JP4332939B2 - Energy dispersive X-ray detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an energy dispersive X-ray detection device used in a fluorescent X-ray analyzer, an X-ray microanalyzer, and the like.
[0002]
[Prior art]
A fluorescent X-ray analyzer that measures the fluorescent X-rays emitted from a substance, knows the elements that make up the substance, and further performs a quantitative analysis to know the abundance of the elements, or similarly, the elements in the sample surface layer X-ray microanalyzer EPMA (Electron Probe Microanalyzer), scanning electron microscope SEM (Scanning Electron Microscope), etc. for performing qualitative and quantitative measurement of elements, two-dimensional analysis of element concentration, and state analysis A detection device is in use.
In the X-ray microanalyzer and the scanning electron microscope, as shown in FIG. 3, the thermoelectrons emitted from the tip of the filament in the electron gun 22 are converged and irradiated on the surface of the sample 24. In the X-ray fluorescence analyzer, When a high voltage is applied between the anti-cathode material and the filament in the X-ray tube, the surface of the sample is irradiated with X-rays emitted from the counter-cathode material when the thermoelectrons emitted from the filament collide with the anti-cathode material. To do.
When an electron beam or X-ray accelerated at such a high voltage irradiates the sample surface, the inner shell electrons of the atoms of the sample substance element are excited by the energy of the incident electrons or X-rays and are ejected out of the shell. The At this time, electrons in the outer shell fall, and energy corresponding to the energy difference between the electrons in the outer shell and the inner shell is emitted as characteristic X-rays. Since this value has an element-specific value, the emitted X-ray also has a specific wavelength or energy, which is called a characteristic X-ray.
Therefore, by measuring the wavelength or energy of the characteristic X-rays and their intensities, the elements of the sample surface material can be qualitatively / quantified.
[0003]
In these analyzers, an energy dispersive X-ray detector using a semiconductor detector 13 is used to measure characteristic X-rays.
A lithium drift type is generally used for the semiconductor detector 13. However, in order to improve detection performance, the semiconductor detector 13 is connected to the dewar 21 via the cold finger 12 using the dewar 21 containing liquid nitrogen 20. At the time of measurement, it is cooled to about -170 ° C. Further, the semiconductor detector 13 is placed as close as possible to the sample 24 in order to increase the detection sensitivity of characteristic X-rays. However, since the semiconductor detector 13 is disposed in the vacuum vessel 23, these are housed in the end cap 11, so An X-ray incident window 14 is attached to the tip of the.
Characteristic X-rays generated from the sample 24 are detected by the semiconductor detector 13 through this X-ray incident window 14, and after a pulse signal for each element is amplified by the proportional amplifier 16, energy selection of all elements is performed by the multichannel wave height selector 17. The spectrum of each characteristic X-ray is simultaneously displayed on the display device 18.
[0004]
Here, when an energy dispersive X-ray detection device is provided in an X-ray microanalyzer or the like and specific X-rays are detected by electron beam excitation, the excited characteristic X-rays are too strong. The collimator 1 for limiting the incident amount of the incident characteristic X-ray is disposed immediately before the X-ray incident window 14. In general, the collimator 1 has variable through-holes (collimator holes) of different sizes on a flat plate in order to make the incident limit variable, and which collimator hole 15 is used depending on the intensity of the characteristic X-ray to be measured. You can choose what to do.
[0005]
[Problems to be solved by the invention]
A conventional energy dispersive X-ray detection apparatus is configured as described above. In order to perform measurement more easily and in a short time, generally, a plurality of collimator holes 15 are formed on the same circumference of a flat plate. The shaft 2 fixed to the center of the circumference is manually rotated, or the shaft 2 is electrically rotated by using a drive motor 19 or the like, and an arbitrary collimator hole 15 on the collimator 1 is automatically set. The method of selection is taken.
However, in the method of rotating the shaft 2 manually, it is troublesome to select the collimator hole 15 for each measurement, and extra time is required for conversion. In the case of multiple holes, it is difficult to increase the positioning accuracy of the holes. On the other hand, in the method of driving with a motor, the semiconductor detector 13 for detecting characteristic X-rays is extremely vulnerable to electrical noise from disturbances, and even when the collimator 1 is driven, even the noise generated from the driving motor 19 is affected. End up. If these electric noises are superimposed on the electric signal processing circuit, the characteristic X-ray analysis will be seriously hindered.
The present invention has been made in view of such circumstances, and does not give electric noise to the electric signal processing circuit in driving when selecting the collimator hole 15 of the collimator 1 that limits the amount of incident X-rays. It is an object of the present invention to provide an energy dispersive X-ray detection apparatus that can select a collimator hole with high accuracy.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the energy dispersive X-ray detection apparatus of the present invention uses air pressure as a drive source for the collimator. Therefore, since electrical ON / OFF is not used for the drive unit of the collimator, generation of electrical noise does not occur. Furthermore, in the present invention, a collimator is installed facing the sample.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the energy dispersive X-ray detection apparatus of the present invention will be described below with reference to FIG.
FIG. 1A is a plan view of an energy dispersive X-ray detector X-ray incident amount limiting mechanism, and FIG. 1B is a front view thereof.
1A and 1B, reference numeral 1 denotes a collimator. A plurality of collimator holes 15 for limiting the characteristic X-ray dose incident on the semiconductor detector 13 are formed on the flat plate on the flat plate. The shaft 2 is attached to the center of the circumference.
Further, a lever fitting 3 is fastened to the shaft 2, and positioning screws 4a, 4b, 4c and nuts 5a, 5b, 5c are screwed to the lever fitting 3. The shaft 2 is fitted in the bearing portion of the base 10 and can rotate.
On the base 10, pneumatic cylinders 7a, 7b and a fixing metal fitting 9 are respectively arranged at positions opposite to the positioning screws 4a, 4b, 4c. The pneumatic cylinders 7a, 7b are respectively provided with piping tubes 8a, 8b. Connected.
[0008]
Further, a tension spring 6 is stretched between the base 10 and the lever fitting 3 to engage the two. Accordingly, the tip of any one of the positioning screws 4a, 4b, 4c is always in contact with the tip of the corresponding pneumatic cylinder 7a, 7b or the fixed metal fitting 9.
An end cap 11 is attached to the base 10, an X-ray incident window 14 is attached to the tip of the end cap 11 on the X-ray incident side, and the semiconductor detector 13 and the cold finger 12 are located inside the end cap 11. The other end is provided with a dewar 21 containing liquid nitrogen 20 in the same manner as the conventional energy dispersive X-ray detector, and the collimator hole 15 is incident on the X-ray. It is the same that it is arrange | positioned so that it may become the same center as the window 14. FIG.
[0009]
Next, the operation of the X-ray incident amount limiting mechanism of the energy dispersive X-ray detector of the embodiment shown in FIG. 1 will be described with reference to FIGS.
First, as shown in FIG. 2 (a), in the state where the pneumatic cylinders 7a and 7b are not operated, the positioning screw 4c is rotated and the center of the collimator hole 15c is brought into contact with the fixing metal fitting 9 while the tip of the screw is in contact. Is adjusted to match the center of the X-ray entrance window 14.
Next, as shown in FIG. 2B, compressed air is introduced into the piping tube 8b to operate the pneumatic cylinder 7b. When the cylinder extends by a predetermined stroke, the positioning screw 4b is rotated and adjusted so that the center of the collimator hole 15b coincides with the center of the X-ray incident window 14 with the tip of the screw contacting the tip of the piston rod. .
[0010]
Further, as shown in FIG. 2C, in a state where the pneumatic cylinder 7b is not operated, compressed air is introduced into the piping tube 8a to operate the pneumatic cylinder 7a. When the cylinder extends a predetermined stroke, the positioning screw 4a is rotated and adjusted so that the center of the collimator hole 15a coincides with the center of the X-ray incident window 14 with the tip of the screw contacting the tip of the piston rod. .
Finally, the nuts 5a, 5b, 5c of the respective positioning screws 4a, 4b, 4c are locked so that the positioning screws 4a, 4b, 4c do not move.
Since the center of the collimator hole 15 and the center of the X-ray incident window 14 are individually matched by screw adjustment, even if the processing angle accuracy of the collimator hole 15 is lowered, it can be matched with sufficiently high accuracy.
If the above adjustment is performed once in advance, in actual measurement, the flow of compressed air to the pneumatic cylinders 7a and 7b is turned ON / OFF according to a signal output from a controller (not shown) of the analyzer. Only the collimator holes 15a, 15b and 15c required at that time can be automatically selected.
In this embodiment, the collimator hole 15 is described as having three types. However, when a further multistage X-ray dose restriction is required, the set of the collimator hole 15 and the corresponding positioning screw 4 and pneumatic cylinder 7 may be increased. Further, although the nuts 5a, 5b, and 5c are used for fixing the positioning screws 4a, 4b, and 4c, the positioning screws may be fixed by pressing them with fixing screws from the lateral direction.
[0012]
In general, a solenoid valve using a solenoid (not shown) may be used to turn ON / OFF the compressed air flow into the pneumatic cylinder 7. In this case, the drive motor 19 according to the conventional example is mechanically used. Therefore, the semiconductor detector 13 and the preamplifier (not shown) must be placed in the vicinity. However, it is not necessary to place the solenoid valve necessary for the present invention in the vicinity of the semiconductor detector 13, so that if the piping tube 8 through which the compressed air flows is made sufficiently long, the semiconductor detector 13 is affected by electrical noise and the like. It is possible to install it freely at no distant position. Therefore, there is no influence on the semiconductor detector 13 by electrical noise generated by the electromagnetic valve.
[0013]
【The invention's effect】
The energy dispersive X-ray detection apparatus of the present invention is configured as described above, and a pneumatic cylinder using compressed air is used as a collimator drive source for limiting the X-ray dose incident on the semiconductor detector. It is possible to provide a system capable of automatically selecting collimator holes in a state in which no electrical noise is generated in the vicinity of the amplifier and the preamplifier and the electrical signal processing circuit is not affected by the electrical noise from the drive system. .
In addition, when a motor is used as the drive source, an attempt to increase the position accuracy of the collimator hole will result in a low speed, requiring a long time for switching, and in the case of manual switching, the troublesome switching operation and the collimator hole The problem of low position accuracy is eliminated.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an energy dispersive X-ray detection apparatus according to the present invention.
FIG. 2 is a diagram showing the operation of the energy dispersive X-ray detection apparatus of the present invention.
FIG. 3 is a diagram showing a conventional energy dispersive X-ray detector and X-ray analyzer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Collimator 2 ... Shaft 3 ... Lever metal fitting 4a, b, c ... Positioning screw 5a, b, c ... Nut 6 ... Tension spring 8 ... Pneumatic cylinder 9 ... Fixing metal fitting 13 ... Semiconductor detector 14 ... X-ray entrance window 15a , B, c ... Collimator holes

Claims (2)

An X-ray detector for detecting characteristic X-rays generated from a sample, and a plurality of collimator holes for limiting the amount of X-ray incidence are drilled in front of the X-ray entrance window of the detector so that the holes can be selected. An energy dispersive X-ray detection apparatus comprising a collimator driven by an air pressure, wherein air pressure is used as a drive source for the collimator. An X-ray microanalyzer characterized in that the collimator of the energy dispersive X-ray detection device according to claim 1 is installed facing a sample.

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