Note: Descriptions are shown in the official language in which they were submitted.
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Emission spectroscopic analyzer
This invention relates to an emission spectroscopic
analyzer. More particularly, it relates to an emission
spectroscopic analyzer comprising means for exciting
a material to be analyzed to emit light and means for
detecting the emitted light in which the emitted light
is transmitted from the exciting means to the detecting
means through light-transmitting means.
Analysis of high-level radioactive materials in an
atomic energy related field i5 accompanied by remote-
controlled analysis with the use of a hot cell. Conven-
tional titrimetric or colorimetric analysis is designed
to be employed in a laboratory and is difficult to apply
to analysis in a hot cell. Further, these analytical
methods have certain disadvantages, e.g. their procedures
are complicated, and only a small number of materials can
be analyzed by them.
On the other hand, emission spectroscopic analysis, in
which a material to be analyzed is excited to emit light
and the wave length and intensity of the spectrum of the
emitted light are measured so as to determine the kinds
and contents of the component elements in the material,
can be employed for a wide range of concentrations of the
materials and can analyze several elements simultaneously.
Further, the procedure is not affected by the high-level
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radiation which the hot cell encounters. It is, however,
difficult to employ an emission spectroscopic analyzer in
a hot cell, since the high temperature and humidity and/or
the presence of acidic vapours reduce the accuracy of the
analysis and make maintenance of the analyzex extremely
difficult. It may be possible to separate the exciting
means from the detecting means and to locate the former in
the hot cell and the latter outside it. However/ this is
also difficult due to the attenuation of the transmitted
l~ght over a long transmitting path and the difficulty of
radiation shielding.
An emission spectroscopic analysis is also employed
in the iron industry, for example, for on-line analysis.
It is, however, undesirable to locate the analyzer under
harsh conditions, such as high temperatures and vibration,
which may be encountered in a factory, since accurate
analyses, namely accurate identification of the component
elements and quantitative analysis thereo~, are not then
achieved.
As a result of extensive study, it has now been found
that when a light-transmitting means is provided between
the exciting means and the detecting means of a emission
spectroscopic analyzer, the above described disadvantages
of the analyzer can be overcome.
According to the present invention, there is provided
an emission spectoscopic analyzer comprising: means for
exciting a material to be analyzed to emit light; means
for detecting the emitted light; light-transmitting means
provided between the exciting means and the detecting
means such that the emitted light impinging on a first
end of the light-transmitting means disposed at the
exciting means will be received at the detecting means
as light having been transmitted through the light-
transmitting means and emitted from a second end of
35 the light-transmitting means disposed at the detecting
means; a lens system attachable to the second end of the
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light-transmitting means to permit visual observation
of the emitted light therethrough; and a fine adjustment
device for adjusting the position of the first end of the
light-transmitting means in relation to the emitted light
from th~ material to be analyzed; wherein the light-
transmitting means is an image guide formed of a bundle
of a plurality of optical fibers in which the position of
each optical fiber in relation to other optical fibers at
one end of the image guide exactly corresponds to that
position of each optical fiber in relation to other op-
tical fibers at another end o the image guide, the bundle
of optical fibers being comprised of plural silica glass
fibers fused together to form a single unit, each silica
glass fiber having a core section of pure silica glass and
a cladding section surrounding the core section and made
of silica glass having a refractive index less than the
refractive index of the core section, and wherein the
second end of the light-transmitting means is detachably
mounted to the detecting means so that the lens system
may be attached to the detached second end of the light-
transmitting means for viewing of images transmitted
through the light-transmission means, whereby the optimum
position of the first end of the light-transmitting means
may be adjusted with the fine adjusting device to view a
desired image through the lens system and upon viewing of
the desired image the lens system may be detached and the
second end of the light-transmitting means may be attached
to the detecting means for detecting emitted light of the
desired image.
In the analyzer according to the present invention,
the exciting means may be any one that is used in
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conventional emission spectroscopic analyzers, for ex-
ample, a direct current arc (DCA), a high voltage spark
(HVS), a direct current plasma (DCP), an inductively
coupled plasma (ICP), etc. When the material to be
analyzed is a liquid, such as a solution of a material,
the preferred exciting means is a plasma of an inert gas
e.g. argon. When the sample is a solid, the preferred
exciting means is an electrical discharge e.g. an arc
discharge.
The light-transmitting means may be, fo~ example, an
image guide which comprises a bundle of optical fibers and
in which the position of each optical fiber in relation
to other optical fibers at one end of the guide exactly
corresponds to that at the other end of the guide so that
it can transmit light as an image; a light guide which
comprises a bundle of optical fibers and transmits the
intensity of the light; a single rod having a core of
large diameter; or a single optical fiberO Since the
light guide and the rod fiber transmit the intensity of
the light but not as an image, they cannot pick up the
normal position of the emitted light or the omitted light
from the material selectively. Namely, the light emitted
from the material and that emitted from the exciting means,
such as the plasma, simultaneously impinge on the end of
the optical fiber(s), so that the S/N ratio is reduced.
On the other hand, the image guide can catch the image of
the light in the normal position and transmit it. When a
narrow image angle lens system is provided on the end of
the image guide adjacent the exciting means, the position
of the end of the guide can be adjusted so as to select-
ively pick up the light emitted from the material to be
analyzed and not to pick up the light emitted from the
exciting means, which allows a precise analysis with a
high S/N ratio.
The image guide preferred in the present invention
comprises a bundle of a number of, for example, from about
1,000 to 150,000 optical fibers each having an outer
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diameter of feom 5 to 50 microns~ Each optical fiber
comprises a core which transmits the image of the light, a
cladding surrounding the core and having a smaller refrac-
tive index than the core and optionally a protective layer
S surrounding the cladding~ The optical fiber may be a
plastic fiber, a multiple components glass fiber, a silica
glass fiber, etc~ Of these, the silica glass fiber is
the most preferred, since it has better radiation and heat
resistance, lower transmission loss and better absorption
properties of ultraviolet light and shows stabilized
transmitting properties. The image guide may be flexible
in which the optical fibers are held together only at the
two ends, or slightly rigid in which the optical fibers
are fused together along their whole length. Generally,
the latter is preferred, since the guide has superior heat
resistance, mechanical strength and resistance to breakage
of each ~iber in use so that it can transmit a clearer
image than a completely flexible guide.
The detecting means may be of any conventional type
that can detect the emitted spectral lines. From the
detected spectral lines, the kinds and contents of
the component elements in the sample material can be
determined.
The present invention will be described, by way of
example, with reference to the accompanying drawings, in
which:
Fig. 1 is a schematic view of an emission spectro-
scopic analyzer according to one form of the invention;
Fig. 2 is a partial cross section of an image guide to
be used in the analyzer according to the invention; and
Figs. 3A to 3~ are calibration lines for boron,
silicon, molybdenum, palladium, aluminum, cerium, lithium
and potassium respectively.
In the analyzer shown in Fig. 1, a direct current
plasma-generating device 1 comprises a tungsten cathode
11, graphite-made anodes 12, 12 and a nozzle 13 for
supplying an atomized sample. Argon gas (Ar) is passed
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through no~zles along the electrodes 12, 12 as the
ionizable gas. As soon as the direct current arc is
generated between the cathode 11 and the anodes 12, 12,
the argon gas is ionized to form plasma (P). Then, the
sample to be analyzed is atomized by means of a ceramic
nebulizer (not shown), introduced into the argon plasma
and excited to emit light. The image of the emitted light
impinges on one end of an image guide 3 through a condenser
lens 2.
A partial cross section of an example of the image
guide is shown in Fig. 2. An optical fiber 21 comprises a
core 22 made of pure silica glass, a cladding 23 surround-
ing the core and a supporting layer 24 surrounding the
cladding. The cladding comprises silica glass doped with
a conventional dopant to lower the refractive index of
the pure silica glass. Thus, the refractive index of the
cladding may be adjusted by selecting the kind and amount
of the dopant. The supporting layer 24 comprises pure
silica glass and prevents damage and/or disruption of
the arrangement of the optical fibers when they are fused
together. The image guide shown in Fig. 2 may be produced
by inserting a number of optical fiber preforms, each
comprising the core, the cladding and the support layer,
in a silica glass tube, heating the tube containing the
optical fibers and drawing it to reduce the diameter and
to fuse the adjacent fibers together.
The position of the end of the image guide in relation
to the emitted light may be adjusted by means of a fine
adjustment de~ice 5. The end of the image guide is
detached from the spectrometer 4 (for example, GEW-170
manufactured by Shimadzu Corporation) and attached to a
lens system 7 which includes a color filter for visual
inspection. The optimum position of the end of the
image guide is visually determined through the filter by
adjusting the position of the end by the fine adjustment
device 5.
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After the optimum position of the end of the image
~uide is determined, the other end of the image guide
is detached from the lens system 7 and reattached to the
spectrometer 4. A colour filter 8 may be provided at the
end of the image guide near the detecting means.
The image transmitted through the image guide 3 is
emitted from the other end thereof and received ~y the
spectrometer 4. The kinds and the amounts of the com-
ponent elements in the sample can be determined from the
measured spectral lines and their intensity according to
the conventional procedure.
Examples of calibration lines for boron (2,496 A),
silicon (2,881 A), molybdenum (3,123 A), palladium
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(3,403 A), aluminum (3,961 A), cerium (4,186 A), lithium
(6,103 A), and potassium ~7,698 A) determined by the
analyzer shown in Fig. 1 are shown in Figs. 3A to 3H
respectively.
When the relation between the intensity of the
detected light described as above and the content of
various atoms is memorized by a computer, the kinds and
contents of the atoms contained in the material can be
easily calculated from the wavelength and the intensity
of the spectral lines observed by the analyzer.
Thus the invention permits emission spectroscopic
analysis to be carried out precisely and safely under
harsh conditions such as those encountered in a hot cell
or during on-line analysis in an iron works.
