METHOD OF ACTIVATING CASCADED ELECTRON TUBES

PROCEDE D'ACTIVATION DE TUBES ELECTRONIQUES EN CASCADE

English Abstract

Disclosed is a method of activating a plurality of cascaded electron tube
stages within a common vacuum enclosure. Beneficially, energy supplied to the
first
stage serially propagates through any intervening stage to the final stage so
as to
facilitate activation of all tube stages.

French Abstract

Un procédé est révélé relativement à lactivation dune pluralité détages de tubes électroniques en cascade à lintérieur dune enceinte commune sous vide. Avantageusement, lénergie fournie au premier étage se propage de manière sérielle dans tout étage intermédiaire jusquà létage final de sorte à faciliter lactivation de tous les étages de tube.

Claims

What is claimed is:
1. A method of activating a plurality of cascaded electron tube stages within
a
common vacuum enclosure, the method comprising:
a) interconnecting the plurality of cascaded electron tube stages in series,
from a non-final stage to a final stage, in such a manner that in each non-
final stage an electrode is connected to an electrode of a subsequent
stage by a respective electrical interconnection line;
b) at least one of said respective electrical connection line comprising a
linking structure for electrically and mechanically joining an electrode of a
previous stage with an electrode of a subsequent stage;
c) placing the plurality of cascaded electron tube stages within the vacuum
enclosure and exhausting air from the enclosure; and
d) providing electrical voltage between cathode and anode of a first serially-
connected stage so as to supply electrical energy to the first stage; said
energy serially propagating through any intervening stage to the final
stage so as to facilitate activation of all tube stages.
2. The method of claim 1, wherein said electrical voltage between the cathode
and
the anode of the first serially-connected stage causes activation of all
stages.
3. The method of claim 1, wherein the entire length of each linking structure
forms
an electrical transmission line.
4. The method of claim 1, wherein said electron tube is a cold cathode field
emission electron tube.
5. The method of claim 1, wherein the electrical interconnection line
comprises an
electrical transmission line.
6. The method of claim 1, wherein the plurality of cascaded electron tube
stages is
three in number.
7. The method of claim 1, wherein the plurality of cascaded electron tube
stages is
four in number.
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Description

CA 02861715 2014-08-28
METHOD OF ACTIVATING CASCADED ELECTRON TUBES
[0001]
FIELD OF THE INVENTION
[0002] The invention relates to a method of activating a plurality of electron
tube stages
with a cascaded structure in a common vacuum enclosure.
BACKGROUND OF THE INVENTION
[0003] Activation of electron tubes is the process by which the cathode is
converted from
its as-manufactured state into a functioning electron emitter. Typically, this
process
involves drawing current from the cathode through the anode, while the tube is
still
connected to a vacuum pumping system. Specific implementation varies with the
type of
cathode used. Activation requires supplying operating voltages equal to or
greater than
those normally encountered in operation of the tube. Activation takes place
while the tube
is still connected to an external vacuum pump system. This is done to
facilitate the
removal of impurities released from the cathode by the activation process. In
the case of
very high voltage tubes, the cost of suitable power supplies is very high. It
would,
therefore, be desirable to minimize the cost of high voltage power supplies
and to simplify
and expedite the manufacturing process.
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CA 02861715 2014-08-28
BRIEF SUMMARY OF THE INVENTION
[0004] The invention provides a method of activating a plurality of cascaded
electron tube
stages within a common vacuum enclosure. The method comprises interconnecting
the
plurality of cascaded electron tube stages in series, from a non-final stage
to a final stage,
in such a manner that in each non-final stage an electrode is connected to an
electrode of
a subsequent stage by a respective electrical interconnection line. At least
one of said
respective electrical connection line comprises a linking structure for
electrically and
mechanically joining an electrode of a previous stage with an electrode of a
subsequent
stage. The plurality of cascaded electron tube stages is placed within the
vacuum
enclosure and air is exhausted from the enclosure. An electrical voltage is
provided
between cathode and anode of a first serially-connected stage so as to supply
electrical
energy to the first stage. A sufficient amount of said energy serially
propagates through
any intervening stage to the final stage so as to facilitate activation of all
tube stages.
[0005] The foregoing method avoids the drawbacks of the prior art method of
activating
individual tubes mentioned above. This is accomplished by using, in a
preferred form,
only a single power supply to activate all the stages cascaded electron tube
stages nearly
simultaneously. The power supply needs to only meet the voltage requirement of
the first
stage tube, since the increased voltage required for each succeeding stage is
provided by
the voltage gain of the preceding stage. This avoids the need for larger and
more costly
power supplies for the succeeding stages, and for larger and substantially
more complex
exhaust stations involving, for instance, the use of larger feedthroughs that
then require a
larger vacuum enclosure and increased vacuum pumping and heating requirements.
BRIEF DESCRIPTION OF DRAWINGS
[0006] In the drawings, in which like reference numerals refer to like parts:
[0007] FIG. 1 is a simplified perspective view, partially cut away, of key
parts of integrated,
three-stage, cascaded electron tubes, with various parts omitted for clarity;
[0008] FIG. 2 is a block diagram view of a scheme for activating integrated
cascaded
electron tubes; and
[0009] FIG. 3 is a block diagram view of a variable number of stages of
cascades electron
tubes in accordance with the invention.
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DETAILED DESCRIPTION OF THE INVENTION
Inventive Method of Activating Cascaded Electron Tubes
[0010] Activation of an electron tube is the penultimate process step in the
manufacture of
the tube, just prior to pinching off the exhaust tubulation. The purpose of
activation is to
convert the as-manufactured cathode into a functioning electron emission
element.
Typically, this process involves drawing current from the cathode through the
anode, while
the tube is still connected to a vacuum pumping system. Specific
implementation varies
with the type of cathode used. It is important to recognize that the
activation process is
completely independent of the electrode geometry of the tube or tube stage.
[0011] The present method of activating applies to the integrally series-
connected
electron tubes as described in connection with FIG. 1. Activation of a
thermionic cathode
primarily changes the chemistry of the emitting surface of the cathode, while
activation of
a cold cathode is used to remove impurities from the cathode.
[0012] FIG. 1 shows key parts of cascaded electron tubes 10 in accordance with
an
aspect of the invention. In FIG. 1, a vacuum enclosure 12 of nickel alloy, for
instance,
encloses non-final stages 14 and 16 and final stage 18 of cascaded electron
tubes 10.
Cascaded electron tubes 10 include first stage cathode input 19a, and last
stage anode
output 19c.
[0013] Non-final stage 16 includes an anode 16a, a grid 16b and a cathode 16c.
A non-
final linking structure 22 supports the anode 16a of non-final stage 16, as
well as supports
the cathode 18c of subsequent stage 18. The linking structure 22 generally has
the form
of a two-tined fork on one end, with tines 22a and 22b, a cathode support 22c,
and an
insulator 28. At one axial end of the linking structure 22 (along the axis of
cathode 16c),
linking structure 22 is connected to the anode 16a. The right-hand end of
linking structure
22 terminates in a cathode support 22c for final stage 18.
[0014] FIG. 1 omits various elements for clarity, for instance, showing only
grid
feedthrough 32b. Further omitted for clarity from FIG. 1 are dielectric
support elements for
accurate positioning and supporting the various internal tube elements.
Inclusion of such
support elements will be routine to those of ordinary skill in the art.
[0015] The foregoing description of FIG. 1 has focused on the second non-final
stage 16.
The first stage 14 and the final stage 18 share much in common with the second
stage 16,
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with some major differences as follows. Unlike the second stage 16, the first
stage 14 has
its cathode supported from a first stage cathode input 19a, rather than from a
linking
structure (e.g., akin to 20) from a prior stage. The final stage includes a
linking structure
24 that terminates in a last stage anode output 19c, rather than a cathode
support
structure (e.g., 22c of second stage 16) for a following stage. The final
stage 18 is
electrically insulated from vacuum enclosure 12 by dielectric insulator 13.
Finally, it
should be noted that in this specification like reference numerals refer to
like parts, so that,
for instance, the foregoing description of anode 16a for second stage 16
applies as well to
reference numeral 14a for first stage 14 and to 18a of third stage 18.
[0016] An aspect of the invention is the use of a single power supply to
activate the
successive stages 14, 16 and 18 (FIG. 1), as opposed to using three discrete
power
supplies of progressively increasing voltages. Since the cost of power high
voltage power
supplies increases rapidly with increasing output voltage rating, the ability
to activate a
very high voltage stage with a relatively low voltage power supply is
desirable. This is
achieved by taking advantage of the inherent amplification provided by each
stage (14, 16
and 18). The first stage 14 raises the voltage to the correct level to
properly activate the
second stage 16; the same process is repeated for each successive stage. In
the final
stage (e.g., 18 or higher), the amplification process is still required but is
used internally to
activate that stage.
[0017] FIG. 2 shows a scheme 50 for activating integrated cascaded electron
tubes 52,
shown in dashed lines within a vacuum enclosure 51, which may suitably
comprise the
cascaded electron tubes described above in connection with FIG. 1. A variable
high
voltage power supply 54 feeds the input terminal 42 of amplifier 52. A load
resistor 56 is
connected to output terminal 44 on one end, and to a shunt resistor 58 on the
other end.
The other side of shunt resistor 58 is connected to common ground 60. The
center
conductor of a coaxial jack 62 is connected to the common terminal of load
resistor 56
and shunt resistor 58. The ground connection of coaxial jack 62 is connected
to the shunt
resistor ground connection 64. An exhaust means 66, shown diagrammatically, is
used to
exhaust air and impurities from vacuum enclosure 51.
[0018] To activate the cascaded electron tubes 52, air is exhausted from
enclosure 51 by
exhaust means 66. Electrical voltage from variable high voltage power
supply 54 is
applied between the anode and cathode of the first serially connected serially
connected
tube stage within cascaded electron tubes 52. A sufficient amount of the
energy from
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power supply 54 is serially propagated through any intervening stage (here,
the second
stage) to the final stage so as to facilitate activation of all stages.
Preferably, the energy
supplied by the power supply 54 to the anode and cathode of the first stage is
sufficient to
cause activation of all stages. Beneficially, each stage amplifies the input
activation
voltage to the correct value for the level of activation mentioned in the
preceding two
sentences by virtue of its design.
[0019] Although FIG. 2 and, by implication, FIG. 1, show three stages of
cascaded
electron tubes), four or more stages can be incorporated into cascaded
electron tubes.
Thus, FIG. 3 diagrammatically shows, between input 42 and output 44, stages
70a, 70b,
70c and intervening, unnumbered stages, represented by a line break, until
stage 70n.
These four or more stages can replace the three stages of FIGS. 1 and 2.
The
interrelation of the various stages of FIG. 3 can be discerned from the
interrelation of
successive stages in FIG. 1. In particular, stage 70a (FIG. 3) corresponds to
first stage 14
(FIG. 1), stages 70b, 70c and any further intervening stages in FIG. 3
correspond to
second stage 16 in FIG. 3, and final stage 70n of FIG. 3 corresponding to
final stage 18 in
FIG. 1.
[0020] The scope of the claims should be not be limited by the preferred
embodiments
and examples, but should be given the broadest interpretation consistent with
the
description as a whole.
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Representative Drawing