an induction device comprising an aperture configured to receive some portion
of the atomization
chamber, any generator ad described herein electrically coupled to the
induction device and configured
to provide power into the received portion of the atomization chamber using
the induction device, and
a nozzle fluidically coupled to the atomization chamber and configured to
receive atomized species
from the chamber and provide the received, atomized species towards a
substrate is disclosed.
[0041] In another aspect, a system comprises a torch, a first induction
device comprising an
aperture configured to receive a portion of the torch, a second induction
device comprising an aperture
configured to receive a second portion of the torch, a first generator
electrically coupled to the first
induction device and a second generator electrically coupled to the second
induction device, in which
at least one of the first generator and the second generator is any one of the
generators described
herein. In some instances, each of the first generator and the second
generator is any one of the
generators described herein.
[0042] In an additional aspect, a method of igniting and sustaining a
plasma with a single
generator comprising igniting a plasma in a torch body by providing power to
an induction device from
the generator in a first oscillation mode, and switching the generator from
the first oscillation mode to a
second oscillation mode any time after the plasma is ignited is provided. The
method may use a
generator comprising the circuit of FIG. 37 or FIG. 38 or FIG. 40.
[0043] In another aspect, a method of igniting and sustaining a plasma with
a single generator
comprising igniting a plasma in a torch body by providing power to an
induction device from a
generator configured to provide power to the induction device in a first
oscillation mode and in an
second oscillation mode, and sustaining the plasma using the second
oscillation mode of the generator.
In some instances, the plasma is ignited by providing power from the generator
in the first oscillation
mode. In other instances, the method comprises switching the generator to the
first oscillation mode
after the plasma is sustained for some period using the second oscillation
mode.
[0044] In an additional aspect, a method of sustaining an inductively
coupled plasma, the method
comprising providing power to a torch in an oscillation mode using a generator
circuit as shown in one
of FIGS. 37, 38 and 40.
[0045] In another aspect, a generator configured to sustain an inductively
coupled plasma in a
torch body comprising a processor and an oscillation circuit electrically
coupled to the processor, the
oscillation circuit configured to electrically couple to an induction device
and provide power to the
induction device in an oscillation mode to sustain the inductively coupled
plasma in the torch body, the
oscillation circuit configured to provide independent control of voltage and
current provided to a
transistor of the oscillation circuit is provided.
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[0046] In an additional aspect, an oscillation generator configured to
provide power to an
induction device surrounding at least some portion of a torch body, the
oscillation generator configured
to provide power to the induction device to ignite an inductively coupled
plasma in the torch body in a
first state of the oscillation generator and to provide power to the induction
device to sustain the
inductively coupled plasma in the torch body in a second state of the
oscillation generator, in which the
oscillation generator comprises an oscillation circuit configured to provide a
first frequency to the
induction device in the first state of the generator, in which the oscillation
circuit is configured to
provide a second frequency to the induction device in the second state,
wherein the second frequency is
higher than the first frequency, the oscillation circuit further configured to
provide independent control
of voltage and current provided to a transistor of the oscillation circuit,
and a processor configured to
switch the generator from the first state to the second state after ignition
of the inductively coupled
plasma is disclosed.
[0047] In another aspect, a radio frequency generator configured to power
an induction device
comprises a circuit configured to provide power to the induction device in a
first oscillation mode and
to provide power to the induction device in a second oscillation mode, wherein
the circuit is further
configured to provide independent control of voltage and current provided to a
transistor of the
oscillation circuit that provides power to the induction device.
[0048] In an additional aspect, a generator configured to sustain an
inductively coupled plasma in
a torch body comprises a processor and a circuit electrically coupled to the
processor, the circuit
configured to electrically couple to an induction device and provide power to
the induction device in an
oscillation mode to sustain the inductively coupled plasma in the torch body,
wherein the circuit does
not include a driven mode circuit.
[0049] In another aspect, an oscillation generator configured to provide
power to an induction
device surrounding at least some portion of a torch body is configured to
provide power to the
induction device to ignite an inductively coupled plasma in the torch body in
a first state of the
oscillation generator and to provide power to the induction device to sustain
the inductively coupled
plasma in the torch body in a second state of the oscillation generator, in
which the oscillation
generator comprises an oscillation circuit configured to provide a first
frequency to the induction
device in the first state of the generator, in which the oscillation circuit
is configured to provide a
second frequency to the induction device in the second state, wherein the
second frequency is higher
than the first frequency, in which the oscillation generator does not include
a driven mode circuit, and a
processor configured to switch the generator from the first state to the
second state after ignition of the
inductively coupled plasma.
[0050] In another aspect, a radio frequency generator configured to power
an induction device
comprises a circuit configured to provide power to the induction device in a
first oscillation mode and
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to provide power to the induction device in a second oscillation mode, wherein
the circuit does not
include a driven mode circuit.
[0051] Additional features, aspects, examples, configurations and
embodiments are described in
more detail below.
[0052] BRIEF DESCRIPTION OF THE DRAWINGS
[0053] Certain embodiments of the devices and systems are described with
reference to the
accompanying figures in which:
[0054] FIG. 1 is a block diagram of a generator, in accordance with certain
examples;
[0055] FIG. 2A is a circuit suitable for powering an induction device in a
driven mode, in
accordance with certain examples;
[0056] FIG. 2B is a circuit suitable for powering an induction device in an
oscillation mode, in
accordance with certain examples;
[0057] FIG. 2C is another circuit suitable for powering an induction device
in a hybrid mode, in
accordance with certain examples;
[0058] FIGS 3A and 3B are illustrations of alternative configurations for
use in the circuit of
FIGS. 2A-2C, in accordance with certain configurations;
[00591 FIGS. 4A and 4B are additional illustrations of alternative
configurations for use in the
circuit of FIGS. 2A-2C, in accordance with certain configurations;
[00601 FIG. 5 is a schematic of an illustrative generator circuit suitable
for use in powering an
induction device in a driven mode, an oscillation mode and a hybrid mode, in
accordance with certain
configurations;
[0061] FIG. 6A is an illustration of a torch and load coil device that can
be used to sustain an
inductively coupled plasma, in accordance with certain examples;
[0062] FIG. 6B is an illustration of a torch and plate electrodes that can
be used to sustain an
inductively coupled plasma, in accordance with certain examples;
[0063] FIGS. 7, 8 and 9 are block diagrams of two load coils separately
powered by two
generators, in accordance with certain examples;
[0064] FIGS. 10, 11 and 12 are block diagrams of two plate electrodes
separately powered by two
generators, in accordance with certain examples;
[00651 FIGS. 13, 14, 15, 16, 17 and 18 are block diagrams of a load coil
and a set of plate
electrodes separately powered by two generators, in accordance with certain
examples;
[0066] FIGS. 19, 20, 21 and 22 are block diagrams of two induction devices
powered by a single
generator, in accordance with certain examples;
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[0067] FIG. 23 is a block diagram of an optical emission system, in
accordance with certain
examples;
[0068] FIG. 24 is a block diagram of an atomic absorption system, in
accordance with certain
examples;
[0069] FIG. 25 is a block diagram of another atomic absorption system, in
accordance with certain
examples;
[0070] FIG. 26 is a block diagram of a mass spectrometer, in accordance
with certain examples;
[0071] FIG. 27 is a circuit of a generator suitable for operation in a
driven mode and in an
oscillation mode and being operated in the driven mode, in accordance with
certain examples;
[0072] FIG. 28 is the circuit of FIG. 27 being operated in the oscillation
mode, in accordance with
certain examples;
[0073] FIG. 29 shows a spectrum for lithium and beryllium obtained using
the generator and the
mass spectrometer, in accordance with certain examples;
[0074] FIG. 30 shows a spectrum for magnesium obtained using the generator
and the mass
spectrometer, in accordance with certain examples;
[0075] FIG. 31 shows a spectrum for indium obtained using the generator and
the mass
spectrometer, in accordance with certain examples;
[0076] FIG. 32 shows a spectrum for uranium-238 obtained using the
generator and the mass
spectrometer, in accordance with certain examples;
[0077] FIG. 33 is a table comparing the results obtained using the hybrid
generator (driven mode
and oscillation mode) and a standard NexION instrument, in accordance with
certain examples;
[0078] FIG. 34 is a graph of intensity versus time for indium, cerium,
cerium oxide and uranium as
the differential phase is imbalanced, in accordance with certain examples;
[0079] FIG. 35 is a table showing the measurement of several elements using
a standard NexION
instrument and a hybrid generator in both a driven mode and in an oscillation
mode, in accordance with
certain examples;
[0080] FIG. 36 is an illustration showing an oscillation circuit, in
accordance with certain
examples;
[0081] FIG. 37 is an illustration showing low-pass filters that can be
used, for example, to filter the
feedback signal to suppress high harmonics, in accordance with certain
configurations;
[0082] FIG. 38 is an illustration showing a suitable circuit for harmonic
emission control, in
accordance with certain embodiments;
[0083] FIG. 39 is a graph showing the output capacitance of a typical
device suitable for use as a
driver, in accordance with certain embodiments;
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[0084] FIG. 40 is an illustrative circuit configuration for balancing the
input power to the power
devices, in accordance with certain examples; and
[0085] FIG. 41 is a graph showing the emission of a 34 MHz plasma generator
at the harmonics
(multiples of 34 MHz), in accordance with certain configurations.
[0086] It will be recognized by the person of ordinary skill in the art,
given the benefit of this
disclosure, that certain dimensions or features of the components of the
systems may have been
enlarged, distorted or shown in an otherwise unconventional or non-
proportional manner to provide a
more user friendly version of the figures. In addition, the exact length,
width, geometry, aperture size,
etc. of the torch body, the plasmas generated and other components herein may
vary.
[0087] DETAILED DESCRIPTION
[0088] Certain embodiments are described below with reference to singular
and plural terms in
order to provide a user friendly description of the technology disclosed
herein. These terms are used
for convenience purposes only and are not intended to limit the devices,
methods and systems
described herein. Certain examples are described herein with reference to the
terms driven mode and
oscillation mode. While the exact parameters used in the driven mode and in
the oscillation mode
may vary, the RF generator frequency for plasma generation is usually from
10MHz to 90MHz, more
particularly between 20MHz and 50MHz, for example about 40MHz. The RF
generator output power
is typically about 500 Watts to 50kW. As described in more detail herein, in
the driven mode of
operation, the feedback loop can be disabled and the voltage can be selected
to provide a desired power
to the induction device. In the oscillation mode, the feedback loop can be
enabled to permit rapid
changing of the impedance. If desired, the generator can operate entirely in
the driven mode, which
can achieve a higher sensitivity for mass spectrometry in certain
applications, compared to the
oscillation mode. In some embodiments, the driven + oscillator hybrid
generator may be part of ICP-
OES or ICP-MS or other similar instruments as described herein. In certain
embodiments, generator
operation can be controlled with a processor or master controller in or
electrically coupled to the
generator to control the generator, e.g., to enable or terminate the plasma
generation. While two modes
are possible with the generators described herein, if desired, the generator
can be operated in only a
single mode, e.g., in only the drive mode or in only the oscillation mode.
[0089] Certain embodiments are also described below that use a generator to
generate and/or
sustain an inductively coupled plasma. If desired, however, the same generator
can be used to generate
and/or sustain a capacitively coupled plasma, a flame or other
atomization/ionization devices that can
be used, for example, to atomize and/or ionize chemical species. Certain
configurations are provided
below using inductively coupled plasmas to illustrate various aspects and
attributes of the technology
described herein.
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[0090] In certain examples, the generators described herein can be used to
sustain a high-energy
plasma to atomize and/or ionize samples for chemical analysis, to provide ions
for deposition or other
uses. To ignite and sustain the plasma, RF power, typically in the range of
0.5 kW to 100kW, from a
RF generator (RFG) is inductively coupled to the plasma by a load coil, plate
electrode or other
suitable induction devices. The plasma exhibits different RF impedance during
the ignition phase and
when the plasma is subject to different chemical samples. To facilitate
optimal power transfer, the RF
generator can be configured to adapt the impedance matching to the varying
plasma impedance.
[0091] In certain embodiments, existing RF generators are configured to
operate using only one of
the two methods: the oscillator method (or mode) or the driven method (or
mode). Each of these
methods has advantages and weaknesses. In the oscillation method, the RF
generator is a power
oscillator circuit. The oscillation frequency is determined by the
oscillator's resonant circuit. In many
instances, the plasma impedance and the induction device are part of the
resonator and feedback path,
so that the oscillating frequency can be rapidly changed to adapt to the
varying plasma impedance.
This attribute facilitates the analysis of different unknown samples at a high
throughput rate. When the
oscillation method is implemented during plasma ignition, the RF impedance of
the induction device
can change substantially and abruptly from no plasma to successful plasma
generation. Prior to
ignition, the induction device behaves like an inductor such that all the RF
power provided to the
inductor is substantially reactive power (i.e., no real power). After
successful plasma ignition, the
inductive device inductively couples real power to the plasma. The feedback
signals of the oscillator,
which are derived from the induction device, to drive the power transistors
change abruptly as well.
As a result, during plasma ignition the feedback signals are poorly
controlled, and there is a substantial
risk in damaging the power electronics when the oscillation method is
implemented for plasma
ignition. The breakdown of silicon power transistors, which are most commonly
used for RF power
generation at the aforementioned frequency range, is about -6V to +12V at the
gate (input), and about
+150V for drain breakdown. Older but slower silicon transistors may have gate
breakdown limits from
-40V to +40V. Damage prevention of the electronics is particularly desirable
because advancements in
semiconductor technologies is often achieved by device scaling (e.g., to a
smaller gate length), such
that the transistor speed (e.g., unity gain frequency Ft, or the maximum
oscillation frequency Fmax) is
increased at the expense of a lower device breakdown voltage limit. The
increase in the transistor
speed facilitates the design of a high efficiency power amplifier (e.g., class
C, class D, class E, class F,
etc.), because the available power gain at the higher harmonics above the
fundamental frequency can
used to optimize the signal waveform and current conduction angle.
Implementation of these high
speed, lower breakdown devices can be weighed against the not well controlled
feedback signal during
ignition. A rapid increase in the feedback signal amplitude can rapidly
reinforce an uncontrolled
positive feedback loop such that the transistors of the generator are
destroyed. The excessive signals
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can be difficult to suppress or control because of the high frequency, high
power and the inherent
instability in an oscillator for plasma ignition. If the feedback signal is
suppressed too much to
safeguard the transistor, the plasma may fail to ignite. Furthermore, the
oscillator design can manifest
higher RF spurious signals and higher phase noise. Such imperfections may
compromise the
equipment sensitivity. To overcome these issues, a generator configured to
implement only the
oscillation method would typically include higher breakdown transistors that
are more expensive
and/or lower speed and efficiency to avoid potential damage to the circuitry
components.
[0092] Generators configured to implement only the driven method (or mode)
typically utilize a
stable RF source which operates at a controlled frequency and amplitude, e.g.,
a frequency that is
adjustable or fixed (but can vary) and is predetermined or preselected.
Typical examples of signal
sources are small signal, e.g., less than 10 Watt, RF synthesizers or voltage-
controlled oscillators
(VCO) comprising high-quality crystal, RLC or RC resonators. A RF power
amplifier magnifies the
small controlled RF signal to a high power level for plasma generation. The
driven method is
advantageous for plasma ignition because the controlled frequency and signal
amplitude can be
selected to avoid transistor breakdown. In addition, in many instances, the
driven method can produce
a spectrally purer RF signal, e.g., a signal spectrum with a strong signal
tone at the intended signal
frequency and less RF spurious signals. In some configurations, it is easier
to use a driven mode RF
generator to achieve higher sensitivity for mass spectrometry, compared to an
oscillation mode RF
generator. However, impedance matching in generators configured to implement
the driven method is
often much slower than those implementing the oscillation method. A driven RF
generator adjusts the
controlled frequency (or phase) and/or the amplitude by monitoring the RF
impedance change, so that
a feedback (or error) signal can be generated to adjust the frequency or phase
of the RF source,
typically by means of a phase-locked loop (PLL). In the oscillator method, the
change is often within a
couple of RF cycles, whereas the change in the driven method is at a rate of
tens to thousands of RF
cycles or at least 10-1000X slower than the oscillation method. As a result,
it is more difficult to
design a driven RF generator for high throughput mass spectrometry analysis.
RF power amplifiers
used in the driven method are often designed to drive standard 50 Ohm or 75
Ohm loads. Additional
impedance matching between a 50 Ohm (or 75 Ohm) load to the transistors
further complicates the
design, increases components and footprint area, and can cause unwanted power
loss.
[0093] In certain configurations of the generators described herein, the
generators may include
suitable components to permit operation in the driven mode and in the
oscillation mode. The generator
may switch (if desired) between the two modes during different periods of
operation of the plasma to
provide optimum power to the plasma at different periods. For example, during
ignition of the plasma,
the generator may be operated in the driven mode to provide better control of
the frequency and signal
amplitude to avoid transistor breakdown. After ignition of the plasma, the
generator can remain in the
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driven mode, if desired, or may be switched to the oscillation mode to permit
more rapid impedance
matching with changes in the plasma that may occur during introduction of
samples. The ability to
implement both the driven mode and the oscillation mode using a single
generator permits the use of
lower breakdown transistors that are more inexpensive and/or provide higher
speeds and efficiency.
While various embodiments are described herein as using the hybrid generator
in the driven mode to
ignite the plasma, if desired, the generator may be operated in the
oscillation mode during plasma
ignition and/or after plasma ignition.
[0094] In certain examples, the generators described herein may include
suitable components and
circuitry to permit operation in both the driven mode and the oscillation mode
and to permit rapid
switching between the two modes. For example, the generator may comprise power
transistors, driver
amplifiers, various switches, e.g., an RF switch, and an impedance matching
network. Feedback
signals derived from the induction device outputs can be used to drive the
power transistors by a switch
(or a variable-gain circuit). The feedback signals can be enabled, disabled or
adjusted in amplitude by
the switch, typically implemented with an adjustable gain circuit element
(e.g., single-stage transistor,
multi-stage amplifier, variable gain amplitude, variable digital or analog
attenuator, variable capacitor
or other adjustable coupling devices, etc.). The saturated output power of the
switch or "switching"
circuit can be selected to limit or control the physical power of the feedback
signal. For example, if a
single-stage transistor is used as a switch, the power supply, e.g., a VDD
power supply, can be reduced
such that the saturated (maximum) output power of the switch is always lower
than the maximum input
power allowed by the power transistors. In this configuration, the transistors
are protected in the
oscillation mode of operation. In addition, a RF driver amplifier can be used
to amplify the RF source
to drive the power transistors. When these components are implemented
together, the RF generator
can be operated in the driven mode, an oscillation mode and an injection-
locked mode, which is a
hybrid mode with characteristics of both the driven mode and the oscillation
mode and is present
during the transition from the driven mode to the oscillation mode or vice
versa. In certain
embodiments when the driven mode is implemented, the feedback signals are
disabled by the switches
and the RF driver amplifier is enabled. To switch from the driven mode to the
oscillation mode, the
feedback signal switches are enabled and the RF driver amplifier is disabled.
The RF generator can
also be in the injection-locked mode, for example, when both the feedback
signals and the RF driver
amplifiers are enabled. In this case, the RF generator is running in the
oscillation mode, but its
operating frequency is locked to the RF source frequency of the driven mode.
The ability to switch
between the various modes using a single generator provides desirable
attributes including, but not
limited to, minimizing transistor breakdown in the driven mode during
ignition, being able to rapidly
change the impedance in the oscillation mode during sample introduction and/or
analysis, and the
ability to use cheaper and faster transistors while reducing the likelihood of
transistor failure. If
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desired, the generator may be rapidly switched between the driven mode and the
oscillation mode and
back to the driven mode to sustain a plasma using an almost continuous
injection-locked mode.
[0095] In certain examples and referring to FIG. 1, a simplified block
diagram of a generator is
shown. The generator 100 comprises a driving circuit 110 that is configured to
be enabled during
operation of the generator 100 in the driven mode. The driving circuit 110 is
shown as being
electrically coupled to a load coil 130, though as described herein, the load
coil 130 may be replaced
with other induction devices including plate electrodes, for example. The
generator 100 also comprises
an oscillating circuit 120 electrically coupled to the load coil 130. Each of
the circuits 110, 120 are
electrically coupled to a power source (not shown). The driving circuit 110
and the oscillating circuit
120 may each be electrically coupled to a controller or processor 140 to
permit operation of the
different circuits 110, 120 at selected periods. In one method of operating
the generator 100, a plasma
is ignited by introducing a gas into the torch body 135, which is surrounded
by the load coil 130. The
plasma can be ignited with a spark or arc and sustained by enabling the
driving circuit 110 to provide a
controlled, driven RF signal to the plasma in the driven mode. When the plasma
impedance stabilizes
(or after a desired or selected time), the generator may be switched over from
the driven mode to the
oscillation mode. During the switch over process, both the driving circuit 110
and the oscillating
circuit 120 may be enabled for some period, which provides an injection-locked
mode. The driving
circuit 110 can be disabled while keeping the oscillating circuit 120 enabled
to switch the generator
100 over to the oscillation mode. Sample may then be introduced into the
plasma, and the oscillation
mode permits rapid adjustment of the impedance as the plasma becomes loaded
with sample/solvent.
If desired, and for certain samples, the generator 100 may be switched back to
the driven mode for
analysis. As described herein, for certain analyses, the driven mode may
provide higher sensitivities
compared to the oscillation mode. While the circuits 110, 120 are shown as
separate circuits in FIG. 1
for illustration, the components of the driving circuit 110 and oscillating
circuit 120 may be combined
together as noted in more detail below.
[0096] In certain embodiments and referring to FIG. 2A, a schematic of
certain active components
of a circuit suitable for implementing the driven mode and the oscillation
mode is shown. In the
schematic shown in FIG. 2A various components are active to permit operation
of the circuit in the
driven mode. The circuit 200 comprises a signal source 210, e.g., a frequency
synthesizer or other
suitable components as described herein, electrically coupled to a pair of
amplifiers 212, 214. The
amplifiers 212, 214 are each electrically coupled to another set of amplifiers
222, 224, respectively,
and a load coil 260 through capacitors 232, 234, respectively. Additional
components, e.g., resistors,
amplifiers, etc. may also be present but are not shown to simplify this
illustration. In use of the
generator in the driven mode, a feedback loop (see FIG. 2B below, for example)
is disabled, and the
power provided to the load coil is selected to be below a threshold value
where the transistors will fail.
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The frequency provided to the load coil 260 is scanned and tuned to a
frequency which permits
successful plasma ignition, e.g., a frequency which may maximize the coil
voltage if desired. A
detector 270, which is electrically coupled to a processor 280 through signal
converters 282, 284, may
be used to monitor the plasma. For example, the detector 270 may be configured
as an RF detector
that can be used to monitor RF signals provided to the load coil 260. In other
configurations, the
detector 270 may be configured as an optical detector, e.g., a light sensor,
fiber optic sensor or other
device, that can receive light emissions from the plasma once the plasma is
ignited. In some
embodiments, the detector 270 may be omitted and the power levels for a
particular load coil (or other
induction device) may be fixed and be set at a level to avoid transistor
breakdown. The amplifiers 252,
254 are disabled in the driven mode. In operation, the determined power level
is provided to the load
coil 260, which surrounds some portion of a torch body (not shown), and plasma
gas provided to the
torch body is ignited while the power is being applied. A plasma is generated
and sustained by
continued application of RF power from the load coil 260. In certain
embodiments, the generator may
remain in the driven mode and sample may be introduced into the plasma. During
sample introduction,
sample is typically sprayed or nebulized into the plasma along with a carrier
such as a solvent. The
plasma is operative to desolvate the sample and atomize and/or ionize the
chemical species in the
plasma.
[0097] In certain examples, once the plasma is ignited and stabilizes, it
may be desirable to switch
to the oscillation mode by enabling the oscillating circuit and disabling the
driving circuit. As noted
herein, the oscillation mode provides feedback which can be used to rapidly
adjust the impedance of
the circuit to provide impedance matching and a more stable plasma in the
torch. A schematic of
certain active components of a circuit suitable for implementing the
oscillation mode is shown in FIG.
2B. Components in FIG. 2B with similar reference numbers are the same as the
components in FIG.
2A. To switch from the driven mode to the oscillation mode, amplifiers 252,
254, which are
electrically coupled to the load coil 260 through capacitors 242, 244, are
enabled to provide feedback.
For some period, the amplifiers 212, 214, 252, 254 and the frequency
synthesizer 210 are all enabled,
which is referred to in certain instances herein as an injection-locked or
hybrid mode (see FIG. 2C and
below). The amplifiers 212, 214 and the frequency synthesizer 210 (see FIG.
2A) are then switched
off to switch the generator from the driven mode to the oscillation mode. Once
in the oscillation mode,
sample may be introduced into the plasma. The oscillation mode can provide
desirable attributes over
the driven mode during sample introduction. As sample is introduced, the
solvent may cool the plasma
and quickly alter the plasma impedance. To avoid extinguishing of the plasma,
the impedance
desirably is adjusted quickly. The feedback provided by the amplifiers 252,
254 permits rapid
adjustment of the impedance to maintain the plasma under the varying
conditions present from the time
sample is introduced, desolvated and atomized/ionized. While not described, it
is possible to ignite the
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plasma using the oscillation mode described herein. For example, if the plasma
is extinguished, the
plasma may be reignited without having to switch the circuit back to the
driven mode (though the
circuit may be switched back to the driven mode if desired to reignite the
plasma).
[00981 In certain configurations, during the transition from driven mode to
oscillation mode,
components of both modes may be enabled for some period to provide a hybrid
mode. Referring to
FIG. 2C, the feedback loop is enabled while components of the driven mode are
also enabled. In
particular, amplifiers 212, 214, 222, 224, 252 and 254 are all enabled in the
hybrid mode. As such,
power provided to the induction device 260 is a combination or hybrid of the
driven mode and the
oscillation mode. This hybrid mode may occur during the transition from driven
mode to oscillation
mode or oscillation mode or driven mode, or in other configurations, it may be
desirable to operate the
generator in the hybrid mode for certain analyses or tests. For example, the
hybrid mode may reduce
plasma phase noise so as to increase the plasma stability. Without wishing to
be bound by any one
particular theory, in the hybrid mode the plasma generator is in the
oscillation mode, but the frequency
is no longer free-running depending on the plasma impedance. Instead, the
oscillator follows a
relatively small signal injected to it at a controlled frequency. As a result,
the plasma frequency results
in a lower phase noise, and it can be controlled and optimized (if desired) by
the controller or processor
as desired. The plasma amplitude is generally still dependent on the positive
feedback path of the
oscillator because the injected signal at a controlled frequency is only a
small signal. For instance, if
methanol is loaded into the plasma, the plasma impedance will change. The
plasma will look dimmer
because methanol absorbs large amounts of energy from the plasma. For this
reason, the plasma load
coil voltages will increase because there is less plasma to the load coil.
This result provides a larger
feedback signal which will drive the oscillation-mode driver amplifiers harder
to sustain the plasma.
As a result, in the hybrid mode, the plasma energy can still react quickly to
different samples with
solvents and heavy matrices, but the frequency can be controlled by the
optimization algorithm in the
controller and is unaffected by the samples.
[0099] In certain embodiments, the amplifiers 212, 214 can be replaced with
other components to
permit switching of the generator from the driven mode to an oscillation mode
or operation of the
generator in a hybrid mode. Referring to FIG. 3A, a switched signal source
310, e.g., an RF source,
VCO, phase locked loop or other components, may be electrically coupled to a
drive amplifier 320.
The source 310 may be switched on, for example, to provide power using the
driven mode of the
generator or may be switched off to disconnect the driving circuit from the
generator. An alternative
embodiment is shown in FIG. 3B where a signal source 350, e.g., RF signal
source, VCO, etc. is
electrically coupled to a switch 360. The signal source 350 may be operated in
an "on" state
continuously when the generator is switched on, and the switch 360 may
electrically connect the signal
source 350 to the other components in the generator or may electrically
disconnect the signal source
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350 to the other components in the generator depending on the state of the
switch 360. in additional
configurations (see FIG. 4A), a signal source 410 can be electrically coupled
to a voltage controlled
oscillator 420 to provide (or not provide) a signal to the other components of
the system. For example,
depending on the voltage applied to the VCO, a measurable signal may or may
not be provided to the
other components of the generator. If desired, the amplifiers may be omitted
entirely and instead a
switchable signal source 450 (see FIG. 4B) can be used. The signal source 450
may be a high power
signal source such that no signal amplification is needed. Additional
configurations where a signal
source is electrically coupled to an induction device will be readily selected
by the person of ordinary
skill in the art, given the benefit of this disclosure.
[00100] In certain examples, a simplified schematic of certain components of a
generator is shown
in FIG. 5. The induction coil is represented by the inductor L2. A first
feedback path comprises
capacitors CS, C6. C7, C9, resistor R9, capacitor Cl 1, resistor R3, capacitor
C8, and low pass filter
L10. A second feedback path comprises capacitors C26, C27, C28, and C30,
resistor R10, capacitor
C31, resistor R6, capacitor C29, and low pass filter L20. The feedback paths
couple induction device
(L2) voltages (i.e., generator output) back to the input capacitors C25, C46
of the oscillation mode
driver amplifier M4, M6. Capacitors C11, C8, C31 and C29 can be, for example,
a combination of
fixed-value ceramic capacitors and electronically tunable varactor diodes. The
free-running frequency
of the oscillator mode is also adjustable by a processor or controller (not
shown). Capacitors Cl and
C3 are present for impedance matching. Transistors MI and M2 (and M5 and M7)
may each be
present in a single integrated circuit package, e.g., a power field effect
transistor (FET) or LDMOS
transistors, bipolar transistors, a Darlington pair or other commercially
available transistors or
components including transistors. M 1 +M2, M5+M7 are the main 1 kilo-Watt
power MOSFET to
generate RF power for the induction device L2. M3, M4, M6, M8 can be, for
example, 25 Watt (lower
power than 1 kilo-Watt) power FETs. M3 and M8 are the driven-mode driver
amplifiers, and M4 and
M6 are the oscillation-mode driver amplifiers. In using the circuit of FIG. 5
in the driven mode, the
DC voltage source V8 is switched on (e.g., to 2.7V) to turn on the gate bias
of M3 & M8, and the DC
voltage V7 is set to OV to disable M4 & M6. In the oscillation mode, the DC
voltage source V7 is
switched on (e.g., to 2.7V) to turn on the gate bias of M4 & M6, and the DC
voltage V8 is set to OV to
disable M3 & M8. For the hybrid mode. the DC voltage is set for sources V7 and
V8 (e.g., to 2.7V) to
turn on the gate bias of M3, M4, M6 & M8. V5 and V6 are the DC voltage sources
to turn on the gate
bias of the power FETs MI , M2, MS and M7 (regardless of driven, oscillation
or injection locked
mode). VS, V6, V7 and V8 are generated by an ADC (analog-to-digital
converter), which is controlled
by a processor or controller (not shown). Ti, T2 can be ferrite-core 3:1 turns-
ratio, step-down
transformers. C13 and C32 can be capacitors to tune the frequency response of
transformer Ti and
T2. Ti, T2, C13 and C32 can be omitted if desired. C2 and C4 are the high-
voltage, high-power
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capacitors. L3, 1.5, L15, L13, L9, L19 can be the RF chokes for the VDD supply
of the power
MOSFETs. L14, L16, L17, L18 can be the RF chokes for the gate (VGG) supply of
the power
MOSFETs. Gate protection diodes for Ml, M2, M5 and M7 are not shown though
they may be
present if desired. V1, V3 are the VDD DC supply for the 1-kiloWatt power FETs
Ml, M2, M5 and
M7. V2 is the VDD DC supply for the driven-mode and oscillation-mode driver
amplifiers M3, M4,
M6 and M8. While the components shown in FIG. 5 are provided for illustration
purposes, it is
possible to omit or substitute other components into the circuit and still
provide an operable generator
capable of operation in the driven mode, the oscillation mode and the hybrid
mode. In addition,
suitable circuits comprising fewer transistors, e.g., one or two transistors,
may be provided to operate
the generator in the driven mode, the oscillation mode and the hybrid mode.
[00101] In certain examples, induction devices suitable for use with the
generators described herein
may vary. In some embodiments, the induction device may comprises a load coil
comprising a wire
coiled a selected number of turns, e.g., 3-10 turns. The coiled wire provides
RF energy into the torch
to sustain the plasma. For example and referring to FIG. 6A, a torch 514 and
load coil 512 is shown
that would electrically couple to one of the generators described herein,
e.g., the load coil 512 would
be L2 in the schematic of FIG. 5. The torch 514 includes three generally
concentric tubes 514, 550,
and 548. The innermost tube 548 provides atomized flow 546 of the sample into
the plasma 516. The
middle tube 550 provides auxiliary gas flow 544 to the plasma 516. The
outermost tube 514 provides
carrier gas flow 528 for sustaining the plasma. The carrier gas flow 528 may
be directed to the plasma
516 in a laminar flow about the middle tube 550. The auxiliary gas flow 544
may be directed to the
plasma 516 within the middle tube 550 and the sample flow 546 may be directed
to the plasma 516
from a spray chamber (not shown) or other sample introduction device along the
innermost tube 548.
RF current provided to the load coil 512 from the generator may form a
magnetic field within the load
coil 512 so as to confine the plasma 516 therein. A plasma tail 598 is shown
that exits the torch 514.
In certain examples, the plasma 516 comprises a preheating zone 590, an
induction zone 592, an initial
radiation zone 594, an analytic zone 596 and a plasma tail 598. In operation
of the load coil 512, a
plasma gas may be introduced into the torch 512 and ignited. RF power from the
generator electrically
coupled to the load coil 512 may be provided in the driven mode to sustain the
plasma 516 during
ignition. In a typical plasma, argon gas may be introduced into the torch at
flow rates of about 15-20
Liters per minute. The plasma 516 may be generated using a spark or an arc to
ignite the argon gas.
The toroidal magnetic field from the induction coil 512 causes argon atoms and
ions to collide, which
results in a superheated environment, e.g., about 5,000-10,000 K or higher,
that forms the plasma 516.
Once the plasma 516 stabilizes, the generator may be switched from the driven
mode to the oscillation
mode to permit rapid adjustment of the impedance as the impedance of the
plasma 516 changes during
sample introduction through the tube 546. If desired, the generator may be
switched back to the
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driven mode or to the hybrid mode for analysis of certain samples. While the
load coil 512 is shown in
FIG. 6A as including about three turns, it will be recognized by the person of
ordinary skill in the art,
given the benefit of this disclosure, that fewer or more than three turns may
be present in the load coil
512.
[00102] In some embodiments, one or more plate electrodes may be electrically
coupled to the
generators described herein. In certain examples, the planar nature of the
plate electrodes permits
generation of a loop current in the torch body which is substantially
perpendicular to the longitudinal
axis of the torch body. The plate electrodes may be spaced symmetric from each
other where more
than two plate electrodes are present, or the plates electrodes may be
asymmetrically spaced from each
other, if desired. An illustration of two plate electrodes that can be
electrically coupled to a generator
to permit operation of the plate electrodes when the generator is in a driven
mode and an oscillation
mode is shown in FIG. 6B. The electrode 652 comprises two substantially
parallel plates 652a, 652b
positioned at a distance 'V from one another. Each of the parallel plates
652a, 652b includes an
aperture 654 through which the torch 514 may be positioned such that the torch
514, the innermost
tube 548, the middle tube 550 and the aperture 654 are aligned along a
longitudinal axis 626, which is
generally parallel to the longitudinal axis of the torch 514. The exact
dimensions and shapes of the
aperture may vary and may be any suitable dimensions and shapes that can
accept a torch. For
example, the aperture 654 may be generally circular, may be square or
rectangular shaped or may have
other shapes, e.g., may be triangular, oval, ovoid, or other suitable
geometries. In certain examples, the
aperture may be sized such that it is about 0-50% or typically about 3% larger
than the outer diameter
of the torch 514, whereas in other examples, the torch 514 may contact the
plates 652a, 652b, e.g.,
some portion of the torch may contact a surface of a plate, without any
substantial operational
problems. The aperture 654 of the electrode 552 may also include a slot 564
such that the aperture 554
is in communication with its surroundings. In use of the plates 652a, 652b, a
generator as described
herein is electrically coupled to the plates 652a, 652b. RF current is
supplied to the plates 652a, 652b
in the driven mode, oscillation mode or injection-locked mode to provide a
planar loop current, which
generates a toroidal magnetic field through the aperture 654. To ignite the
plasma, the generator is
desirably set to the driven mode (though the oscillation mode or hybrid mode
could be used to ignite
the plasma as well) and provides an RF current which generates a planar
current loop that is
substantially parallel to a radial plane, which is substantially perpendicular
to the longitudinal axis of
the torch 514. After ignition of the plasma 516, the generator may be switched
over from the driven
mode to the oscillation mode prior to introduction of sample into the torch
514. If desired, the
generator may be switched back to the driven mode or the hybrid mode for
analysis of certain samples.
Though two plate electrodes 652a, 652b are shown in FIG. 6B, a single plate
electrode can be used,
three plate electrodes can be used or more than three plate electrodes can be
used. As discussed in
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more detail below, each of the plates may be electrically coupled to the same
generator or may be
electrically coupled to a different generator if desired.
[00103] In certain embodiments, the generators described herein may be used in
combination with
another generator, which may be the same or may be different. For ease of
illustration, block diagrams
of several configurations are included herein. The term "single mode
generator" refers to a generator
which can operate in a driven mode or in an oscillation mode but is generally
not switchable between
the modes. Referring to FIG. 7, a system 700 comprising a hybrid generator 710
as described herein
and a single mode generator 720 each coupled to a load coil 730, 740,
respectively is shown. Torch
750 is positioned in the apertures of each of the load coils 730, 740. In
operation of the system 700,
the generator 710 may be used to provide power to the coil 730 in a driven
mode, an oscillation mode
or a hybrid mode. Plasma gas enters at the left of the tube 750 and arrives
axially at the coil 730 first.
The generator 720 may be configured as either a driven mode generator or an
oscillation mode
generator. In some embodiments, generator 710 is operated in the driven mode
to ignite a plasma in
the torch 750 and then generator 720 is switched on subsequent to plasma
ignition. In other
embodiments, both the generators 710, 720 may be switched on during plasma
ignition. In some
instances, generator 720 may not be switched on until the generator 710 is
switched from a driven
mode to an oscillation mode. For example, the generator 720 may be configured
as an oscillating
generator that is switched on simultaneously when the generator 710 is
switched from a driven mode to
an oscillation mode. In some embodiments, the generator 710 may be used in an
oscillation mode to
desolvate sample, and the generator 720 may be a driven mode generator used to
atomize/ionize the
sample. In other embodiments, the generator 710 may be used in an oscillation
mode to desolvate
sample, and the generator 720 may be an oscillation generator used to
atomize/ionize the sample. In
additional embodiments, the generator 710 may be used in a driven mode to
desolvate sample, and the
generator 720 may be a driven mode generator used to atomize/ionize the
sample. In certain
embodiments, the generator 710 may be used in a driven mode to desolvate
sample, and the generator
720 may be an oscillation generator used to atomize/ionize the sample. If
desired, the number of coils
in the load coils 730, 740 may be different or may be the same.
[00104] In certain examples, another system is shown in FIG. 8 where a single
mode generator is
positioned upstream of a hybrid generator, e.g., one that can be operated in a
driven mode, an
oscillation mode and/or a hybrid mode, as described herein. The system 800
comprises a single mode
generator 810 and a hybrid generator 820 each coupled to a load coil 830, 840,
respectively. Torch
850 is positioned in the apertures of each of the load coils 830, 840. In
operation of the system 800,
the generator 820 may be used to provide power to the coil 840 in a driven
mode, an oscillation mode
or a hybrid mode. Plasma gas enters at the left of the tube 850 and arrives
axially at the coil 830 first.
The generator 810 may be configured as either a driven mode generator or an
oscillation mode
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generator. In some embodiments, generator 820 is operated in the driven mode
to ignite a plasma in
the torch 850 and then generator 810 is switched on subsequent to plasma
ignition. In other
embodiments, both the generators 810, 820 may be switched on during plasma
ignition. In some
instances, generator 810 may not be switched on until the generator 820 is
switched from a driven
mode to an oscillation mode. For example, the generator 810 may be configured
as an oscillating
generator that is switched on simultaneously when the generator 820 is
switched from a driven mode to
an oscillation mode. In some embodiments, the generator 810 may be an
oscillation generator to
desolvate sample, and the generator 820 may be operated in a driven mode to
atomize/ionize the
sample. In certain embodiments, the generator 810 may be an oscillation
generator to desolvate
sample, and the generator 820 may be operated in an oscillation mode to
atomize/ionize the sample.
In other embodiments, the generator 810 may be a driven mode generator, and
the generator 820 may
be operated in a driven mode to atomize/ionize the sample. In additional
embodiments, the generator
810 may be a driven mode generator, and the generator 820 may be operated in
an oscillation mode to
atomize/ionize the sample. If desired, the number of coils in the load coils
830, 840 may be different
or may be the same.
[00105] In certain examples, another system is shown in FIG. 9 where two
hybrid generators, as
described herein, are present. The system 900 comprises a first hybrid
generator 910 and a second
hybrid generator 920 each coupled to a load coil 930, 940, respectively. Torch
950 is positioned in the
apertures of each of the load coils 930, 940. In operation of the system 900,
each of generators
910,920 may be used to provide power to the coils 930, 940, respectively, in a
driven mode, an
oscillation mode or a hybrid mode. Plasma gas enters at the left of the tube
950 and arrives axially at
the coil 930 first. In some embodiments, each of the generators 910, 920 is
operated in the driven
mode during plasma ignition. In other embodiments, only one of the generators
910, 920 is operated in
the driven mode during plasma ignition, and the other generator may be
switched off or may be
operated in the oscillation mode. Subsequent to plasma ignition, one or both
of the generators 910, 920
may be switched from a driven mode to an oscillation mode. For example,
generator 910 may remain
operated in a driven mode and generator 920 may be switched to an oscillation
mode. In a different
configuration, generator 910 is switched to an oscillation mode and generator
920 remains in the driven
mode. In another configuration, generators 910, 920 are each switched to an
oscillation mode, though
they may be switched at the same time or generator 910 may first be switched
to an oscillation mode
followed by switching of generator 920 to an oscillation mode (or vice versa).
[00106] In certain embodiments where more than a single generator is present,
each generator may
be independently electrically coupled to one, two, three or more plate
electrodes. Illustrations using
two plate electrodes for convenience purposes are shown in FIGS. 10-12.
Referring to FIG. 10, a
system 1000 comprising a hybrid generator 1010 as described herein and a
single mode generator 1020
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each coupled to a pair of plate electrodes 1030, 1040, respectively is shown.
The plate electrodes
1030, 1040 are shown coupled to a respective mounting plate 1035, 1045. Torch
1050 is positioned in
the apertures of each of the plates 1030, 1040. In operation of the system
1000, the generator 1010
may be used to provide power to the plates 1030 in a driven mode, an
oscillation mode or a hybrid
mode. Plasma gas enters at the left of the tube 1050 and arrives axially at
the plates 1030 first. The
generator 1020 may be configured as either a driven mode generator or an
oscillation mode generator.
In some embodiments, generator 1010 is operated in the driven mode to ignite a
plasma in the torch
1050 and then generator 1020 is switched on subsequent to plasma ignition. In
other embodiments,
both the generators 1010, 1020 may be switched on during plasma ignition. In
some instances,
generator 1020 may not be switched on until the generator 1010 is switched
from a driven mode to an
oscillation mode. For example, the generator 1020 may be configured as an
oscillating generator that
is switched on simultaneously when the generator 1010 is switched from a
driven mode to an
oscillation mode. In some embodiments, the generator 1010 may be used in an
oscillation mode to
desolvate sample, and the generator 1020 may be a driven mode generator used
to atomize/ionize the
sample. In other embodiments, the generator 1010 may be used in an oscillation
mode to desolvate
sample, and the generator 1020 may be an oscillation generator used to
atomize/ionize the sample. In
additional embodiments, the generator 1010 may be used in a driven mode to
desolvate sample, and the
generator 1020 may be a driven mode generator used to atomize/ionize the
sample. In certain
embodiments, the generator 1010 may be used in a driven mode to desolvate
sample, and the generator
1020 may be an oscillation generator used to atomize/ionize the sample.
[00107] In certain embodiments, another system is shown in FIG. 11 where a
single mode generator
is positioned upstream of a hybrid generator as described herein. The system
1100 comprises a single
mode generator 1110 and a hybrid generator 1120 each coupled to a pair of
plate electrodes 1130,
1140, respectively. The plate electrodes 1130, 1140 are shown coupled to a
mounting plate 1135,
1145, respectively. Torch 1150 is positioned in the apertures of each of the
plate electrodes 1130,
1140. In operation of the system 1100, the generator 1120 may be used to
provide power to the plates
1140 in a driven mode, an oscillation mode or a hybrid mode. Plasma gas enters
at the left of the tube
1150 and arrives axially at the plates 1130 first. The generator 1110 may be
configured as either a
driven mode generator or an oscillation mode generator. In some embodiments,
generator 1120 is
operated in the driven mode to ignite a plasma in the torch 1150 and then
generator 1110 is switched
on subsequent to plasma ignition. In other embodiments, both the generators
1110, 1120 may be
switched on during plasma ignition. In some instances, generator 1110 may not
be switched on until
the generator 1120 is switched from a driven mode to an oscillation mode. For
example, the generator
1110 may be configured as an oscillating generator that is switched on
simultaneously when the
generator 1120 is switched from a driven mode to an oscillation mode. In some
embodiments, the
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generator 1110 may be an oscillation generator to desolvate sample, and the
generator 1120 may be
operated in a driven mode to atomize/ionize the sample. In certain
embodiments, the generator 1110
may be an oscillation generator to desolvate sample, and the generator 1120
may be operated in an
oscillation mode to atomize/ionize the sample. In other embodiments, the
generator 1110 may be a
driven mode generator, and the generator 1120 may be operated in a driven mode
to atomize/ionize the
sample. In additional embodiments, the generator 1110 may be a driven mode
generator, and the
generator 1120 may be operated in an oscillation mode to atomize/ionize the
sample.
[00108] In certain examples, another system is shown in FIG. 12 where two
hybrid generators, as
described herein, are present. The system 1200 comprises a first hybrid
generator 1210 and a second
hybrid generator 1220 each coupled to a pair of plate electrodes 1230, 1240,
respectively. The plate
electrodes 1230, 1240 are shown coupled to a respective mounting plate 1235,
1245. Torch 1250 is
positioned in the apertures of each of the plate electrodes 1230, 1240. In
operation of the system 1200,
each of generators 1210, 1220 may be used to provide power to the plates 1230,
1240, respectively, in
a driven mode, an oscillation mode or a hybrid mode. Plasma gas enters at the
left of the torch 1250
and arrives axially at the coil 1230 first. In some embodiments, each of the
generators 1210, 1220 is
operated in the driven mode during plasma ignition. In other embodiments, only
one of the generators
1210, 1220 is operated in the driven mode during plasma ignition, and the
other generator may be
switched off or may be operated in the oscillation mode. Subsequent to plasma
ignition, one or both of
the generators 1210, 1220 may be switched from a driven mode to an oscillation
mode. For example,
generator 1210 may remain operated in a driven mode and generator 1220 may be
switched to an
oscillation mode. In a different configuration. generator 1210 is switched to
an oscillation mode and
generator 1220 remains in the driven mode. In another configuration,
generators 1210, 1220 are each
switched to an oscillation mode, though they may be switched at the same time
or generator 1210 may
first be switched to an oscillation mode followed by switching of generator
1220 to an oscillation mode
(or vice versa).
[00109] In certain embodiments where more than a single generator is present,
one generator may
be independently electrically coupled to one, two, three or more plate
electrodes and the other
generator may be electrically coupled to a load coil. Illustrations using two
plate electrodes for
convenience purposes are shown in FIGS. 13-18. Referring to FIG. 13, a system
1300 comprising a
hybrid generator 1310 as described herein and a single mode generator 1320.
The generator 1310 is
electrically coupled to a load coil 1330, and the generator 1320 is
electrically coupled to plate electrode
1340. The plate electrodes 1340 are shown coupled to a mounting plate 1345.
Torch 1350 is
positioned in the apertures of the load coil 1330 and the plates 1340. In
operation of the system 1300,
the generator 1310 may be used to provide power to the coil 1330 in a driven
mode, an oscillation
mode or a hybrid mode. Plasma gas enters at the left of the tube 1350 and
arrives axially at the coil
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1330 first. The generator 1320 may be configured as either a driven mode
generator or an oscillation
mode generator. In some embodiments, the generator 1310 is operated in the
driven mode to ignite a
plasma in the torch 1350 and then generator 1320 is switched on subsequent to
plasma ignition. In
other embodiments, both the generators 1310, 1320 may be switched on during
plasma ignition. In
some instances, generator 1320 may not be switched on until the generator 1310
is switched from a
driven mode to an oscillation mode. For example, the generator 1320 may be
configured as an
oscillating generator that is switched on simultaneously when the generator
1310 is switched from a
driven mode to an oscillation mode. In some embodiments, the generator 1310
may be used in an
oscillation mode to desolvate sample, and the generator 1320 may be a driven
mode generator used to
atomize/ionize the sample. In other embodiments, the generator 1310 may be
used in an oscillation
mode to desolvate sample, and the generator 1320 may be an oscillation
generator used to
atomize/ionize the sample. In additional embodiments, the generator 1310 may
be used in a driven
mode to desolvate sample, and the generator 1320 may be a driven mode
generator used to
atomize/ionize the sample. In certain embodiments, the generator 1310 may be
used in a driven mode
to desolvate sample, and the generator 1320 may be an oscillation generator
used to atomize/ionize the
sample.
[00110] In certain examples, another system is shown in FIG. 14 where a single
mode generator is
positioned upstream of a hybrid generator as described herein. The system 1400
comprises a single
mode generator 1410 and a hybrid generator 1420. The generator 1410 is
electrically coupled to a load
coil 1430, and the generator 1420 is electrically coupled to plate electrodes
1440. The plate electrodes
1440 are shown coupled to a mounting plate 1445. Torch 1150 is positioned in
the apertures of each of
the load coil 1430 and the plate electrodes 1440. In operation of the system
1400, the generator 1420
may be used to provide power to the plates 1440 in a driven mode, an
oscillation mode or a hybrid
mode. Plasma gas enters at the left of the tube 1450 and arrives axially at
the coil 1430 first. The
generator 1410 may be configured as either a driven mode generator or an
oscillation mode generator.
In some embodiments, generator 1420 is operated in the driven mode to ignite a
plasma in the torch
1450 and then generator 1410 is switched on subsequent to plasma ignition. In
other embodiments,
both the generators 1410, 1420 may be switched on during plasma ignition. In
some instances,
generator 1410 may not be switched on until the generator 1420 is switched
from a driven mode to an
oscillation mode. For example, the generator 1410 may be configured as an
oscillating generator that
is switched on simultaneously when the generator 1420 is switched from a
driven mode to an
oscillation mode. In some embodiments, the generator 1410 may be an
oscillation generator to
desolvate sample, and the generator 1420 may be operated in a driven mode to
atomize/ionize the
sample. In certain embodiments, the generator 1410 may be an oscillation
generator to desolvate
sample, and the generator 1420 may be operated in an oscillation mode to
atomize/ionize the sample.
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In other embodiments, the generator 1410 may be a driven mode generator, and
the generator 1420
may be operated in a driven mode to atomize/ionize the sample. In additional
embodiments, the
generator 1410 may be a driven mode generator, and the generator 1420 may be
operated in an
oscillation mode to atomize/ionize the sample.
[00111] In certain examples, another system is shown in FIG. 15 where two
hybrid generators, as
described herein, are present. The system 1500 comprises a first hybrid
generator 1510 and a second
hybrid generator 1520. The generator 1510 is electrically coupled to a load
coil 1530, and the
generator 1520 is electrically coupled to plate electrodes 1540. The plate
electrodes 1540 are shown
coupled to a mounting plate 1545. Torch 1550 is positioned in the apertures of
each of the load coil
1530 and the plate electrodes 1540. In operation of the system 1500, each of
generators 1510, 1520
may be used to provide power to the plates 1530, 1540, respectively, in a
driven mode, an oscillation
mode or a hybrid mode. Plasma gas enters at the left of the torch 1550 and
arrives under the coil 1530
first. In some embodiments. each of the generators 1510, 1520 is operated in
the driven mode during
plasma ignition. In other embodiments, only one of the generators 1510, 1520
is operated in the driven
mode during plasma ignition, and the other generator may be switched off or
may be operated in the
oscillation mode. Subsequent to plasma ignition, one or both of the generators
1510, 1520 may be
switched from a driven mode to an oscillation mode. For example, generator
1510 may remain
operated in a driven mode and generator 1520 may be switched to an oscillation
mode. In a different
configuration, generator 1510 is switched to an oscillation mode and generator
1520 remains in the
driven mode. In another configuration, generators 1510, 1520 are each switched
to an oscillation
mode, though they may be switched at the same time or generator 1510 may first
be switched to an
oscillation mode followed by switching of generator 1520 to an oscillation
mode (or vice versa).
[00112] Referring to FIG. 16, a system 1600 is shown comprising a hybrid
generator 1610 as
described herein and a single mode generator 1620. The generator 1610 is
electrically coupled to plate
electrodes 1630, and the generator 1620 is electrically coupled to a load coil
1640. The plate
electrodes 1630 are shown coupled to a mounting plate 1645. Torch 1650 is
positioned in the apertures
of the load coil 1640 and the plates 1630. In operation of the system 1600,
the generator 1610 may be
used to provide power to the plates 1630 in a driven mode, an oscillation mode
or a hybrid mode.
Plasma gas enters at the left of the tube 1650 and arrives axially at the
plates 1630 first. The generator
1620 may be configured as either a driven mode generator or an oscillation
mode generator. In some
embodiments, the generator 1610 is operated in the driven mode to ignite a
plasma in the torch 1650
and then generator 1620 is switched on subsequent to plasma ignition. In other
embodiments, both the
generators 1610, 1620 may be switched on during plasma ignition. In some
instances. generator 1620
may not be switched on until the generator 1610 is switched from a driven mode
to an oscillation
mode. For example, the generator 1620 may be configured as an oscillating
generator that is switched
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on simultaneously when the generator 1610 is switched from a driven mode to an
oscillation mode. In
some embodiments, the generator 1610 may be used in an oscillation mode to
desolvate sample, and
the generator 1620 may be a driven mode generator used to atomize/ionize the
sample. In other
embodiments, the generator 1610 may be used in an oscillation mode to
desolvate sample, and the
generator 1620 may be an oscillation generator used to atomize/ionize the
sample. In additional
embodiments, the generator 1610 may be used in a driven mode to desolvate
sample, and the generator
1620 may be a driven mode generator used to atomize/ionize the sample. In
certain embodiments, the
generator 1610 may be used in a driven mode to desolvate sample, and the
generator 1620 may be an
oscillation generator used to atomize/ionize the sample.
[00113] In certain examples, another system is shown in FIG. 17 where a single
mode generator is
positioned upstream of a hybrid generator as described herein. The system 1700
comprises a single
mode generator 1710 and a hybrid generator 1720. The generator 1710 is
electrically coupled to plate
electrodes 1730, and the generator 1720 is electrically coupled to a load coil
1740. The plate
electrodes 1730 are shown coupled to a mounting plate 1745. Torch 1750 is
positioned in the apertures
of each of the load coil 1740 and the plate electrodes 1730. In operation of
the system 1700, the
generator 1720 may be used to provide power to the load coil 1740 in a driven
mode, an oscillation
mode or a hybrid mode. Plasma gas enters at the left of the tube 1750 and
arrives axially at the plates
1730 first. The generator 1710 may be configured as either a driven mode
generator or an oscillation
mode generator. In some embodiments, generator 1720 is operated in the driven
mode to ignite a
plasma in the torch 1750 and then generator 1710 is switched on subsequent to
plasma ignition. In
other embodiments, both the generators 1710, 1720 may be switched on during
plasma ignition. In
some instances, generator 1710 may not be switched on until the generator 1720
is switched from a
driven mode to an oscillation mode. For example, the generator 1710 may be
configured as an
oscillating generator that is switched on simultaneously when the generator
1720 is switched from a
driven mode to an oscillation mode. In some embodiments, the generator 1710
may be an oscillation
generator to desolvate sample, and the generator 1720 may be operated in a
driven mode to
atomize/ionize the sample. In certain embodiments, the generator 1710 may be
an oscillation generator
to desolvate sample, and the generator 1720 may be operated in an oscillation
mode to atomize/ionize
the sample. In other embodiments, the generator 1710 may be a driven mode
generator, and the
generator 1720 may be operated in a driven mode to atomize/ionize the sample.
In additional
embodiments, the generator 1710 may be a driven mode generator, and the
generator 1720 may be
operated in an oscillation mode to atomize/ionize the sample.
[00114] In certain examples, another system is shown in FIG. 18 where two
hybrid generators, as
described herein, are present. The system 1800 comprises a first hybrid
generator 1810 and a second
hybrid generator 1820. The generator 1810 is electrically coupled to plate
electrodes 1830, and the
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generator 1820 is electrically coupled to a load coil 1840. The plate
electrodes 1830 are shown
coupled to a mounting plate 1845. Torch 1850 is positioned in the apertures of
each of the load coil
1840 and the plate electrodes 1830. In operation of the system 1800, each of
generators 1810, 1820
may be used to provide power to the plates 1830, and load coil 1840,
respectively, in a driven mode, an
oscillation mode or a hybrid mode. Plasma gas enters at the left of the torch
1850 and arrives axially at
the plates 1830 first. In some embodiments, each of the generators 1810, 1820
is operated in the
driven mode during plasma ignition. In other embodiments, only one of the
generators 1810, 1820 is
operated in the driven mode during plasma ignition, and the other generator
may be switched off or
may be operated in the oscillation mode. Subsequent to plasma ignition, one or
both of the generators
1810, 1820 may be switched from a driven mode to an oscillation mode. For
example, generator 1810
may remain operated in a driven mode and generator 1820 may be switched to an
oscillation mode. In
a different configuration, generator 1810 is switched to an oscillation mode
and generator 1820
remains in the driven mode. In another configuration, generators 1810, 1820
are each switched to an
oscillation mode, though they may be switched at the same time or generator
1810 may first be
switched to an oscillation mode followed by switching of generator 1820 to an
oscillation mode (or
vice versa).
[00115] In certain examples, a single hybrid generator as described herein may
be used to provide
power to two or more induction devices at the same time. Referring to FIG. 19,
a system 1900
comprises a generator 1910 electrically coupled to load coils 1930, 1940. A
torch 1950 is positioned in
an aperture of the load coils 1930, 1940. In operation of the system 1900, one
or both of the load coils
1930, 1940 may be provided power in a driven mode, an oscillation mode or
both. In some examples,
it may be desirable to ignite the plasma by switching on only load coil 1930
when the generator 1910 is
in a driven mode. As the generator 1910 is switched to the oscillation mode,
load coil 1940 may also
be powered on to increase the overall length of the plasma in the torch 1950.
Alternatively, it may be
desirable to ignite the plasma by switching on both loads coils 1930, 1940
when the generator 1910 is
in a driven mode. Once the plasma is ignited, the generator 1910 may be
switched to an oscillation
mode and both of load coils 1930, 1940 may be active or one of the load coils
1930, 1940 may be
switched off, if desired. Suitable circuitry may be present in the generator
such that different powers
are provided to the load coils 1930, 1940 from the generator 1910. For
example, it may be desirable to
provide more power to the load coil 1930 than the load coil 1940 (or vice
versa). In some
embodiments, the load coil 1940 may comprise a different number of turns than
the load coil 1930,
whereas in other examples, the numbers of turns may be the same in each of the
load coils 1930, 1940.
[00116] In certain embodiments. a similar system as shown in FIG. 19 but
including two sets of
plate electrodes is shown in FIG. 20. The system 2000 comprises a generator
2010 electrically coupled
to plate electrodes 2030, 2040. A torch 2050 is positioned in an aperture of
the plate electrodes 2030,
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2040. In operation of the system 2000, one or both of the pairs of plate
electrodes 2030, 2040 may be
provided power in a driven mode, an oscillation mode or both. In some
examples, it may be desirable
to ignite the plasma by switching on only plate electrodes 2030 when the
generator 2010 is in a driven
mode. As the generator 2010 is switched to the oscillation mode, electrodes
2040 may also be
powered on to increase the overall length of the plasma in the torch 2050.
Alternatively, it may be
desirable to ignite the plasma by switching on both sets of plate electrodes
2030, 2040 when the
generator 2010 is in a driven mode. Once the plasma is ignited, the generator
2010 may be switched to
an oscillation mode and both of sets of plate electrodes 2030, 2040 may be
active or one of the sets of
plate electrodes 2030, 2040 may be switched off, if desired. Suitable
circuitry may be present in the
generator such that different powers are provided to the sets of plate
electrodes 2030, 2040 from the
generator 2010. For example, it may be desirable to provide more power to the
electrodes 2030 than
the electrodes 2040 (or vice versa). In certain examples, the electrodes 2040
may comprise a different
number of plates than the electrodes 2030, whereas in other examples, the
numbers of plates may be
the same in each of the electrodes 2030, 2040.
[00117] In certain examples, a similar system as shown in FIGS. 19 and 20 but
including one load
coil and one set of plate electrodes is shown in FIG. 21. The system 2100
comprises a generator 2110
electrically coupled to a load coil 2130 and plate electrodes 2140. A torch
2150 is positioned in an
aperture of the load coil 2130 and the plate electrodes 2140. In operation of
the system 2100, one or
both of the load coil 2130 and the plate electrodes 2140 may be provided power
in a driven mode, an
oscillation mode or both. In some examples, it may be desirable to ignite the
plasma by switching on
only load coil 2130 when the generator 2110 is in a driven mode. As the
generator 2110 is switched to
the oscillation mode, plate electrodes 2140 may also be powered on to increase
the overall length of the
plasma in the torch 2150. Alternatively, it may be desirable to ignite the
plasma by switching on both
the load coil 2130 and the plate electrodes 2140 when the generator 2110 is in
a driven mode. Once
the plasma is ignited, the generator 2110 may be switched to an oscillation
mode and both the load coil
2130 and the plate electrodes 2140 may be active or one of the load coil 2130
or the plate electrodes
2140 may be switched off, if desired. Suitable circuitry may be present in the
generator such that
different powers are provided to the load coil 2130 and the plate electrodes
2140 from the generator
2110. For example, it may be desirable to provide more power to the induction
coil 2130 than the plate
electrodes 2140 (or vice versa).
[00118] In certain examples, a similar system as shown in FIGS. 19-21 but
including a set of plate
electrodes upstream of a load coil is shown in FIG. 22. The system 2200
comprises a generator 2210
electrically coupled to plate electrodes 2230 and a load coil 2240. A torch
2250 is positioned in an
aperture of the plate electrodes 2230 and the load coil 2240. In operation of
the system 2200, one or
both of the plate electrode 2230 and the load coil 2240 may be provided power
in a driven mode, an
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oscillation mode or both. In some examples, it may be desirable to ignite the
plasma by switching on
only the plate electrodes 2230 when the generator 2210 is in a driven mode. As
the generator 2210 is
switched to the oscillation mode, the load coil 2240 may also be powered on to
increase the overall
length of the plasma in the torch 2250. Alternatively, it may be desirable to
ignite the plasma by
switching on both the plate electrodes 2230 and the load coil 2240 when the
generator 2210 is in a
driven mode. Once the plasma is ignited, the generator 2210 may be switched to
an oscillation mode
and both the plate electrodes 2230 and the load coil 2240 may be active or one
of the plate electrodes
2230 or the load coil 2240 may be switched off, if desired. Suitable circuitry
may be present in the
generator such that different powers are provided to the plate electrodes 2230
and the load coil 2240
from the generator 2210. For example, it may be desirable to provide more
power to the plate
electrodes 2230 than the load coil 2240 (or vice versa).
1001191 In certain examples, the hybrid generators described herein can be
used to power an
inductively coupled plasma (ICP) that is present in an optical emission system
(OES). Illustrative
components of an OES are shown in FIG. 23. The device 2300 includes a sample
introduction system
2330 fluidically coupled to an ICP 2340. The ICP 2340 is electrically coupled
to a generator 2335 and
may be generated using a torch, load coil (or plates) or other induction
devices. The generator 2335
may be any of the hybrid generators described herein. The ICP 2340 is
fluidically (or optically or
both) coupled to a detector 2350. The sample introduction device 2330 may vary
depending on the
nature of the sample. In certain examples, the sample introduction device 2330
may be a nebulizer that
is configured to aerosolize liquid sample for introduction into the ICP 2340.
In other examples, the
sample introduction device 2330 may be configured to directly inject sample
into the ICP 2340. Other
suitable devices and methods for introducing samples will be readily selected
by the person of ordinary
skill in the art, given the benefit of this disclosure. The detector 2350 can
take numerous forms and
may be any suitable device that may detect optical emissions, such as optical
emission 2355. For
example, the detector 2350 may include suitable optics, such as lenses,
mirrors, prisms, windows,
band-pass filters, etc. The detector 2350 may also include gratings, such as
echelle gratings, to provide
a multi-channel OES device. Gratings such as echelle gratings may allow for
simultaneous detection of
multiple emission wavelengths. The gratings may be positioned within a
monochromator or other
suitable device for selection of one or more particular wavelengths to
monitor. In certain examples, the
detector 2350 may include a charge coupled device (CCD). In other examples,
the OES device may be
configured to implement Fourier transforms to provide simultaneous detection
of multiple emission
wavelengths. The detector 2350 can be configured to monitor emission
wavelengths over a large
wavelength range including, but not limited to, ultraviolet, visible, near and
far infrared, etc. The OES
device 2300 may further include suitable electronics such as a microprocessor
and/or computer and
suitable circuitry to provide a desired signal and/or for data acquisition.
Suitable additional devices and
CA 03022428 2018-10-26
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circuitry are known in the art and may be found, for example, on commercially
available OES devices
such as Optima 2100DV series, Optima 5000 DV series and Optima 7000 series OES
devices
commercially available from PerkinElmer Health Sciences, Inc. (Waltham, MA).
The optional
amplifier 2360 may be operative to increase a signal 2355, e.g., amplify the
signal from detected
photons, and can provide the signal to a an optional display 2370, which may
be a readout, computer,
etc. In examples where the signal 2355 is sufficiently large for display or
detection, the amplifier 2360
may be omitted. In certain examples, the amplifier 2360 is a photomultiplier
tube configured to
receive signals from the detector 2350. Other suitable devices for amplifying
signals, however, will be
selected by the person of ordinary skill in the art, given the benefit of this
disclosure. It will also be
within the ability of the person of ordinary skill in the art, given the
benefit of this disclosure, to retrofit
existing OES devices with the generator 2335 and to design new OES devices
using the generators
disclosed here. The OES device 2300 may further include autosamplers, such as
AS90 and AS93
autosamplers commercially available from PerkinElmer Health Sciences or
similar devices available
from other suppliers.
[00120] In certain embodiments, the generators described herein can be used in
an instrument
designed for absorption spectroscopy (AS). Atoms and ions may absorb certain
wavelengths of light to
provide energy for a transition from a lower energy level to a higher energy
level. An atom or ion may
contain multiple resonance lines resulting from transition from a ground state
to a higher energy level.
The energy needed to promote such transitions may be supplied using numerous
sources, e.g., heat,
flames, plasmas, arc, sparks, cathode ray lamps, lasers, etc., as discussed
further below. In some
examples, the generator described herein can be used to power an ICP to
provide the energy or light
that is absorbed by the atoms or ions. In certain examples, a single beam AS
device is shown in FIG.
24. The single beam AS device 2400 includes a power source 2410, a lamp 2420,
a sample
introduction device 2425, an 1CP device 2430 electrically coupled to a hybrid
generator 2435, a
detector 2440, an optional amplifier 2450 and an optional display 2460. The
power source 2410 may
be configured to supply power to the lamp 2420, which provides one or more
wavelengths of light
2422 for absorption by atoms and ions. If desired the power source 2410 may
also be electrically
coupled to the generator 2435. Suitable lamps include, but are not limited to
mercury lamps, cathode
ray lamps, lasers, etc. The lamp may be pulsed using suitable choppers or
pulsed power supplies, or in
examples where a laser is implemented, the laser may be pulsed with a selected
frequency, e.g. 5, 10,
or 20 times/second. The exact configuration of the lamp 2420 may vary. For
example, the lamp 2420
may provide light axially along the ICP 2430 or may provide light radially
along the ICP device 2430.
The example shown in FIG. 24 is configured for axial supply of light from the
lamp 2420. There can
be signal-to-noise advantages using axial viewing of signals. The ICP 2430 may
be sustained using any
of the induction devices and torches described herein or other suitable
induction devices and torches
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that may be readily selected or designed by the person of ordinary skill in
the art, given the benefit of
this disclosure. As sample is atomized and/or ionized in the TCP 2430, the
incident light 2422 from the
lamp 2420 may excite atoms. That is, some percentage of the light 2422 that is
supplied by the lamp
2420 may be absorbed by the atoms and ions in the TCP 2430. The remaining
percentage of the light
2435 may be transmitted to the detector 2440. The detector 2440 may provide
one or more suitable
wavelengths using, for example, prisms, lenses, gratings and other suitable
devices such as those
discussed above in reference to the OES devices, for example. The signal may
be provided to the
optional amplifier 2450 for increasing the signal provided to the display
2460. To account for the
amount of absorption by sample in the 'CP 2430, a blank, such as water, may be
introduced prior to
sample introduction to provide a 100% transmittance reference value. The
amount of light transmitted
once sample is introduced into the TCP or exits from the TCP may be measured,
and the amount of light
transmitted with sample may be divided by the reference value to obtain the
transmittance. The
negative logo of the transmittance is equal to the absorbance. The AS device
2400 may further include
suitable electronics such as a microprocessor and/or computer and suitable
circuitry to provide a
desired signal and/or for data acquisition. Suitable additional devices and
circuitry may be found, for
example, on commercially available AS devices such as AAnalyst series
spectrometers commercially
available from PerkinElmer Health Sciences. It will also be within the ability
of the person of ordinary
skill in the art, given the benefit of this disclosure, to retrofit existing
AS devices with the generators
disclosed here and to design new AS devices using the generators disclosed
herein. The AS devices
may further include autosamplers known in the art, such as AS-90A, AS-90p1us
and AS-93p1u5
autosamplers commercially available from PerkinElmer Health Sciences.
[00121] In certain embodiments and referring to FIG. 25, the generators
described herein can be
used in a dual beam AS device 2500 includes a power source 2510, a lamp 2520,
a TCP 2565, a
generator 2566 electrically coupled to an induction device (not shown) of the
TCP 2565, a detector
2580, an optional amplifier 2590 and an optional display 2595. The power
source 2510 may be
configured to supply power to the lamp 2520, which provides one or more
wavelengths of light 2525
for absorption by atoms and ions. Suitable lamps include, but are not limited
to, mercury lamps,
cathode ray lamps, lasers, etc. The lamp may be pulsed using suitable choppers
or pulsed power
supplies, or in examples where a laser is implemented, the laser may be pulsed
with a selected
frequency, e.g. 5, 10 or 20 times/second. The configuration of the lamp 2520
may vary. For example,
the lamp 2520 may provide light axially along the TCP 2565 or may provide
light radially along the
ICP 2565. The example shown in FIG. 25 is configured for axial supply of light
from the lamp 2520.
There may be signal-to-noise advantages using axial viewing of signals. The
TCP 2565 may be any of
the TCPs discussed herein or other suitable TCPs that may be readily selected
or designed by the person
of ordinary skill in the art, given the benefit of this disclosure. As sample
is atomized and/or ionized in
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the TCP 2565, the incident light 2525 from the lamp 2520 may excite atoms.
That is, some percentage
of the light 2525 that is supplied by the lamp 2520 may be absorbed by the
atoms and ions in the 1CP
2565. The remaining percentage of the light 2567 is transmitted to the
detector 2580. In examples
using dual beams, the incident light 2525 may be split using a beam splitter
2530 such that some
percentage of light, e.g., about 10% to about 90%, may be transmitted as a
light beam 2535 to the ICP
2565 and the remaining percentage of the light may be transmitted as a light
beam 2540 to mirrors or
lenses 2550 and 2555. The light beams may be recombined using a combiner 2570,
such as a half-
silvered mirror, and a combined signal 2575 may be provided to the detection
device 2580. The ratio
between a reference value and the value for the sample may then be determined
to calculate the
absorbance of the sample. The detection device 2580 may provide one or more
suitable wavelengths
using, for example, prisms, lenses, ratings and other suitable devices known
in the art, such as those
discussed above in reference to the OES devices, for example. Signal 2585 may
be provided to the
optional amplifier 2590 for increasing the signal to provide to the display
2595. The AS device 2500
may further include suitable electronics known in the art, such as a
microprocessor and/or computer
and suitable circuitry to provide a desired signal and/or for data
acquisition. Suitable additional devices
and circuitry may be found, for example, on commercially available AS devices
such as AAnalyst
series spectrometers commercially available from PerkinElmer Health Sciences,
Inc. It will be within
the ability of the person of ordinary skill in the art, given the benefit of
this disclosure, to retrofit
existing dual beam AS devices with the generators disclosed here and to design
new dual beam AS
devices using the generators disclosed herein. The AS devices may further
include autosamplers
known in the art, such as AS-90A, AS-90p1us and AS-93p1us autosamplers
commercially available
from PerkinElmer Health Sciences, Inc.
[00122] In certain embodiments, the generators described herein can be used in
a mass
spectrometer. An illustrative MS device is shown in FIG. 26. The MS device
2600 includes a sample
introduction device 2610, an ionization device 2620 (labeled as ICP)
electrically coupled to a generator
2625, a mass analyzer 2630, a detection device 2640, a processing device 2650
and an optional display
2660. The sample introduction device 2610, ionization device 2620, the mass
analyzer 2630 and the
detection device 2640 may be operated at reduced pressures using one or more
vacuum pumps. In
certain examples, however, only the mass analyzer 2630 and the detection
device 2640 may be
operated at reduced pressures. The sample introduction device 2610 may include
an inlet system
configured to provide sample to the ionization device 2620. The inlet system
may include one or more
batch inlets, direct probe inlets and/or chromatographic inlets. The sample
introduction device 2610
may be an injector, a nebulizer or other suitable devices that may deliver
solid, liquid or gaseous
samples to the ionization device 2620. The ionization device 2620 may be an
inductively coupled
plasma generated and/or sustained using the generator 2625, e.g., using a
hybrid generator as described
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herein. If desired, the ionization device can be coupled to another ionization
device, e.g., another
device which can atomize and/or ionize a sample including, for example, plasma
(inductively coupled
plasmas, capacitively coupled plasmas, microwave-induced plasmas, etc.), arcs,
sparks, drift ion
devices, devices that can ionize a sample using gas-phase ionization (electron
ionization, chemical
ionization, desorption chemical ionization, negative-ion chemical ionization),
field desorption devices,
field ionization devices, fast atom bombardment devices, secondary ion mass
spectrometry devices,
electrospray ionization devices, probe electrospray ionization devices, sonic
spray ionization devices,
atmospheric pressure chemical ionization devices, atmospheric pressure
photoionization devices,
atmospheric pressure laser ionization devices, matrix assisted laser
desorption ionization devices,
aerosol laser desorption ionization devices, surface-enhanced laser desorption
ionization devices, glow
discharges, resonant ionization, thermal ionization, thermospray ionization,
radioactive ionization, ion-
attachment ionization, liquid metal ion devices, laser ablation electrospray
ionization, or combinations
of any two or more of these illustrative ionization devices. The mass analyzer
2630 may take
numerous forms depending generally on the sample nature, desired resolution,
etc., and exemplary
mass analyzers can include one or more collision cells, reaction cells or
other components as desired.
The detection device 2640 may be any suitable detection device that may be
used with existing mass
spectrometers, e.g., electron multipliers, Faraday cups, coated photographic
plates, scintillation
detectors, etc., and other suitable devices that will be selected by the
person of ordinary skill in the art,
given the benefit of this disclosure. The processing device 2650 typically
includes a microprocessor
and/or computer and suitable software for analysis of samples introduced into
MS device 2600. One or
more databases may be accessed by the processing device 2650 for determination
of the chemical
identity of species introduced into MS device 2600. Other suitable additional
devices known in the art
may also be used with the MS device 2600 including, but not limited to,
autosamplers, such as AS-
90plus and AS-93p1us autosamplers commercially available from PerkinElmer
Health Sciences, Inc.
[00123] In certain embodiments, the mass analyzer 2630 of the MS device 2600
may take numerous
forms depending on the desired resolution and the nature of the introduced
sample. In certain
examples, the mass analyzer is a scanning mass analyzer, a magnetic sector
analyzer (e.g., for use in
single and double-focusing MS devices), a quadrupole mass analyzer, an ion
trap analyzer (e.g.,
cyclotrons, quadrupole ions traps), time-of-flight analyzers (e.g., matrix-
assisted laser desorbed
ionization time of flight analyzers), and other suitable mass analyzers that
may separate species with
different mass-to-charge ratio. In some examples, the MS devices disclosed
herein may be hyphenated
with one or more other analytical techniques. For example, MS devices may be
hyphenated with
devices for performing liquid chromatography, gas chromatography, capillary
electrophoresis, and
other suitable separation techniques. When coupling an MS device with a gas
chromatograph, it may
be desirable to include a suitable interface, e.g., traps, jet separators,
etc., to introduce sample into the
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MS device from the gas chromatograph. When coupling an MS device to a liquid
chromatograph, it
may also be desirable to include a suitable interface to account for the
differences in volume used in
liquid chromatography and mass spectroscopy. For example, split interfaces may
be used so that only a
small amount of sample exiting the liquid chromatograph may be introduced into
the MS device.
Sample exiting from the liquid chromatograph may also be deposited in suitable
wires, cups or
chambers for transport to the ionization devices of the MS device. In certain
examples, the liquid
chromatograph may include a thermospray configured to vaporize and aerosolize
sample as it passes
through a heated capillary tube. Other suitable devices for introducing liquid
samples from a liquid
chromatograph into a MS device will be readily selected by the person of
ordinary skill in the art,
given the benefit of this disclosure. In certain examples, MS devices can be
hyphenated with each other
for tandem mass spectroscopy analyses.
[00124] In certain embodiments, the systems and devices described herein may
include additional
components as desired. For example, it may be desirable to include a
photosensor in an optical path of
the plasma so the system can detect when the plasma has been ignited. It may
be desirable to switch
from the driven mode to the oscillation mode as soon as the presence of the
plasma is detected by the
photosensor. In certain examples, the components of the generators described
herein may be air
cooled, liquid cooled or cooled with thermoelectric devices such as Peltier
coolers. One or more fans
may be present where air cooling. A chiller or circulator may be present to
circulate a fluid through the
system to absorb heat from the electronic components.
[00125] In some examples, the generators described herein can be used in non-
instrumental
applications including, but not limited to, vapor deposition devices, ion
implantation devices, welding
torches, molecular beam epitaxy devices or other devices or systems that use
an atomization and/or
ionization source to provide a desired output, e.g., ions, atoms or heat, may
be used with the generators
described herein. In addition, the generators described herein can be used in
chemical reactors to
promote formation of certain species at high temperature. For example,
radioactive waste can be
processed using devices including the generators described herein.
[00126] In certain examples, the generators described herein may be used to
ignite a plasma in a
torch body by providing power to an induction device from the generator in a
driven mode, and switch
the generator from the driven mode to an oscillation mode once the plasma is
ignited. In some
instances, the generator may remain in the driven mode for some period to
power the induction device.
[00127] In certain embodiments, the generators described herein may be used in
quality control
application or in field service application to provide information regarding
various components of the
system. For example, a technician can use the generator as a means of
determining which
component(s) of the system may need replaced. In operation, torches and
induction devices can fail
from continued heat exposure, or electronic components may fail from
overheating, overuse or other
CA 03022428 2018-10-26
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reasons. In some instances, a control signal (or signal of known amplitude,
shape, waveform, etc.) can
be provided in the driven mode of the generator and used to determine if the
electronics of the
generator are the cause of poor performance of the system. If the control
signal detected represents an
anticipated control signal, then the electronics may be removed as a cause of
poor system performance.
If desired, the control signal may be sent remotely by a technician so the
technician can be provided
remote feedback as to which of the components of the system may need
replacing. For example, the
control signal can be used to provide the technician information about the
fidelity of the electronics, so
they can take the desired components with them on a service call to repair the
system.
[00128] In certain configurations, even though the hybrid generators described
herein may be
operated in a driven mode, an oscillation mode and a hybrid mode, an end user
may operate the
generator in only one of these modes. For example, the user may disable the
driven mode and operate
the generator exclusively in the oscillating mode. Similarly, the user may
operate the generator
exclusively in the driven mode or the hybrid mode if desired. Switching
between the modes is not
required for proper operation of an inductively coupled plasma or other
suitable atomization/ionization
device sustained using the hybrid generator, though depending on the
conditions used switching
between modes can provide better performance.
[00129] In certain instances, the generators described herein can be used to
provide RF power to
drive an induction device, e.g., load coil or other induction device, at one
end. For example, a single-
ended transistor, e.g., power transistor in the same phase, can be used to
drive a load coil at one end of
the load coil and the other end of the load coil may be grounded. Where two or
more induction devices
are present, one may be driven differentially by a pair of transistors in
opposite polarities, e.g., out of
phase, and the other may be driven by a power transistor to drive the load
coil at one end. Any of the
various induction devices and configurations described herein may use the
single-ended design where
the load coil is driven at one end by the generator.
[00130] In certain configurations, it may be desirable to operate the
generator in an oscillation mode
without switching to the driven mode. In some instances, this oscillation
operation can be performed
by disabling the driven mode circuit components as noted herein. In other
configurations, the
generator itself may comprise only the oscillation circuit components, e.g.,
the driven mode circuitry
can be omitted entirely from the generator. For example, the driven mode
circuits in various
schematics described herein can be omitted entirely so that the circuit used
in the oscillation only mode
is configured without any driven mode circuitry. Without wishing to be bound
by any particular
theory, power transistors in a generator circuit can be near the breakdown
limit because their output
power is near their maximum rated power. A voltage spike at the input of
transistors may damage the
transistors themselves. In the oscillation design, the feedback is derived
directly from the plasma load
coil terminals (e.g., see between 260 and 232, and between 260 and 234 of FIG.
2B via feedback
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capacitors 242 and 244). This configuration enables fast adjustment in the
frequency for optimal
impedance matching, e.g., within about three RF cycles, which is an advantage
when the plasma load
resonant frequency, is subject to change by the liquid sample (sample could
have soil, solids, harsh
mixture of elements, etc.). The plasma load coil terminals have voltage
fluctuation and frequency
instability (high phase noise) because it is load sample dependent. With a
positive feedback in an
oscillator, the voltage fluctuation derived from the plasma output terminals
may escalate to destructive
voltage spikes. The feedback signals from capacitors 242 and 244, if fed to
the power transistors 222
and 224 without protection, may damage the devices 222 and 224 operating near
the breakdown limit.
[00131] To limit damage to the transistors, several possible oscillation
circuits or circuit
configurations can be used. Referring to FIG. 36, which shows an oscillation
only circuit 3600 (e.g.,
one without any driven mode circuit), the frequency provided to the load coil
3660 is scanned and
tuned to a frequency which permits successful plasma ignition, e.g., a
frequency which may maximize
the coil voltage if desired. Alternatively, a fixed, lower supply voltage VDD
(e.g., 9 V) can be selected
for a larger transistor drain capacitance to lower the frequency during
ignition in the oscillation only
mode of operation. A detector 3670, which is electrically coupled to a
processor 3680 through signal
converters 3682, 3684, may be used to monitor the plasma. For example, the
detector 3670 may be
configured as an RF detector that can be used to monitor RF signals provided
to the load coil 3660. In
other configurations, the detector 3670 may be configured as an optical
detector, e.g., a light sensor,
fiber optic sensor or other device, that can receive light emissions from the
plasma once the plasma is
ignited. In some embodiments, the detector 3670 may be omitted and the power
levels for a particular
load coil (or other induction device) may be fixed and be set at a level to
avoid transistor breakdown.
In operation, the determined power level is provided to the load coil 3660,
which surrounds some
portion of a torch body (not shown), and plasma gas provided to the torch body
is ignited while the
power is being applied. A plasma is generated and sustained by continued
application of RF power
from the load coil 3660. During sample introduction, sample is typically
sprayed or nebulized into the
plasma along with a carrier such as a solvent. The plasma is operative to
desolvate the sample and
atomize and/or ionize the chemical species in the plasma.
[00132] The power gain of drivers 3652, 3654 can reduce the required amplitude
of the feedback
signal (i.e., smaller) at the input of drivers 3652, 3654. Without drivers
3652, 3654, a larger feedback
signal may be required to drive the power devices 3622, 3624. By selecting
devices 3652 and 3654
which have similar input breakdown limit as the power transistors 3622 and
3624, the higher voltage
spikes in the already reduced feedback signal are less likely to damage 3652
and 3654. For example,
power devices 3622 and 3624 can be selected to comprise a gate breakdown limit
from +6V to -11V.
The protection devices 3652 and 3654 can also be selected to comprise the same
gate breakdown limit
(+6V to -11 V), but the input feedback signal is now smaller. By selecting or
matching the breakdown
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limits of the devices 3622, 3624, 3652 and 3654, there is reduced risk that
the power transistors 3622,
3624 are damaged due to overly high input power. If desired, to further
protect against fast, transient
spikes, the devices 3652 and 3654, despite their smaller rated output power,
can be selected to have a
high output breakdown limit (e.g., similar to the power transistors 3622 and
3624, rated to DC power
supply VDD=50V operation at a maximum breakdown limit of 110V). However, the
VDD supply of
3652 and 3654 are reduced in actual operation (e.g., rated to 50V operation,
but use VDD=15V in
practice), so that the fast, transient voltage spikes at the feedback signal
are clipped off at the output of
drivers 3652, 3654 by the much reduced voltage supply rail and will not over-
drive power transistors
3622, 3624. Also, drivers 3652, 3654 will not suffer from output breakdown
because of the large
margin in VDD (e.g. 15V operation for a 50V capable device).
[00133] In other configurations where the generator is an oscillation mode
only generator, the
generator may comprise suitable circuitry to provide harmonic emission
control. Modern power
transistors often have substantial power gain at high frequencies (e.g.,
hundreds of MHz), where the
fundamental plasma frequency is typically at a low frequency (e.g.., tens of
MHz). It may be desirable
to include one or more low pass filters to eliminate RF emission at the high
hannonics (multiples of RF
frequencies). In a high power oscillator (kilo-watt power), the feedback
signal is often at a moderately
large power, ranging from 5 Watt to 100 Watts. As a result, a low-pass filter
can be used to filter the
feedback signal to suppress high harmonics at the input of the power
transistors. For example and
referring to FIG. 37, low-pass filters 3657, 3659 can be used to filter the
feedback signal to suppress
high harmonics at the input of the power transistors 3622 and 3624,
respectively. Due to the large
feedback signal, bulky passive components with high power ratings may be
needed. The large physical
size is a penalty to the required component space and efficiency. By inserting
drivers 3652 and 3654,
the feedback signal amplifier is reduced so that small, surface mount passive
components (e.g., 1206
package) can be used to make an efficient, high-order low pass filter to
effectively cut-off the emission
at the harmonic frequencies. This configuration protects the power transistors
3622, 3624 while
permitting oscillation mode operation.
[00134] One illustration of a suitable circuit for harmonic emission control
is shown in FIG. 38.
The L-R-C components R9, C11, R3, C8, L10 (shown in the dotted box labelled
3810) form a high-
order low-pass filter to suppress the harmonics. All these components can be
small surface mount
components (e.g., 1206 packages). LIO can also be replaced with a small 1206
package high-order
ceramic low-pass filter, which offers 20dB cut off at 200MHz or higher
frequencies.
[00135] In some instances, the feedback of the oscillator can be designed or
selected such that the
open loop gain > 1, close loop gain = 1, and the phase shift is zero or an
integer multiple of 360
degrees. (i.e., no change to the signal phase). The feedback oscillator can be
designed to oscillate at
one main frequency with good stability. In practice, the oscillator can run at
any frequency, or
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frequencies, or with a lot of frequency fluctuation (high phase noise), as
long as it satisfies the phase
shift criteria noted above. In the designs described herein, the phase-shift
of the feedback loop is
contributed by both the plasma load coil and also the low-pass filter phase
shift. As a result, the free-
running frequency of the oscillator is determined partially (i.e., not
entirely) by the plasma sample load
and partially by the low-pass filter. The fixed phase shift of the low-pass
filter made of stable passive
R-L-C components desensitizes the sample load dependent phase-shift of the
plasma at a high phase
noise. Effectively, it can reduce the phase noise of the plasma oscillator and
can improve its stability.
[00136] In certain instances, it may be desirable to provide for fine
frequency control to permit
adjustment of the generator frequency instead of using a free-running
oscillator. For example, during
plasma ignition, when the plasma load coil is known to oscillate at a lower
frequency (prior to a lighted
plasma), the oscillator can be selectively adjusted to a lower frequency. The
output parasitic
capacitance of the devices 3652 and 3654, which are typically MOSFET or LDMOS
devices, are
voltage dependent (i.e., capacitance varies with the VDD DC supply voltage, or
VDS, the drain-source
voltage). The output capacitance of a typical device suitable for use as
drivers 3652, 3654 is shown in
the plot of HO. 39, marked by label "COSS". Since VDD in these devices is only
for protection, a
lower or higher VDD provided to these devices is not so important as long as
it provides a sufficient
limit to clip off the output voltage transient. Therefore, the VDD can be
adjusted to fine tune the
frequency (e.g., lower VDD to 9V to obtain a high capacitance for a lower
oscillation frequency at
plasma ignition, and use a higher VDD=13V after the plasma is lighted). This
frequency adjustment
permits both lighting of the plasma and running the plasma in an oscillation
only mode, e.g., without
the need to use a driven mode or to use a generator circuit including any
driven mode circuitry.
[00137] In certain configurations and referring again to FIG. 37, to maximize
the neutral voltage
potential, and to maximize the transistor lifetime, the pair of feedback
signals from the plasma load coil
3660 may have different voltage amplitudes due to the power from driver
amplifiers 3652, 3654 and
can be divided evenly between the push-pull power transistors 3622, 3624. In
contrast, if one
transistor (e.g., 3622) is driven with a larger input signal than the other
transistor (e.g., 3624), the
transistor 3622 will conduct more current than 3624, and its lifetime will be
reduced. It may be
desirable to evenly distribute the feedback signal power to the push-pull
transistors 3622, 3624 so their
lifetimes are about the same. Such even distribution can be accomplished in
numerous manners. For
example, to ensure that the feedback signal power from the driver amplifiers
3652 and 3654 is divided
evenly between power transistors 3622 and 3624, the feedback signals can be
cross-coupled such that
the feedback derived from the power transistor 3622 will eventually drive
3624, and the feedback
signal derived from the power transistor 3624 will eventually drive 3622.
Driver amplifiers 3652 and
3654 drive the primary coil of a transformer (not shown) in a push pull
fashion. The secondary coil of
the transformer drives the power transistor 3622 and 3624. The center-tap of
the secondary coil can be
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grounded as an option. If desired, a negative feedback resistor can be used to
lower the output
impedance of the amplifiers 3652 and 3654. A feedback resistor (from the
output to the input) will
lower the output impedance of the amplifier at the expense of some gain
reduction. A lower device
gain (due to the addition of the negative feedback resistors) is not important
if these devices have high
open-loop gain as the closed-loop gain should still be large enough for
oscillation. If the feedback
signal pair from the output of driver 3652 or 3654 is unequal, this circuit
scheme will reduce the power
unbalance substantially, so as to drive the power transistor 3622 and 3624
with substantially equal
power. In the extreme unbalanced case when there is no voltage on one of the
feedback signals (e.g.,
3652), but a strong feedback signal on the other side (e.g., 3654) the low
impedance of the driver
amplifier 3652 output will resemble a low-impedance ground. The driver 3654
that provides a strong
output feedback will drive the primary coil of the transformer on one side,
and the other side of the
primary coil terminated by a low-impedance ground at 3652. The overall current
in the primary coil
will generate a magnetic flux which will be shared by the secondary coil, and
drives the power
transistors 3622, 3624 evenly.
[00138] One circuit configuration for balancing the input power to the power
devices is shown in
FIG. 40. The circuit 4000 comprises amplifiers 4022, 4024, respectively, and a
load coil 4060 coupled
to the amplifiers 4022, 4024 through capacitors 4032, 4034, respectively.
Additional components, e.g.,
resistors, amplifiers, etc. may also be present but are not shown to simplify
this illustration. The
frequency provided to the load coil 4060 can be scanned and tuned to a
frequency which permits
successful plasma ignition, e.g., a frequency which may maximize the coil
voltage if desired.
Alternatively, a fixed, lower VDD (e.g., 9 V) can be selected for a larger
transistor drain capacitance to
lower the frequency during ignition for the oscillation only mode of
operation. A detector 4070, which
is electrically coupled to a processor 4080 through signal converters 4082,
4084, may be used to
monitor the plasma. For example, the detector 4070 may be configured as an RF
detector that can be
used to monitor RF signals provided to the load coil 4060. In other
configurations, the detector 4070
may be configured as an optical detector, e.g., a light sensor, fiber optic
sensor or other device, that can
receive light emissions from the plasma once the plasma is ignited. In some
embodiments, the detector
4070 may be omitted and the power levels for a particular load coil (or other
induction device) may be
fixed and be set at a level to avoid transistor breakdown. DC block capacitors
4053, 4055 may be
present to isolate the output VDD voltage from the gate input bias voltage.
The DC block capacitors
4053, 4055 can be electrically coupled to the load coil 4060 through
capacitors 4042, 4044,
respectively. The DC block capacitors 4053, 4055 can also be electrically
coupled to the load coil
4060 through the low-pass filters 4057, 4059, respectively. The drivers 4052
and 4054 are
implemented with transistors, where the transistor output is inverted from the
transistor input (e.g.,
about a 180 degrees phase shift). Resistors 4092, 4094 may be electrically
coupled between the input
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and output of the drivers 4052, 4054, respectively, to lower their output
impedances by negative
feedback, and together with the transformer 4099, to balance the input power
in the power transistors
4022, 4024. As noted herein, this balancing can maximize the neutral voltage
potential and increase
transistor lifetime. Many types of transformers can be used including ferrite
core transformers, for
example.
[00139] In certain configurations, the output power of the power transistor is
typically a product of
DC supply voltage (VDD) and DC drain current (ID) multiplied by the
efficiency. The same amount
of output power can be generated by a combination of a higher voltage and a
lower current or a lower
voltage and a higher current. An excessively high voltage can cause transistor
breakdown failure, and
an overly high current can cause transistor meltdown failure. In certain
instances, the voltage and
current of the power devices can be independently adjustable to maximize the
safety margin from
voltage breakdown or current meltdown. While not required, it may be simpler
to change the voltage
rather than changing the current as current is dependent on the variable
plasma impedance which is
dependent on the sample, the input power to the power devices, and the device
bias voltage (e.g., gate
bias voltage at the input). In the circuits described herein, the bias current
and voltage of the driver
devices can each be adjusted to increase or decrease the feedback signal
amplitude (i.e., input power to
the power devices). As a result, by controlling both the voltage and currents
of the power transistors in
the RF generator desirable attributes can be achieved including, but not
limited to, controlling voltage
and currents to operate optimally and/or to compensate for over-voltage or
over-current operation due
to the changes of the plasma impedance. In many configurations, the driver
devices are operating at a
much smaller signal level compared to the power devices, so changing the
current and voltage of the
driver devices will not typically affect the overall efficiency of the plasma
generator, which can be as
high as 75% or more.
[00140] Certain specific examples are described below to illustrate further
some of the novel
aspects, embodiments and features described herein.
[00141] Example 1
[00142] A circuit was constructed as shown in FIG. 27 to test driven and
oscillation modes. The
circuit 2700 includes a signal source 2710, e.g., a frequency synthesizer, a
VCO, a phase locked loop, a
numeric control oscillator (NCO), or an NCO that is part of a phase locked
loop. The source 2710 is
electrically coupled to a pair of amplifiers 2712, 2714. The amplifiers 2712,
2714 are each electrically
coupled to another set of power amplifiers 2722, 2724, respectively, and a
load coil 2760 through
capacitors 2732, 2734, respectively. The power amplifiers 2722, 2744 were
designed with sufficient
RF output power for generating/sustaining the plasma. Control signals were
present between the
processor 2780 and the amplifiers 2722, 2724. The frequency provided to the
load coil 2760 from the
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frequency synthesizer 2710 was scanned and tuned to a frequency which
maximized the coil voltage.
A RF detector 2770, which is electrically coupled to a processor 2780 through
signal converters 2782,
2784, may be used to monitor the RF signals provided to the load coil 2760. As
noted herein, the RF
detector 2770 may be replaced with a photosensor to monitor plasma ignition.
The plasma was ignited
by enabling the signal source 2710 and the amplifiers 2712, 2714, 2722 and
2724 to power the coil
2760 in a driven mode. The RF detector 2770 was used to monitor the plasma. A
microcontroller
2780 (MCU ARM Cortex-M3) was used to receive signals from the RF detector
through an analog-to-
digital converter 2784 and to send control signals to the amplifiers 2712,
2712, 2722 and 2744 through
a digital-to-analog converter 2782.
[00143] After the plasma was ignited and a desired voltage level is detected
using the RF detector
2770, the generator was switched from the driven mode to the oscillation mode
as shown in FIG. 28.
The processor 2780 disabled the amplifiers 2712, 2714 and enabled the feedback
amplifiers 2782. 2784
to switch from the driven mode to the oscillation mode. At some period (in a
hybrid mode), all of the
amplifiers were enabled during transition from the driven mode to the
oscillation mode. Once in the
oscillation mode, the impedance of the circuit may be adjusted rapidly to
match impedance changes in
the plasma, which becomes parts of the circuit, as sample and solvent is
introduced into the plasma.
[00144] Example 2
[00145] The generator of Example 1 was used in combination with a single
quadrupole mass filter
spectrometer to measure the peak shapes of various elements. A copper load
coil from a NexION
instrument was used as the induction device. The other components of the
NexION system were also
used to perform the measurements. A frequency of 40 MHz was used.
[00146] FIG. 29 shows a spectrum for lithium and beryllium obtained using the
generator and the
mass spectrometer using lithium and beryllium standards.
[00147] FIG. 30 shows a spectrum for magnesium obtained using the generator
and the mass
spectrometer using a magnesium standard.
[00148] FIG. 31 shows a spectrum for indium obtained using the generator and
the mass
spectrometer using a indium standard.
[00149] FIG. 32 shows a spectrum for uranium-238 obtained using the generator
and the mass
spectrometer using a U-238 standard.
[00150] FIG. 33 includes a table comparing the measurements of the elements
using the standard
NexION instrument to those of the hybrid generator in a driven mode and in an
oscillation mode. The
oscillation measurements using the hybrid generator are similar to or better
than those obtained with
the NexION generator. For certain elements (Be, Mg), the driven mode using the
hybrid generator
provided better results than the oscillation mode.
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[00151] Example 3
[00152] The hybrid generator was imbalanced to test its stability. The null
point (virtual ground
was electronically moved along the load coil by unbalancing the driven
differential signal amplitude
and phase at 34.44 MHz using the processor. Phase balance can affect
sensitivity, including the oxide
ratio, and amplitude balance can also affect sensitivity. The various phases
used at different times are
shown in FIG. 34.
[00153] The best signal was observed when the generator was differentially
driven (0, 180 degrees)
with a phase mirror within about 5 degrees (see top two curves in FIG. 34,
which represent the Ce
signal (top curve) and the In signal (curve below top curve)). A phase error
of about 20 degrees
increased the oxide ratio substantially (see Ce0 curve toward the bottom of
the chart above the x-axis).
[00154] Example 4
[00155] The measurements performed in Example 2 were repeated using slightly
different
frequencies. The results are shown in the table of FIG. 35. The oscillation
mode of the hybrid
generator provides results similar to those of the standard NexION generator.
The slight increase in
frequency used (35.96 MHz) in the oscillation mode compared to that frequency
(34.7 MHz) used to
obtain the measurements of FIG. 33 results in the oscillation mode providing
better results than the
driven mode for all elements measured.
[00156] Example 5
[00157] A generator comprising an oscillation circuit as shown in FIGS. 37 and
38 was tested. The
generator did not include a driven mode or any driven mode circuitry. Power
transistors capable of 1
Kw power output at 230 MHz were used. As shown in FIG. 41, the emission of a
34 MHz plasma
generator at the harmonics (multiples of 34 MHz) is relatively clean across a
wide spectrum up to 1
GHz.
[00158] Example 6
[00159] The generator of Example 5 was tested to verify its ability to balance
the power. One of
the feedback signals was removed entirely by removing capacitor 3642 from the
circuit. Both power
transistors 3622, 3624 were still driven due to the power balancing, and the
plasma could still be
sustained. The circuit can provide for excellent power matching typically to
within about 4% current
difference.
[00160] When introducing elements of the examples disclosed herein, the
articles "a," "an," "the"
and "said" are intended to mean that there are one or more of the elements.
The terms "comprising,"
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"including" and "having" are intended to be open-ended and mean that there may
be additional
elements other than the listed elements. It will be recognized by the person
of ordinary skill in the art,
given the benefit of this disclosure, that various components of the examples
can be interchanged or
substituted with various components in other examples.
[00161] Although certain aspects, examples and embodiments have been described
above, it will be
recognized by the person of ordinary skill in the art, given the benefit of
this disclosure, that additions,
substitutions, modifications, and alterations of the disclosed illustrative
aspects, examples and
embodiments are possible.
54
