JP2010078521A - Counting rate measuring device and counting rate measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend an exchange period of a pulse-type radiation detector. <P>SOLUTION: The counting rate measuring device includes: the pulse-type radiation detector 1 which measures radiation; a band-pass filter 2 which attenuates unnecessary signal of an output signal of the pulse type radiation detector 1; an amplifier 3 which amplifies the output signal of the band pass filter; and an operation processing part 6 which carries out counting of the output signal of amplifier 3 and calculates the radiation dosage. The band-pass filter 2 is such that by making low-frequency side larger than high-frequency side for the gain of frequency component of the pulse-type radiation detector 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a count rate measuring apparatus and a count rate measuring method for counting pulse signals from a pulse output type radiation detector.

The conventional counting rate measuring apparatus counts the pulse output signal from the pulse output type radiation detector by amplifying it with an amplifier after removing unnecessary signals through a bandpass filter. The band-pass filter is a band-pass filter that combines a high-pass filter and a low-pass filter (see, for example, Patent Document 1).
JP 2005-24465 JP

In the above-described counting rate measuring apparatus, the pulse radiation detector has a gas amplification factor that decreases due to the accumulation of radiation irradiation, the wave height of the output signal decreases, and the S / N ratio deteriorates. As the recombination rate increases, the frequency band of the output signal shifts to the low frequency side. Even if the pulse-type radiation detector is not yet at the end of its life, when the S / N ratio falls below a certain value, the pulse-type radiation detector has been determined to be at the end of life and has been replaced. Conventionally, the pulse-type radiation detector has been replaced in about 0.3 times the pulse sensitivity of the initial state and 6 cycles in the operation cycle of the reactor.

In order to solve these problems, an object of the present invention is to extend the replacement time of a pulsed radiation detector.

A counting rate measuring apparatus according to the present invention includes a pulse-type radiation detector that measures radiation, a band-pass filter that attenuates an unnecessary signal of the output signal of the pulse-type radiation detector, and outputs the radiation by counting the output signal of the band-pass filter. And a band-pass filter characterized in that the gain of the frequency component of the pulse radiation detector is larger on the low frequency side than on the high frequency side.

Also, the counting rate measuring method of the present invention measures radiation with a pulse radiation detector, and an unnecessary signal of the output signal of the pulse radiation detector with a bandpass filter having a gain on the low frequency side larger than the gain on the high frequency side. And the radiation dose is calculated by counting the output signal of the bandpass filter.

According to the present invention, the replacement time of the pulse radiation detector can be extended.

Hereinafter, embodiments of a counting rate measuring apparatus and a counting rate measuring method according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of a counting rate measuring apparatus according to the present invention.

The count rate measuring apparatus according to the first embodiment includes a pulse-type radiation detector 1 that measures radiation, and a band filter that receives a pulse output signal from the pulse-type radiation detector 1 and attenuates an unnecessary signal to shape a waveform. 2, the amplifier 3 that amplifies the output signal of the bandpass filter 2, the discrete voltage setting circuit 5 that outputs a certain voltage, and the output signal of the amplifier 3 and the output voltage of the discrete voltage setting circuit 5 are compared. In the case of an effective signal, the comparator 4 is configured to output a signal, and the arithmetic processing unit 6 is configured to calculate the radiation dose by counting the output signal of the comparator 4. The band filter 2 includes a high-pass filter 7 having a cutoff frequency f1, a first low-pass filter 8 having a cutoff frequency f2, and a second low-pass filter 9 having a cutoff frequency f3.

The filter characteristics of the band filter 2 are shown in FIG. The relationship between the cutoff frequency f1 of the high-pass filter 7, the cutoff frequency f2 of the first low-pass filter 8, and the cutoff frequency f3 of the second low-pass filter 8 is f1 <f2 <f3.

In the present embodiment configured as described above, the pulse radiation detector 1 is used for a long period of time, and the gas amplification factor decreases due to the accumulation of radiation irradiation, the wave height of the output signal decreases, and the S / N ratio deteriorates. The frequency band of the output signal is shifted to the low frequency side by increasing the recombination rate inside the pulse type radiation detector, but the gain of the frequency component of the pulse type radiation detector 1 is lower than the high frequency side. Is set, that is, the filter characteristic of the band filter 2 is set so that the gain is increased by an amount that compensates for the decrease in the wave height of the output signal due to the long-term use of the pulse radiation detector 1. In this way, the output wave height of the bandpass filter 2 is kept unchanged even after long-term use.

According to the present embodiment, even if the output characteristics of the radiation detector 1 change due to the accumulation of radiation irradiation, the wave height of the output signal of the bandpass filter 2 does not change, and the frequency component of noise does not change due to the accumulation of radiation irradiation. Therefore, since the S / N ratio can be stabilized over a long period of time, the replacement time of the pulse radiation detector can be extended.

FIG. 3 is a diagram showing a second embodiment of the counting rate measuring apparatus according to the present invention.

The counting rate measuring apparatus according to the second embodiment has a calibration circuit 10 that outputs a signal simulating the output signal of the pulse radiation detector 1 and the output of the pulse radiation detector 1 in the configuration of the first embodiment. The signal switching unit 11 selects a signal and a calibration signal of the calibration circuit 10 and outputs the selected signal to the bandpass filter 2.

In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the present embodiment configured as described above, the pulse-type radiation that changes due to the accumulation of radiation irradiation by adjusting the fall, rise, pulse width, repetition period, and wave height of the pulse signal of the calibration signal of the calibration circuit 10. The output signal of the detector 1 is simulated.

According to the present embodiment, the waveform of the output signal of the pulse radiation detector 1 that changes due to the accumulation of radiation irradiation can be simulated by the calibration circuit 10.

The above description is merely an example, and the present invention is not limited to the above-described embodiment, and can be implemented in various forms.

The figure which shows 1st Embodiment of the count rate measuring apparatus in this invention. The figure which shows the filter characteristic of a band pass filter. The figure which shows 2nd Embodiment of the count rate measuring apparatus in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulse type radiation detector 2 Bandpass filter 3 Amplifier 4 Comparator 5 Discrete voltage setting circuit 6 Arithmetic processing part 7 High pass filter 8 1st low pass filter 9 2nd low pass filter 10 Calibration circuit 11 Signal switching part

Claims (6)

A pulsed radiation detector for measuring radiation;
A bandpass filter for attenuating unwanted signals of the output signal of the pulse-type radiation detector;
An arithmetic processing unit that calculates the radiation dose by counting the output signal of the bandpass filter,
The band-pass filter increases the gain of the frequency component of the pulse-type radiation detector on the low frequency side from the high frequency side. The bandpass filter includes a high-pass filter, a first low-pass filter, and a second low-pass filter,
The count rate measuring apparatus according to claim 1, wherein the first low-pass filter and the second low-pass filter have different cutoff frequencies. 2. The count rate measurement according to claim 1, wherein the frequency characteristic of the band-pass filter is a filter characteristic in which a gain is increased by compensating for a decrease in a wave height of an output signal due to long-term use of the pulse-type radiation detector. apparatus. A calibration circuit that outputs a signal simulating the output signal of the pulse radiation detector;
2. The counting rate measuring apparatus according to claim 1, further comprising a signal switching unit that selects an output signal of the pulse radiation detector and a calibration signal of the calibration circuit and outputs the selected signal to the bandpass filter. 5. The counting rate measuring apparatus according to claim 4, wherein the calibration circuit can adjust a falling edge, a rising edge, a pulse width, a repetition period, and a wave height of an output pulse signal. Measuring radiation with a pulsed radiation detector,
Attenuate the unnecessary signal of the output signal of the pulse type radiation detector with a bandpass filter with a gain on the low frequency side larger than the gain on the high frequency side,
A counting rate measuring method, wherein the radiation dose is calculated by counting the output signal of the bandpass filter.

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