JPS5932731B2 - radiation analyzer - Google Patents

Description

[Detailed Description of the Invention] This invention provides, for example, electrolytic chromic acid treated steel plate tin plate,
A radiation analyzer that non-destructively measures the thickness of a plating layer of chromium, tin, zinc, etc. on galvanized iron, or the content of low-concentration elements in a sample, detects changes in the radiation intensity of a radiation source. This invention relates to a radiation analyzer that maintains the radiation intensity constant.

For example, among various radiation analyzers, in fluorescent When used, it is an important requirement to obtain stable performance over a long period of time.

When an X-ray tube (hereinafter referred to as a tube) is used as a radiation source, stable X-ray intensity has traditionally been obtained using a method that uses the tube's power source to keep the tube voltage and tube current constant. I was trying.

However, with this method, it is difficult to obtain an X-ray output of constant intensity due to changes in the state of the target. When measuring the thickness of a very thin plating layer, there is a method of detecting the characteristic X-rays of the base metal layer and the characteristic X-rays of the plating layer at the same time, and calculating the intensity ratio of these (hereinafter referred to as the ratio method). There is.

According to this method, short-term fluctuations in the X-ray intensity can be corrected, but the tube is contaminated with target and
This shows long-term fluctuations in which the X-ray intensity gradually decreases due to factors such as dirty windows. In the ratio method, measurement accuracy deteriorates as the X-ray intensity decreases. This invention was made to solve the above-mentioned drawbacks, and it is possible to monitor the long-term fluctuation of the decrease in radiation intensity of a radiation source by detecting radiation generated from a standard material. By controlling the tube current of the radiation power source tube,
It is an object of the present invention to provide a radiation analyzer that keeps radiation intensity almost constant and always has stable measurement accuracy and measurement time.

The present invention will be described below based on embodiments shown in the accompanying drawings.

FIG. 1 shows the configuration of an embodiment of the present invention, in which 1 is an object to be measured, for example, an iron plate having a plating layer such as an electrolytic chromic acid treated steel plate, 2 is a measuring head, and 4 is the inside of this measuring head 2. The tube is built in and placed facing the measurement window 3, and is supplied with high voltage and filament current from 11 X-ray sources.

X@Xo generated from the tube 4 is irradiated onto the object 1 to be measured. A part of this irradiated X-ray XO is
They are absorbed by the plating layer, and characteristic X-rays of the element, such as chromium, are generated from the plating layer. Also, X-rays. A part of the iron passes through the plating layer and enters the base metal layer such as iron, and characteristic X-rays of iron are generated. In this case, the former characteristic X-rays of chromium are passed through a filter 5 to a scintillation counter tube 7.
Detected by radiation detectors such as The latter iron characteristic X-rays are detected by a detector 8 through a filter 6.

In this case, the two types of filters 5 and 6 (hereinafter referred to as balanced filter 1) are used for radiation detectors (hereinafter referred to as detectors) with poor resolution, such as proportional counters and scintillation counters. In this case, it is used to separate characteristic X-rays having energy values that are close to each other beyond the separation capability of the detector.

That is, in the absorption coefficient curve for explaining the principle of the balanced filter shown in FIG. 2, the vertical axis is the absorption coefficient on a logarithmic scale, and the horizontal axis is the energy of the characteristic X-ray. In the figure, E1 is the energy of the characteristic X-ray of the element to be measured to be detected, and E2 is the energy of the characteristic X-ray of the interfering element. A is the energy E of the above measurement target
This is the absorption curve of element A with an absorption edge at an energy value smaller than 1 and close to this energy E,. B is an absorption curve of an element having an absorption edge with an energy value smaller than the energy E2 of the interfering element and larger than the energy E1 of the element to be measured. In the X-rays that have passed through the filter of element B', the characteristic X-rays of the interfering element having energy value E2 are absorbed more, and the characteristic X-rays of the element to be measured having energy value E, are absorbed more. Transmits a lot. Furthermore, in the X-rays that have passed through the filter of element N, the characteristic X-ray that becomes a disturbing element and has an energy value of E2 is absorbed to the same extent as when it has passed through the filter of element B', and has an energy value of E2. The characteristic X-rays of the measured element having E1 are absorbed more. As a result, the intensity of the characteristic X-ray of the element to be measured can be measured based on the output ratio of the detectors that detected the X-rays transmitted through element B' and element N, or the output difference between the respective detectors. This balanced, filtered method satisfies the requirements of industrial instrumentation, especially in on-line systems, such as short response time, low cost, easy maintenance, minimal reduction in radiation intensity, etc. When separating characteristic X-rays, it is superior to semiconductor detectors or wavelength dispersive analyzers.

In this way, the output signals of characteristic X-rays of chromium and iron generated from the plating layer by counters 7 and 8, respectively, are then transmitted to waveform shaping amplifiers 9, 10 and pulse height analyzers 12, 13.
are sequentially applied to each of them, and are waveform-shaped and amplified, and are converted into pulse signals of characteristic X-rays of chromium and characteristic X-rays of iron. Thereafter, the pulse signals of the respective characteristic X-rays of chromium and iron outputted from the wave height analyzers 12 and 13 are applied to rate meters 26 and 27, and the ratio is calculated by a calculator 28 for data processing. The circuit 23 converts it into the thickness of the plating layer, and displays or prints it out. In this case, the characteristic X-rays of iron are transmitted to the tube 4.
It acts as a detection signal for correcting changes in the intensity of X-rays generated from the X-rays.

That is, the circuit configuration for correcting the intensity change of the X-rays generated from the tube 4 includes an A-G-C circuit 14 to which the output signal of the rate meter 27 is applied, and an X-ray power source 11. .

Now, for example, if the intensity of the characteristic X-rays of iron changes, the content of the output signal from the rate meter 27 changes accordingly, so the A
- When the G-C circuit 14 operates and appropriately changes the filament current of the X-ray power source 11, the tube current flowing through the tube 4 changes, and the intensity of the X-rays generated from the tube 4 changes constantly. Correct to stabilize. Further, the circuit configuration for correcting the change in the characteristics of the counter tube 8 includes a correction radiation source 29 for supplying radiation of a constant intensity to the counter tube 8.
a rate meter 30 that converts the radiation intensity of the correction radiation source 29 separated by the pulse height analyzer 13 into an analog signal; It consists of an A-G-C circuit 31 for changing the high voltage value of a voltage source 32 applied to the device 8.

In this circuit, it is desirable that the energy level of the radiation of the correction radiation source 29 can be distinguished by the wave height analyzer 13 from the energy level of characteristic X-rays peculiar to the metal of the plating layer that is the object to be measured; For example, gamma rays from americium 241, which have a higher X-ray energy level than iron in the plating layer, are preferable.

The wave height spectra of the γ-rays of americium-241 and the X-rays of iron are shown in FIG. Therefore, the operation of the circuit for correcting the change in the characteristics of the counter tube 8 is as follows. That is, now,
When the detection characteristics of the radiation detector 8 change, the peak value of the correction radiation source 29 changes.

As a result, the output signal of the A-G-C circuit 31 to which the output signal of the pulse height analyzer 30 is applied via the rate meter 30 is determined by the pulse height analysis. The detection characteristics of the radiation detector 29 are stabilized by changing according to changes in the output signal value of the radiation detector 30. On the other hand, the means for correcting changes in the detection characteristics of the radiation detector 7 is as in the case of the radiation detector 8 described above.
The correction circuit includes a correction radiation source 33 and a rate meter 3.
4, an A-G-C circuit 35, a voltage source 36, etc.,
The change in the output signal output from the pulse height analyzer 12 is
The voltage of the voltage source 36 is sequentially applied to the rate meter 34, the A-G-C circuit 35, and the voltage source 36, and the voltage of the voltage source 36 applied to the insufficient or excessive radiation detector 7 is controlled to adjust the detection characteristics of the radiation detector 7. Stabilize.

Next, referring to FIG. 4, another embodiment will be described.

This embodiment uses one radiation detector 41 to detect two types of X-rays, whereas the previous embodiment uses two radiation detectors 7 and 8 to separately detect two types of X-rays. This is an example that satisfies the functions. This is a case where the wave height values of the sample 42 and the calibration sample 43 can be identified by one radiation detector 41, and in this case, the wave height spectra of the sample 42, the calibration sample 43, and the correction radiation source 44 are The result will be as shown in the figure. That is, the radiation detection device of this example has
The sample 42 and the calibration sample 43 are simultaneously irradiated with X-rays emitted from the ray tube 45, thereby generating X-rays specific to the substances generated by the samples 42, 43.

The two types of characteristic X-rays generated from the samples 42 and 43 are:
They simultaneously enter the detector 41. This result, the detector 4
1, the two types of characteristic X-rays and radiation from a correction radiation source (for example, americium 241) 44 are detected. The three types of radiation detected by this detector 41 become three types of output signals and are sent to the waveform shaping amplifier 45.
, are sequentially applied to the pulse height analyzer 46. As a result, the output signals of the waveform analyzer 46 become three types of output signals corresponding to the calibration sample 43, the sample 42, and the correction radiation source 44, respectively. The power is sequentially applied to the -GC circuit 48 and the X-ray tube power source 49, thereby stabilizing the intensity of the X-rays output from the X-ray tube 45. Further, the output signal of the pulse height analyzer 46 corresponding to the X-rays of the sample 43 is applied to the rate meter 50 and the calculation data processing circuit 51.

In this case, since the output signal of the pulse height analyzer 46 corresponding to the calibration sample 43 is applied to the calculation data processing circuit 51 via the rate meter 47, these two pieces of information are calculated and data processed. . Furthermore, the output signal of the pulse height analyzer 46 based on the radiation of the correction radiation source 44 is sequentially applied to the rate meter 52, the A-G-C circuit 53, and the voltage source for the detector, thereby changing the detection characteristics of the detector 41. We are measuring stabilization.

As described above, in the apparatus of the present invention, a sample is irradiated with radiation emitted from a radiation source, and the characteristic X-rays generated from the sample are sequentially passed through a predetermined detector and other circuits to control the intensity of the radiation emitted from the radiation source. Since the voltage applied to the A/G-C circuit and the voltage applied to the radiation source is controlled, the radiation intensity of the radiation source is extremely stable.

In addition, by injecting radiation with stable radiation intensity into the radiation detector, when the detection characteristics of the radiation detector change, the change in radiation intensity is detected accordingly, and the radiation detector Since the drive voltage is controlled, a radiation detector with extremely stable detection characteristics can be obtained. Furthermore, when the radiation energy level of the sample and the radiation energy level of the calibration sample are extremely close, sample measurement using the balance filter method can reliably separate the two types of peak values, resulting in extremely accurate sample measurement. It is possible. Note that the sample and the calibration sample may be different. In addition, in a combination of a certain metal and a metal attached by plating or the like, or in a metal consisting of two or more metals in one body such as a low concentration alloy, at least one of the metals One may be determined as a calibration metal and the components, concentration, thickness, etc. of other contained or attached metals may be measured.

[Brief explanation of drawings]

The figures show an embodiment of the present invention; FIG. 1 is a block diagram of a radiation analyzer showing the first embodiment, and FIG. 2 is an absorption coefficient curve diagram of a balance filter. , and FIG. 3 is a graph of the wave height spectrum. Furthermore, FIG. 4 is a block diagram of a radiation analyzer according to another embodiment. FIG. 5 is a graph of the wave height spectrum. 4...radiation source, 11...
...Power supply, 8...Radiation detector, 13...
... Wave height analyzer, 14... A/G-C circuit,
29... Standard radiation source, 30... Route meter, 31... A-G-C circuit, 12...
...Wave height analyzer.

Claims (1)

[Claims] 1. An X-ray tube for irradiating the sample and the calibration sample with X-rays, a common detector for detecting secondary X-rays from the sample and the calibration sample, and a common detector connected to the detector. a waveform shaping amplifier; a pulse height analyzer connected to the waveform shaping amplifier; and a rate meter connected to the pulse height analyzer;
an AGC circuit connected to the rate meter; and an AGC circuit connected to the rate meter;
and an X-ray tube power source connected to the C circuit, and configured to stabilize the X-ray tube power source via the AGC circuit using secondary X-ray data from the calibration sample. Radiation analysis equipment.