JPH0743642Y2 - X-ray diffractometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an X-ray diffractometer mainly applied when analyzing a sample of a radioactive substance.

(B) Conventional Technology When analyzing radioactive materials such as fuel for nuclear reactors using an X-ray diffractometer, the X-ray detector emits X-rays diffracted by the sample as well as the sample itself. Radiation of β rays and γ rays is simultaneously incident. Therefore, these become the background of the detection output and reduce the measurement sensitivity. In particular, γ-ray usually has a high energy of about 1 MeV and its intensity is also large, so that it is important to eliminate the influence.

As a countermeasure against this, in the conventional technology, a monochromator is installed on the optical path of X-rays for monochromatic X-rays, and a shield plate such as Pb or W is installed on a portion other than the optical path of X-rays, or wave height selection is performed. Measures have been taken such as energy selection based on the height of the X-ray detection pulse using a detector (PHS).

(C) Problems to be Solved by the Invention However, the conventional combination of a monochromator and a shielding plate and the method of using a wave height selector have the following problems.

i) When the shielding plate is provided, the movement range of the goniometer is restricted by the shielding plate, and therefore the diffraction angle (2
The range of θ) becomes small and it becomes impossible to measure a wide range.
In addition, a large shield plate is required to shield β-rays and γ-rays, but the weight added to the moving mechanism of the goniometer causes a positional shift in the optical axis relationship, which reduces analysis accuracy. Bring

ii) It is effective to distinguish the γ-rays and X-rays by selecting the height of the X-ray detection pulse, but β-rays and γ-fibers have a wide range of energy, and the scattered rays due to Compton scattering etc. have a low energy. Therefore, it is difficult to separate them from the diffracted X-rays.

The present invention has been made in view of such circumstances, and when analyzing a sample of a radioactive substance, effectively removes the influence of β rays and γ rays from the sample without degrading the accuracy of the goniometer. The purpose is to obtain a non-linear diffraction result with a good S / N ratio.

(D) Means for Solving the Problems In order to achieve the above object, the present invention irradiates a sample with X-rays and detects the X-rays diffracted by the sample with an X-ray detector. In, the following configuration is adopted.

That is, according to the present invention, an intermittent means for intermittently interrupting the X-rays irradiated on the sample in a time division manner, a timing pulse generating means for outputting a timing pulse for regulating the intermittent timing of the intermittent means, and a timing pulse synchronizing with the timing pulse. A switching circuit for switching the output of the X-ray detector, a storage unit for individually storing each output signal from the switching circuit, and a subtraction circuit for subtracting both signals stored in the storage unit are provided. .

(E) Operation According to the above configuration, the interrupting device interrupts the X-rays applied to the sample in time division in synchronization with the timing pulse from the timing pulse generating device. Therefore, the radiation emitted from the sample such as β rays and γ rays together with the diffracted X-rays is simultaneously incident on and detected by the X-ray detector when the intermittent means is released. On the other hand, when the disconnecting means is shut off, the diffraction X
No rays are incident, and only γ-ray and β-ray radiation from the sample is detected. Then, since the switching circuit switches the output of the X-ray detector in synchronization with the timing pulse, each detection output obtained according to the interruption is separately stored in the storage means of the next stage. Since both signals individually stored in the storage means are subtracted by the subtraction circuit, the analysis result of only the diffracted X-rays in which the background caused by γ-rays or β-rays is removed can be obtained.

(F) Embodiment FIG. 1 is a configuration diagram of an X-ray diffraction apparatus according to an embodiment of the present invention. In the figure, 1 indicates the entire X-ray diffractometer,
2 is a sample made of radioactive material such as plutonium, 4 is X
X-ray tube that emits X-ray, 6 is diffraction X diffracted by sample 2
An X-ray detector for detecting rays, for example, a proportional coefficient tube or a scintillation coefficient tube is used. Then, the sample 2 and the X-ray detector 6 are placed on the goniometer 8 and Br.
Move to satisfy the agg diffraction condition.

Reference numeral 10 denotes an interrupting means for interrupting the X-rays applied to the sample 2 in a time division manner, and in this example, it comprises a pulse motor 12 and a rotary slit 14 fixed to the rotary shaft thereof. Rotating slit 14
Is divided equally in the circumferential direction as shown in FIG.
The chopping blade 16 has an area ratio set so that the duty ratio of the line becomes 50%. The chopping blade 16 is located on the X-ray irradiation path L between the X-ray tube 4 and the sample 2. It is provided to do. Reference numeral 18 is a timing pulse generating means for outputting a timing pulse for regulating the intermittent timing of the intermittent means 10, and 20 is this timing pulse generating means.
A switching circuit for switching the detection output of the X-ray detector 6 in synchronization with a timing pulse from 18, and 22 is a storage means for individually storing each output signal from the switching circuit 20. In this example, detection of the switching circuit 20 is performed. It is composed of two counters 22a and 22b for individually counting the pulses. 24 is both counters 22a, 2
It is a subtraction circuit that subtracts both count values counted in 2b.

Next, the operation of analyzing the sample 2 of the radioactive substance in the X-ray diffractometer 1 having the above structure will be described.

In the analysis, the timing pulse generating means 18 outputs the timing pulse shown in FIG. 3 (a), and the timing pulse is given to the pulse motor 12 and the switching circuit 20, respectively. The pulse motor 12 is driven in synchronization with this timing pulse, and the chopping blade 16 of the rotary slit 14 intermittently interrupts the X-ray emitted from the X-ray tube 4 toward the sample 2 in a time division manner. In this case, since the chopping blade 16 is equally divided in the circumferential direction, the duty ratio of the X-rays with which the sample 2 is irradiated is 50%. When the chopping blade 16 is not located on the X-ray irradiation optical path L, the X-ray from the X-ray tube 4 is diffracted by the sample 2, so that the X-ray detector 6 causes β along with the diffracted X-ray. Rays and γ rays are simultaneously incident and detected (see FIG. 3 (b)).
On the other hand, the chopping blade 16 of the rotary slit 14 is X
X is located on the X-ray irradiation path L between the tube 4 and the sample 2.
When the rays are blocked, the diffracted X-rays from the sample 2 do not enter the X-ray detector 6, and only the γ-rays and β-rays emitted from the sample 2 are detected (FIG. 3 (c)). reference).

On the other hand, the switching circuit 20 switches the output of the X-ray detector 6 in synchronism with the timing pulse.
The output of the X-ray detector 6 is connected to one counter 22a at the timing when the X-ray and the γ-ray are simultaneously detected, and is connected to the other counter 22b at the timing when only the radiation emitted from the sample 2 is detected. Therefore, the counter 22a on one side detects the detection pulse (S) caused by the diffraction X-ray.
In addition, detection pulses (S + N) including noise components (N) caused by radiation such as γ rays and β rays are counted,
The other counter 22b counts the detection pulse of only the noise component (N) of the radiation (γ ray, β ray) emitted from the sample 2. The count values individually counted by the counters 22a and 22b are subtracted by the subtraction circuit 24 to calculate the difference, so only the diffracted X-rays from which the background caused by γ-rays or β-rays have been removed. The analysis result S of is obtained. In this embodiment, the chopping blade 16 of the rotary slit 14 has a duty ratio of X-rays passing through it of 50%.
Although the area ratio is set so as to satisfy the above condition, the area ratio is not necessarily limited to this, and may be any as long as a constant duty ratio can be obtained. In this case, it is necessary to correct the count value of the counter 22b that counts radiation such as γ rays and β rays. Further, as the intermittent means, for example,
The X-ray source itself may be interrupted by, for example, turning on / off the electron beam from the filament of the X-ray tube 4 using a deflection plate to interrupt the irradiation of the thermoelectron beam.

(G) Effect According to the present invention, in the analysis of radioactive substances, β rays and γ rays from the sample can be obtained without degrading the accuracy of the goniometer.
Excellent effects such as effective removal of the influence of the rays and obtaining of measurement results of X-ray diffraction with a good S / N ratio are exhibited.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a block diagram of an X-ray diffractometer, FIG. 2 is a front view of a rotary slit, and FIG. 3 is a relationship between a timing pulse and a detection output of an X-ray detector. 2 is a timing chart showing 1 ... X-ray diffractometer, 2 ... Sample (radioactive material), 4 ...
… X-ray tube, 6… X-ray detector, 10… Intermittent means, 18…
… Timeig pulse generator, 20 …… Switching circuit, 22 ……
Storage means, 24 ... Subtraction circuit.

Claims (1)

[Scope of utility model registration request] 1. A sample is irradiated with X-rays and X is diffracted by the sample.
In an X-ray diffractometer for detecting X-rays with an X-ray detector, an intermittent means for intermittently time-sharing the X-rays irradiated on the sample, and a timing pulse generation for outputting a timing pulse for regulating the intermittent timing of the intermittent means. Means, a switching circuit for switching the output of the X-ray detector in synchronization with the timing pulse, a storage means for individually storing each detection signal from the switching circuit, and both signals stored in the storage means. An X-ray diffraction device comprising: a subtraction circuit for subtracting.