Energy-dispersive-type semiconductor x-ray detector

Details Energy-dispersive-type semiconductor x-ray detector Energy-dispersive-type semiconductor x-ray detector

1998-05-08

2001-07-24

Epps, Georgia (Department: 2873)

Radiant energy

Invisible radiant energy responsive electric signalling

Semiconductor system

C250S352000

Reexamination Certificate

active

06265721

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an energy-dispersive-type semiconductor x-ray detector (hereinafter called the EDS detector) used for energy-dispersive-type element analyzers, for example, such as x-ray microanalyzers which are combined with an electron microscope and measure characteristic x-rays excited with an electron beam and emitted from a specimen, and fluorescence x-ray analyzers using x-ray excitation, and more particularly to an EDS detector in which a small-sized gas-circulation-type refrigerator is provided in a cryostat sliding in a given direction, helium gas is supplied through a connecting pipe to the refrigerator, and an x-ray detecting element is cooled by means of the refrigerator.
2. Description of Related Art
Although heretofore, as an EDS detector used for energy-dispersive-type element analyzers requiring a high resolution, lithium-drift-type silicon semiconductor x-ray detectors (silicon lithium detectors) have been widely used, the silicon (lithium) detectors have a problem in that when a drifted lithium ion moves into silicon due to thermal diffusion, the characteristics of the x-ray detecting element deteriorates, so that the element must be cooled by the use of liquid nitrogen at all times and liquid nitrogen replenished, thereby making daily maintenance troublesome.
On the other hand, as an alternative to the above-mentioned liquid nitrogen system, a small-sized gas-circulation-type refrigerator such as of a Joule-Thomson system and of pulse tube system has been developed. The small-sized gas-circulation-type refrigerator has a sufficient refrigerating capacity, has no mechanically driving part in the low-temperature generating section, and is simple in construction, so that the refrigerator is characterized by an extremely low vibration, a high reliability with respect to long-time operation, and an easy maintenance. There has been attempts to provide a small-sized gas-circulation-type refrigerator in a cryostat sliding in a given direction, to supply helium gas through a connecting pipe to the above-mentioned refrigerator, and to cool an x-ray detecting element by means of the above-mentioned refrigerator.
FIG. 4
shows schematically the configuration of a prior art EDS detector
40
, in which numeral
41
designates a cryostat configured so as to be slid on a guide base
42
in the arrow F or R direction. Provided in the cryostat
41
is a pulse tube refrigerator
43
, which includes a cold heat exchanger portion
43
b
and a refrigerator body
43
a
which is connected to a cold finger
44
extending in the horizontal direction. Provided on the head of the cold finger
44
is an x-ray detecting element
45
. Numeral
46
designates an x-ray window provided in front of the x-ray detecting element
45
.
The refrigerator body
43
a
of the above-mentioned pulse tube refrigerator
43
is connected through a connecting pipe
47
to a pressure converting valve unit
48
, which, in turn, is connected through a high-pressure helium piping
49
and a low-pressure helium piping
50
to a compressor
51
. Numeral
47
a
is a flexible pipe portion of the connecting pipe
47
connected to the refrigerator body
43
a.
In the EDS detector
40
having the above-mentioned configuration, the high-pressure and low-pressure helium gases adjusted by the compressor
51
are supplied to the pressure changeover valve unit
48
, and the pressure wave of the above-mentioned helium gas is supplied through the connecting pipe
47
to the refrigerator body
43
b
of the pulse tube refrigerator
43
, whereby the refrigerator body
43
a
is acceleratedly cooled, and due to the cold generated, the cold finger
44
is cooled and thus the x-ray detecting element
45
is cooled.
However, in this case, the above-mentioned connecting pipe
47
may vibrate due to the pressure wave of the helium gas therein, so that the vibration is transferred to the cryostat
41
housing the x-ray detecting element
45
, whereby the x-ray detecting element
45
may be vibrated or an electron microscope to which the EDS detector
40
is mounted may be vibrated, which can adversely affect the accuracy in measurement and in x-ray detection.
Accordingly, the prior art is still seeking improvements in this field.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention is made in view of the above-mentioned matters, and it is an object of the invention to provide an EDS detector in which even if connecting pipes may vibrate due to gas flow, such vibration will not be transferred to a cryostat side.
In order to achieve the above-mentioned object, the present invention provides an energy-dispersive-type semiconductor x-ray detector in which a small-sized gas-circulation-type refrigerator is provided in the cryostat sliding in a given direction, helium gas is supplied through the connecting pipes to the refrigerator, and an x-ray detecting element is cooled by means of the refrigerator, and in which of the above-mentioned connecting pipes, a connecting pipe body portion connected to a pressure converting value unit is allowed to contact a vibration-proofing stand and to be fixedly held therewith.
In the EDS detector of the present invention, the connecting pipe is fixed with the vibration-proofing stand mechanism to suppress the vibration of the connecting pipe. Accordingly, a phenomenon is eliminated wherein vibration is transferred to the cryostat housing an x-ray detecting element. Further, when a weight or weights are provided on a flexible portion at the head of the connecting pipe, the vibration of the connecting pipe can be more positively prevented.


REFERENCES:
patent: 5552608 (1996-09-01), Gallagher et al.
patent: 0277304 (1988-08-01), None
patent: 6109339 (1994-04-01), None

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