JP2000075037A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and stably measure a dynamic range that is wide from a low radiation level to a high radiation level. SOLUTION: An ionization-box-type radiation detector for detecting radiation by measuring an ionization current due to the incidence of radiation by applying the measuring principle of an ionization box is provided with first and second cathode electrodes 11 and 12 where each different voltage is applied and an anode electrode 13. The radiation detector is provided with a pulse count means 19 by alternately arranging a plurality of at least one second cathode electrode 12 and anode electrode 13 at a position opposite to the first cathode electrode 12, inputting a signal from the anode electrode 13, and outputting a pulse each time when a signal with a larger signal than a predetermined wave-height discrimination level is inputted and an external output means 110 that inputs a pulse from the pulse count means 19 for performing operation, instructing and outputting the operation result, or has a function for outputting a signal to the outside in a signal form being requested from the outside such as an alarm signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ionization chamber type radiation detector used in, for example, a nuclear facility, or an ionization chamber type radiation detector used in an experiment using radiation. The present invention relates to a radiation detector capable of performing accurate and stable measurement over a wide dynamic range from to high radiation levels.

[0002]

2. Description of the Related Art Conventionally, in nuclear facilities, for example, ionization chamber type radiation detectors for measuring ionization current due to radiation by applying the measurement principle of ionization chambers have been widely used.

FIG. 12 is a schematic diagram showing an example of this type of conventional ionization chamber type radiation detector. 12, the ionization chamber type radiation detector 120 includes a cathode electrode 121 and an anode electrode 122 facing each other, and a high-voltage power supply 1.
23, the feed-through current introduction terminal 124, and the detector container 12
8, a cable 125, a signal measurement circuit 126, and an external output circuit 127, as shown in the figure.

A cathode electrode 121 and an anode electrode 122
Is filled with an argon gas 129 as a radiation detection medium. When the radiation enters the ionization chamber type radiation detector 120, the argon gas 129
Interacting with each other to generate argon ions and electrons in quantities corresponding to the energy applied to the argon gas 129.

[0005] The high voltage power supply 123 causes the cathode electrode 1
By applying a negative voltage to 21 and measuring the anode electrode 122 at ground potential, argon ions are collected on the cathode electrode 121 and electrons are collected on the anode electrode 122. Therefore, the anode electrode 122
Is connected to a signal measuring circuit 126 to measure the ionization current due to the incidence of radiation.

[0006]

However, in the ionization chamber type radiation detector 120 as described above, since the ionization current due to the interaction between radiation and argon is used, a very weak output on the picoampere order is used. Only current can be obtained.

Therefore, as a method of increasing the ionization current, for example, a method of increasing the pressure of the argon gas 129 sealed in the detector can be considered. In this case, the output current is saturated when the radiation level is high. There is fear.
Therefore, the method of increasing the pressure of the argon gas 129 cannot secure a wide dynamic range of about 10 decards.

For this reason, at present, the ionization current is very small near the lower limit of the measurement range, and it is necessary to take measures such as electromagnetic shielding and high-precision measurement circuits in order to ensure the stability of operation. The problem is that it is impossible to stably measure up to the above low radiation level.

An object of the present invention is to provide a radiation detector capable of performing accurate and stable measurement over a wide dynamic range from a low radiation level to a high radiation level.

[0010]

In order to achieve the above object, an ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the ionization chamber measurement principle. According to the first aspect of the present invention, there is provided the first and second cathode electrodes to which different voltages are respectively applied, and an anode electrode, and at least one second electrode is provided at a position facing the first cathode electrode. A pulse counting means for receiving a signal from the anode electrode and outputting a pulse each time a signal larger than a predetermined peak height discrimination level is inputted; and a pulse counting means. Inputs a pulse from the controller and performs an operation, and outputs the operation result as an instruction or outputs a signal to the outside in the form of a signal required from the outside such as an alarm signal. And an external output means having a function of performing.

Therefore, in the radiation detector according to the first aspect of the present invention, the first cathode electrode and the second cathode electrode.
The electrons generated in the argon gas by the action of the electric field formed by the anode electrode drift to the vicinity of the second cathode electrode or the vicinity of the anode electrode. Then, energy is obtained from the high electric field formed by the second cathode electrode and the anode electrode, so-called gas multiplication occurs, and the increased signal is collected by the anode electrode. At this time, since a short pulse signal appears in the signal measuring circuit, pulse counting can be performed.

According to a second aspect of the present invention, there are provided first and second cathode electrodes to which different voltages are applied, respectively, and an anode electrode, wherein at least one of the first and second cathode electrodes is located at a position facing the first cathode electrode. A plurality of the second cathode electrodes and the plurality of anode electrodes are alternately arranged, a signal from the anode electrode is input, and the input signal is branched into a signal in a frequency band for pulse counting and a signal in a frequency band for current measurement. Frequency band filter means, a pulse count frequency signal from a frequency band filter means, and a pulse count means for outputting a pulse each time a signal greater than a predetermined pulse height discrimination level is input; and The signal of the frequency band for current measurement from the band filter means is input, and the DC component is extracted to obtain a current value (ionization current). The first current measuring means to be detected, the pulse from the pulse counting means, and the current value from the first current measuring means are input to perform an operation, and the operation result is requested from an external device such as an instruction output or an alarm signal. External output means having a function of outputting a signal to the outside in a signal form to be provided.

Therefore, in the radiation detector according to the second aspect of the present invention, the pulse component and the current component are separated by the action of the frequency band filter circuit provided at the input stage of the signal measuring circuit, so that not only the pulse counting but also the pulse counting is performed. Current measurement can also be performed.

According to a third aspect of the present invention, in the radiation detector according to the first aspect of the present invention, instead of the pulse counting means, a signal of a frequency band for pulse counting from a frequency band filter means is input, Each time a signal greater than a predetermined pulse height discrimination level is input, a pulse is output, and a pulse counting means is provided for separately outputting a signal before pulse height discrimination, and a signal before pulse height discrimination from the pulse counting means is input. Then, a means for reconstructing a current value (ionization current) based on a signal from the anode electrode based on the pulse height and the pulse arrival frequency is added.

Accordingly, in the radiation detector according to the third aspect of the present invention, the pulse component and the current component are separated by the action of the frequency band filter circuit provided at the input stage of the signal measurement circuit, and the pulse count and the current measurement are performed. The current output is reconstructed from the pulse count frequency and the peak value, and the upper limit of the pulse countable area can be known.

On the other hand, according to the invention of claim 4, there are provided first and second cathode electrodes to which different voltages are applied, respectively, and an anode electrode, and at least one of the first and second cathode electrodes is provided at a position opposed to the first cathode electrode. A second current measuring means for alternately arranging a plurality of second cathode electrodes and anode electrodes, measuring an ionization current based on a signal from the first cathode electrode, and a signal from the anode electrode as an input; A pulse counting means for outputting a pulse every time a signal greater than a predetermined wave height discrimination level is input, a pulse from the pulse counting means, and a current value from the second current measuring means are inputted to perform an operation. External output means having a function of outputting the operation result as an instruction or outputting a signal to the outside in a signal form required from the outside such as an alarm signal.

Therefore, in the radiation detector according to the fourth aspect of the present invention, the number of pulses can be counted by connecting the pulse counting circuit to the anode electrode. Further, by connecting a current measuring circuit to the first cathode electrode, it is possible to measure an ionization current due to argon ions which is not affected by electron multiplication between the second cathode electrode and the anode electrode.

According to the fifth aspect of the present invention, there is provided the third aspect of the present invention.
In the radiation detector according to the invention, a second current measuring means for measuring an ionization current based on a signal from the first cathode electrode is added, and the second output stored in the external output means in advance. The relationship between the voltage applied to the cathode electrode and the gas multiplication rate, the pulse from the pulse counting means, the current value from the means for reconstructing the current value, and the respective currents from the first and second current measuring means. A determination function for checking whether or not the pulse count is saturated based on the value is added.

Therefore, in the radiation detector according to the fifth aspect of the present invention, the relationship between the voltage applied to the second cathode electrode and the gas growth rate is obtained by a calibration test, and the result is stored in an appropriate storage unit in the signal measurement circuit. And reading the result at the time of signal measurement, dividing the ionization current calculated from the pulse wave height and the count rate by the gas multiplication rate to obtain the current obtained at the first cathode electrode by calculation. By comparing this with the result obtained by a circuit for reconstructing the ionization current actually connected to the first cathode electrode, the radiation level is monitored while confirming that the pulse count is not saturated. be able to.

Further, according to the invention of claim 6, there are provided first and second cathode electrodes to which different voltages are applied, respectively, and an anode electrode, and at least one of the first and second cathode electrodes is provided at a position opposed to the first cathode electrode. A plurality of the second cathode electrodes and the plurality of anode electrodes are alternately arranged, a signal from the anode electrode is input, and the input signal is branched into a signal in a frequency band for pulse counting and a signal in a frequency band for current measurement. Frequency band filter means, a pulse count frequency signal from a frequency band filter means, and a pulse count means for outputting a pulse each time a signal greater than a predetermined pulse height discrimination level is input; and A signal in a frequency band for current measurement from a bandpass filter is input, and an effective voltage (RMS voltage) of the input signal is measured. RMS voltage is output as an RMS voltage, a pulse from the pulse counting means, and an RMS voltage from the RMS voltage are input to perform an operation, and the operation result is requested from an external device such as an instruction output or an alarm signal. External output means having a function of outputting a signal to the outside in a signal form to be provided.

Therefore, in the radiation detector according to the sixth aspect of the present invention, an RMS voltage output proportional to the radiation signal can be obtained by the action of the frequency band filter circuit at the input stage of the signal measurement circuit from the second cathode electrode. By providing a frequency band filter capable of performing frequency band and pulse counting, not only pulse measurement and RMS voltage measurement from the anode electrode but also ionization current measurement from the first cathode electrode can be performed.

On the other hand, according to the invention of claim 7, there are provided first and second cathode electrodes to which different voltages are applied, respectively, and an anode electrode, and at least one of the first and second cathode electrodes is provided at a position facing the first cathode electrode. A first current measuring means for alternately arranging a plurality of second cathode electrodes and anode electrodes to measure an ionization current based on a signal from the anode electrode, and switching control of a voltage supplied to the second cathode electrode A voltage switching control means for performing the operation, an output holding means for holding a current value from the first current measuring means at the time of voltage switching by the voltage switching control means, Outputs the calculation result as an instruction or outputs a signal to the outside in the form of a signal required from the outside such as an alarm signal. And an external output means having a function of controlling the unit.

Therefore, in the radiation detector according to the seventh aspect of the present invention, a transient output fluctuation that occurs when switching from a voltage causing gas multiplication to a voltage sufficient to collect 100% of generated electrons without gas multiplication occurs. Is not regarded as a change in the indicated value.

Further, according to the invention of claim 8, there are provided first and second cathode electrodes to which different voltages are applied, respectively, and an anode electrode, and at least one of the first and second cathode electrodes is provided at a position facing the first cathode electrode. A plurality of second cathode electrodes and anode electrodes are alternately arranged, and the first and second
Is divided into a plurality of blocks, and a signal from at least the anode electrode of the anode electrode or the first cathode electrode of each block is input, and the ionization current is measured based on the input signal. Measuring means for performing the following, a gate means provided on the input side of each signal to the signal measuring means, for opening and closing the input of the signal to the signal measuring means, and outputting a control signal for opening and closing each gate means Control means for performing a calculation by inputting a signal from the signal measurement means, outputting the calculation result as an instruction, or outputting a signal to an external device in a signal form required by the external device such as an alarm signal, and measuring the signal. A means for outputting to the control means a command to close one of the gate means when a signal from the means exceeds a predetermined output level. And an external output means having a.

Therefore, in the radiation detector according to the eighth aspect of the present invention, the effective volume of the detector main body is changed stepwise according to the radiation level, so that output saturation does not occur even when the radiation level is high. Thus, the output signal level can be reduced to an appropriate level.

Further, according to the ninth aspect of the present invention, there are provided first and second cathode electrodes to which different voltages are applied, respectively, and an anode electrode, and at least one of the first and second cathode electrodes is provided at a position facing the first cathode electrode. A plurality of second cathode electrodes and anode electrodes are alternately arranged, and the first and second cathode electrodes and anode electrodes are each divided into a plurality of blocks, and the anode electrode or the first electrode of each block is divided into a plurality of blocks.
A signal measuring means for inputting a signal from at least the anode electrode among the cathode electrodes and measuring the ionization current individually for each block based on the input signal; and applying the signal to the first and second cathode electrodes. The first and second cathode voltage adjusting means for individually controlling the voltage to be applied to each block, and a signal from each signal measuring means is inputted to perform an operation, and the operation result is output as an instruction or an alarm signal. Whether or not it is necessary to output a signal to the outside in a signal form required from the outside, and to reduce the voltage applied to the detector body based on the magnitude of the signal input from each signal measuring means. And an external output means having a function of outputting a control signal to the first and second cathode voltage adjusting means.

Therefore, in the radiation detector according to the ninth aspect of the present invention, an electrode group that is not operated can be formed by separately applying a voltage to the divided electrode groups.

According to a tenth aspect of the present invention, there are provided first and second cathode electrodes to which voltages different from each other are applied, and an anode electrode, and at least one of the first and second cathode electrodes is provided at a position facing the first cathode electrode. A plurality of second cathode electrodes and anode electrodes are alternately arranged, and the first and second cathode electrodes and anode electrodes are each divided into a plurality of blocks, and the anode electrode or the first electrode of each block is divided into a plurality of blocks.
A signal measuring means for inputting a signal from at least the anode electrode among the cathode electrodes and measuring an ionization current based on the input signal; and a signal measuring means provided on an input side of each signal to the signal measuring means. Gate means for opening and closing the input of a signal to the measuring means, control means for outputting a control signal for opening and closing each gate means, and voltage applied to each of the first and second cathode electrodes for each block. The first and second cathode voltage adjusting means, which individually control the signals, and a signal from the signal measuring means are input to perform an operation, and the operation result is output in the form of an instruction output or an externally required signal such as an alarm signal. Based on the function of outputting a signal to the outside and the magnitude of the signal input from the signal measuring means, it is determined whether or not it is necessary to reduce the voltage applied to the detector body. And a function of outputting a control signal to the second cathode voltage adjusting means, and issuing a command to close one of the gate means when a signal from the signal measuring means exceeds a predetermined output level. And external output means having a function of outputting to

Therefore, in the radiation detector according to the tenth aspect, the divided electrodes can be operated independently, and when the voltage applied to the second cathode electrode of an arbitrary divided electrode group is switched, By monitoring the outputs of the other electrode groups, it is possible to prevent missing measurements.

According to the eleventh aspect of the present invention, in the radiation detector according to the fourth aspect of the present invention, the third current measurement for measuring an ionization current based on a signal from the second cathode electrode or the anode electrode. Means for monitoring the gas growth gain in real time by comparing the current value from the second current measuring means with the current value from the third current measuring means to the external output means. Has been added.

Therefore, in the radiation detector according to the eleventh aspect of the invention, in addition to the operation of the radiation detector according to the fourth aspect of the invention, by comparing two measured values of the ionization current, the gas breeding gain can be adjusted in real time. Can be monitored.

According to a twelfth aspect of the present invention, in the radiation detector of the fifth aspect of the present invention, a voltage switching control means for switching and controlling a voltage supplied to the second cathode electrode is added, and a pulse output from the external output means is provided. When it is determined that the count is saturated, the voltage switching control unit controls the voltage applied to the second cathode electrode to decrease until the pulse count is no longer saturated.

Therefore, in the radiation detector according to the twelfth aspect, in addition to the operation of the radiation detector according to the fifth aspect, when the pulse count is saturated, the pulse count is not saturated. By reducing the high voltage applied to the second cathode electrode until then, it is possible to always maintain optimal gas growth without saturation.

According to a thirteenth aspect of the present invention, in the radiation detector according to any one of the first to twelfth aspects, the anode electrode is formed on the second cathode electrode surface by a fine processing technique. This is a cone-shaped electrode.

Therefore, in the radiation detector according to the thirteenth aspect of the present invention, the ratio of the area occupied by the second cathode electrode is almost 100%. The voltages applied to the two cathode electrodes can be the same.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention introduces a pulse counting method capable of accurately and stably measuring even lower levels of radiation, and by combining it with the above-mentioned conventional ionization current measurement, reduces the level of radiation from low radiation levels to high radiation levels. It is intended to perform accurate and stable measurement over a wide dynamic range up to.

Hereinafter, embodiments of the present invention based on the above-described concept will be described in detail with reference to the drawings. (First Embodiment) FIG. 1A is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment.

In FIG. 1A, a detector container 15 includes first and second cathode electrodes 11 and 12 and an anode electrode 13 to which different voltages are applied, respectively. At least one second cathode electrode 12 and a plurality of anode electrodes 13 are alternately arranged at a position facing 11.

An argon gas 16 as a detection gas for detecting radiation is hermetically sealed inside the detector container 15. Outside the detector container 15, a high voltage power supply 17 for the first cathode electrode 11, a high voltage power supply 18 for the second cathode electrode 12, and a pulse counting circuit 19
An external output circuit 110 is provided, and through the through-type current introduction terminal 14, each of the electrodes 11,
12 and 13 are connected.

In the radiation detector of the present embodiment configured as described above, for example, the electrode 12 is
Is maintained at a high potential, and the electrode 13 is further raised to a high potential so that a strong electric field is applied between the electrodes 12 and 13 to the extent that gas multiplication occurs.
The ionization signal of No. 6 is multiplied by gas and collected at the anode electrode 13.

The charge signal collected by the anode electrode 13 is supplied to the pulse counting circuit 19 through the through current terminal 14.
Supplied to The pulse counting circuit 19 includes a band-pass filter having a window of a frequency band determined by a detector shape and an applied voltage, an amplifier, and a peak-height discrimination circuit.

This pulse counting circuit 19 is provided, for example, in FIG.
As shown in (b), each time a pulse larger than the pulse height discrimination level is input, a pulse that can be detected by the external output circuit 110 is output.

The external output circuit 110 performs a counting operation by inputting a pulse from the pulse counting circuit 19,
The result is output to the outside in a signal form required from the outside such as an instruction output or an alarm signal.

In the above-described conventional radiation detector, the pulse width is several μs, whereas in the radiation detector of the present embodiment, the movement of electrons in the argon gas generated by gas breeding is caused by the electrode. Since there is only the gap between the electrode 12 and the electrode 13, the pulse width is as small as several tens ns. Therefore, it is possible to measure up to a relatively high counting rate.

That is, the first cathode electrode 11 and the second
The electrons generated in the argon gas 16 by the action of the electric field formed by the cathode electrode 12 and the anode electrode 13 drift to the vicinity of the second cathode electrode 12 or the anode electrode 13.

Then, energy is obtained from the high electric field formed by the second cathode electrode 12 and the anode electrode 13, and
This causes a so-called gas breeding, and this increased signal is collected on the anode electrode 13. At this time, since a short pulse signal appears in the signal measurement circuit, pulse counting can be performed.

As described above, in the radiation detector of the present embodiment, by employing the pulse counting method, it is possible to measure to a low radiation level which cannot be measured by the measurement of the ionization current. .

That is, assuming that 30 keV energy is given to the detection gas 16 by one radiation incident, the ionization current 10 pA output is about 50,000 cp.
s. In the pulse counting method, it is easy to count up to the order of 10 cps, so that the ionization current is 10 fA.
It is possible to measure up to a considerable radiation level. Further, since the pulse width is about 10 ns, measurement up to 10 Mcps is possible even in consideration of the random incidence of radiation. This corresponds to 2 nA.

Accordingly, if the range of measurement by ionization current is 1 Mcps or more and the range of measurement by pulse count is 1 Mcps or less, the radiation detector according to the present embodiment
The upper limit is 2 nA in ionization current, and the lower limit is 10 fA or less. This means that the measurement range of the conventional radiation detector is 11 pA to 74 mA, compared to 1000 pA.
It means that it is possible to measure up to 1 / radiation level.

(Second Embodiment) FIG. 2 is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment.
1A are denoted by the same reference numerals and description thereof is omitted, and only different portions will be described here.

In FIG. 2, a signal from the anode electrode 13 is inputted to a pulse counting circuit 19 and a current measuring circuit 22 via a frequency band filter circuit 21, and respective signals are inputted to an external output circuit 20. You.

Note that the frequency band filter circuit 21
Frequency band used by pulse counting circuit 19 and current measuring circuit 2
Since there are two pass bands of the two use frequency bands, the signal from the feedthrough current introduction terminal 14 is branched without interfering with each other.

The signal input to the pulse counting circuit 19 is subjected to the same processing as in the first embodiment. On the other hand, the signal input to the current measurement circuit 22 extracts a DC component and is detected as a current value.

The external output circuit 20 has a function of reading the output of the current measuring circuit 22 and performing the same calculation and external output as in the case of the external output circuit 110 of the first embodiment.

In the radiation detector of the present embodiment configured as described above, the output of the bandpass filter that allows a relatively high frequency band to pass is a pulse output of the signal collected by the anode electrode 13.

A bandpass filter that passes only a DC component corresponds to an integration circuit having a long time constant and outputs an ionization current. By simultaneously performing pulse counting and ionization current measurement on the output of the frequency band filter circuit 21, at a high radiation level where pulse counting cannot be performed in the first embodiment, radiation measurement is performed by ionization current. At low radiation levels, which are difficult to measure with ionization current, radiation can be measured by pulse counting.

That is, by separating the pulse component and the current component by the operation of the frequency band filter circuit 21 provided at the input stage of the signal measuring circuit, not only pulse counting but also current measurement can be performed.

As described above, the radiation detector according to the present embodiment can measure up to a higher radiation level than the first embodiment. (Third Embodiment) FIG. 3A is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment, and the same parts as those in FIG. Here, only the different parts will be described.

In FIG. 3A, in place of the pulse counting circuit 19 in the second embodiment, in addition to the function of the pulse counting circuit 19, a function of separately outputting a signal before wave height discrimination is provided. The pulse count circuit 33 is further provided with a signal before the pulse height discrimination from the pulse count circuit 33, and the current value (ionization current) from the through current introduction terminal 14 is determined based on the pulse wave height and the pulse arrival frequency.
Is provided.

The external output circuit 32 receives the current value signal reconstructed by the circuit 31 for reconstructing the ionization current in addition to the function of the external output circuit 20 in the second embodiment, and performs the current measurement. A function of comparing with a signal from the circuit 22;

For example, the signals of the pulse counting circuit 33 and the current measuring circuit 22 become, for example, as shown in FIG. 3B as the signal from the through current introducing terminal 14 increases. This is because when the signal from the through current introduction terminal 14 exceeds a certain level, the signal of the pulse counting circuit 33 piles up, and the frequency of counted pulses becomes smaller than the actual frequency. Also, the pulse crest value is not exactly proportional to the generated charge amount (mainly the pulse crest is reduced).
That's why.

In the radiation detector of the present embodiment configured as described above, when the pulse measurement reaches the limit, the ionization current is directly measured from the signal of the anode electrode 13 and the ionization current is determined from the pulse measurement result. Since there is a discrepancy with the result of reconstructing, the upper limit of the radiation level to which the pulse counting method limited by the saturation of the pulse counting can be applied can be known.

That is, by the action of the frequency band filter circuit 21 provided at the input stage of the signal measuring circuit, the pulse component and the current component are separated to perform pulse counting and current measurement.
And reconstruct the current output from the pulse count frequency and peak value,
The upper limit of the pulse countable area can be known.

As described above, the radiation detector according to the present embodiment makes it possible to know the upper limit of the pulse countable area as compared with the second embodiment. (Fourth Embodiment) FIG. 4 is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment. The same parts as those in FIG. Here, only the different parts will be described.

In FIG. 4, the first cathode electrode 11
A current measuring circuit 41 is provided in series with the high-voltage power supply 17. The anode electrode 13 has a pulse counting circuit 1
9 is connected. Each signal is output to the external output circuit 4
2 is connected.

In the radiation detector of the present embodiment, the operation of the pulse counting is the same as that of the pulse counting circuit 19 of the first embodiment. on the other hand,
The current measurement from the first cathode electrode 11 is performed by the current measurement circuit 41. This current measuring circuit 41 operates in the same manner as the current measuring circuit 22 of the second embodiment, except that the signal current from the second cathode electrode 12 corresponds to the signal from the first cathode electrode 11. Since the current is about 1/100, the current measuring circuit 41 uses a circuit more suitable for measuring a very small current than the current measuring circuit 22.

The external output circuit 42 operates basically in the same manner as the external output circuit 20 of the second embodiment, and calculates the output of the current measuring circuit 41. Different conversion factors for quantity.

That is, by connecting the pulse counting circuit 19 to the anode electrode 13, the number of pulses can be counted. Further, by connecting the current measuring circuit 41 to the first cathode electrode 11, the ionization current due to argon ions, which is not affected by the electron multiplication between the second cathode electrode 12 and the anode electrode 13, can be measured.

As described above, the radiation detector of this embodiment is different from the first embodiment in that the pulse is measured by the signal from the anode electrode 13 at a low radiation level, and the pulse is measured at a high radiation level. By performing ionization current measurement using a signal from one cathode electrode 11, the dynamic range of measurement can be expanded to the maximum.

(Modification of the Fourth Embodiment) In the present embodiment, the current measuring circuit 4 connected to the first cathode electrode 11 in the radiation detector of the fourth embodiment is different from that of the fourth embodiment.
In addition to the above, a configuration is adopted in which separate current measuring circuits are connected to the second cathode electrode 12 or the anode electrode 13 to measure the ionization current.

In the radiation detector of the present embodiment configured as described above, the pulse
In addition to performing the same operation as in the embodiment, the gas growth gain can be monitored in real time by comparing the two measured ionization current values.

That is, by comparing the two measured values of the ionization current, the gas growth gain can be monitored in real time. As described above, in the radiation detector of the present embodiment, the gas breeding gain can be monitored in real time as compared with the first embodiment,
It is possible to check the soundness of the radiation detector during operation of the radiation detector.

Further, the gas breeding gain of the pulse circuit system does not need to be known in advance by calibration, and the system configuration can be simplified. (Fifth Embodiment) FIG. 5 is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment. The same parts as those in FIG. Here, only the different parts will be described.

In FIG. 5, the second cathode high voltage power supply 18 for supplying a high voltage to the second cathode electrode 12 is provided with a voltage switching controller 51.
A signal from the anode electrode 13 is supplied to the through current introduction terminal 1.
4, the signal is branched by the frequency band filter circuit 21.
The pulse signal is input to the pulse counting circuit 33, and the current signal is input to the current measuring circuit 22. The processing in these circuits is the same as that in the third embodiment.

On the other hand, the signal from the first cathode electrode 11 is input to the current measuring circuit 41, and the output is input to the external output circuit 52. In the external output circuit 52, the pulse output from the pulse counting circuit 33, the current measurement circuit 2
2. a current measurement value from the circuit 31 for reconstructing the ionization current;
Receiving each signal output of the current measurement value from the current measurement circuit 41, the following calculation is performed.

(A) Conversion of the pulse count rate from the pulse counting circuit 33 to a signal required from the outside such as a radiation level. (B) Reading of a reconstructed current value from the circuit 31 for reconstructing the ionization current. (C) Reading of the current value from the current measurement circuit 22 (d) Confirmation of saturation as in the case of the third embodiment (e) Applied voltage of the second cathode high-voltage power supply 18 and gas growth rate ( = Calculation and storage of the relationship of (current value from current measurement circuit 22 / current measurement value from current measurement circuit 41) (f) Pulse counting circuit 33 mediated by a signal from circuit 31 for reconstructing ionization current, current Confirmation that there is no pile-up by confirming the proportional relationship of each output from the measurement circuit 22 and the current measurement circuit 41, and conversion into radiation dose In the radiation detector of the present embodiment configured as described above, gas The relationship between the amount of charge and the amount of radiation occurs,
The signal from the first cathode electrode 11 which is not affected by the gas multiplication is used as a reference.

In this embodiment, in the external output circuit 52, the pulse counting circuit 3 for the signal from the anode electrode 13 is used.
3 and the current measuring circuit 22, and the current measuring circuit 41 and the anode electrode 1 of the signal from the first cathode electrode 11.
The proportionality of the current measurement circuit 22 for the signals from 3 is calibrated.

As described above, the output level is corrected in the external output circuit 52 using the relationship between the high voltage value and the gas breeding gain stored in advance. That is, the relationship between the voltage applied to the second cathode electrode 12 and the gas multiplication rate is determined by a calibration test, and the result is stored in an appropriate storage unit (external output circuit 52) in the signal measurement circuit.
By reading the result at the time of signal measurement and dividing the ionization current calculated from the pulse height and the count rate by the gas growth rate, the current obtained at the first cathode electrode 11 is obtained by calculation. By comparing with the result obtained by the current measuring circuit 22 actually connected to the first cathode electrode 11, the radiation level can be monitored while confirming that the pulse count is not saturated.

Therefore, since the signals from the pulse counting circuit 33 and the current measuring circuit 22 are calibrated with reference to the signal from the current measuring circuit 41, the radiation detector can have a wide dynamic range.

As described above, the radiation detector of this embodiment differs from the radiation detector of the third embodiment in that the signal increases when the radiation level becomes high while the gas breeding is maintained. Since the upper limit of the dynamic range is too short, it is possible to limit the output to an appropriate value by lowering the applied voltage.

In addition, it is possible to confirm that the saturation of the pulse count has not occurred at the same time as the radiation measurement. (Modification of Fifth Embodiment) In the present embodiment, in the radiation detector of the fifth embodiment, the external output circuit 52 includes a circuit 31 for reconstructing an ionization current or a current measurement circuit 22. Outputs an alarm signal indicating that the current measuring circuit 41 is saturated to the voltage switching controller 51, and the voltage switching controller 51 lowers the high voltage applied voltage until the alarm signal disappears. By adding a function of controlling the high voltage power supply 18 for the cathode, it is possible to always maintain optimal gas growth without saturation.

That is, when the pulse count is saturated, by reducing the high voltage applied to the second cathode electrode 12 until the pulse count is no longer saturated, it is possible to always maintain the optimum gas growth without saturation. it can.

(Sixth Embodiment) FIG. 6 is a schematic diagram showing an example of a radiation detector according to the present embodiment.
1A are denoted by the same reference numerals and description thereof is omitted, and only different portions will be described here.

In FIG. 6, a signal from the anode electrode 13 is passed through a through current introduction terminal 14 to a frequency bandpass filter 61 having a window whose frequency band is adjusted to the RMS voltage and a window whose frequency band is adjusted to pulse measurement. Input, and its output is supplied to the pulse counting circuit 19 and the RM
It is supplied to an S (Root Mean Square) voltage measuring circuit 62.

Outputs from the pulse counting circuit 19 and the RMS voltage measuring circuit 62 are supplied to an external output circuit 63. The first cathode electrode 11 includes a current measuring circuit 41
Connected to.

In the radiation detector of the present embodiment configured as described above, for pulse counting, the frequency band filter 61 has a window between the frequency band of pulse counting and the frequency (DC) of current measurement. Have. The intermediate frequency coincides with the measurement frequency band of the RMS voltage circuit 62.

The RMS voltage measuring circuit 62 measures the effective voltage of the signal that has passed through the frequency band filter 61 and outputs it to the external output circuit 63. The external output circuit 63 receives the pulse count output from the pulse count circuit 19 and the RMS voltage output from the RMS voltage measurement circuit 62, and performs externally required arithmetic processing such as conversion to a radiation level.

Thus, pulse counting and RMS voltage measurement are performed on the signal from anode electrode 13. On the other hand, a signal from the first cathode electrode 11 is input to a current measuring circuit 41 to measure a current.

That is, by the action of the frequency bandpass filter at the input stage of the signal measurement circuit from the second cathode electrode 12, the frequency band in which an RMS voltage output proportional to the radiation signal is obtained and the frequency bandpass filter 61 capable of pulse counting. Is provided, not only pulse measurement and RMS voltage measurement from the anode electrode 13 but also ionization current measurement from the first cathode electrode 11 can be performed.

As described above, in the radiation detector of the present embodiment, compared to the first embodiment, the accuracy is increased by pulse counting at a low radiation level, the accuracy is low in current measurement, and the accuracy is low in pulse measurement. Even when there is a high radiation level that makes measurement difficult, it is possible to monitor the radiation level with high accuracy by measuring the RMS voltage.

Also, in the external output circuit 63, a smooth transition between the two measurement methods can be achieved by taking a weighted average of the ionization current signal from the first cathode electrode 11 and the RMS voltage signal from the anode electrode 13. It becomes possible.

(Seventh Embodiment) FIG. 7A is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment, and the same parts as those in FIG. The description thereof is omitted, and only different portions will be described here.

In FIG. 7A, a voltage switching controller 51 for adjusting the switching of the voltage of the second cathode electrode 12 and an output holding circuit 72 for holding the output of the anode electrode 13 during the transition of the switching are provided. I have.

Further, in order to control the voltage switching controller 51 and the output hold circuit 72, in addition to the function of the external output circuit 110 of the first embodiment, an external control circuit having a function of controlling the voltage switching controller 51 is added. An output circuit 73 is provided.

In the radiation detector of the present embodiment configured as described above, the function of the output hold circuit 72 inhibits the transient signal change occurring when the second cathode high voltage power supply 18 is switched. .

In this case, the timing at which the output hold circuit 72 holds the signal is, for example, the timing as shown in FIG. In addition, there is a method of monitoring the fluctuation of the signal and holding the fluctuation until the fluctuation with time becomes smaller than a certain value.

That is, the transient output fluctuation that occurs when switching from the voltage causing gas multiplication to a voltage sufficient to collect 100% of the generated electrons without gas multiplication occurs.
The change in the indicated value can be prevented.

As described above, the radiation detector of the present embodiment is different from the first embodiment in that the change in signal that occurs during the transition from the state in which gas multiplication occurs to the ionization chamber saturation state is described. Can be prevented from being output to the outside.

(Eighth Embodiment) FIG. 8 is a schematic configuration diagram showing an example of a radiation detector according to the present embodiment.
1A are denoted by the same reference numerals and description thereof is omitted, and only different portions will be described here.

In FIG. 8, each of the electrodes 11, 12, and 13 is divided into a plurality of blocks, and a signal from each block is input to a signal measuring circuit 82 via a gate circuit 81. The gate circuit 81 is connected to the controller 83, and its control state is input to the external output circuit 84.

The external output circuit 84 stores a predetermined output level in order to adjust the detection sensitivity according to the amount of incident radiation. When a signal from a signal measurement circuit (which may be any one of the above-described pulse measurement, RMS measurement, and current measurement, or a combination thereof) exceeds a predetermined level, the controller 83 The controller 83 outputs a command to close any one of the gates, and the controller 83 outputs a signal for closing any one of the gates.

In the radiation detector of the present embodiment configured as described above, which arbitrary block of the electrodes is connected is selected, and the content is sent to the external output circuit 84, where the detection sensitivity is determined. Used as a correction.

That is, by gradually changing the effective volume of the detector main body in accordance with the radiation level, the output signal level is reduced to an appropriate level so that output saturation does not occur even when the radiation level is high. can do.

As described above, the radiation detector of the present embodiment differs from the first embodiment in that the signal from the radiation detector having a large gain due to gas multiplication is a normal signal. Since the output signal is larger than the output signal in the ionization chamber state, the signal becomes excessive when the radiation level becomes high. Therefore, by lowering the detection sensitivity by dividing the electrode groups, it is possible to keep the output within an appropriate output range.

(Modification of Eighth Embodiment) In the radiation detector of the eighth embodiment, the first high-voltage power supply for cathode 1 for applying a voltage to the first cathode electrode 11
7, a gate circuit 81 similar to the above may be provided also for a current signal from a current measuring circuit 41 for measuring an ionization current. Can be obtained.

(Ninth Embodiment) FIG. 9 is a schematic diagram showing an example of a radiation detector according to the present embodiment.
The same parts as those in FIG. 8 are denoted by the same reference numerals, and the description thereof will be omitted. Only different parts will be described here.

In FIG. 9, high-voltage power supply voltage supplied to first cathode electrode 11 and second cathode electrode 12 by controlling first cathode high voltage power supply 17 and second cathode high voltage power supply 18 is shown. Control the first,
Second cathode voltage adjusting circuits 91 and 92 are provided.

The outputs of the first and second cathode voltage adjusting circuits 91 and 92 are supplied to an external output circuit 93.
Outputs the voltage status. Further, a signal from the anode electrode 13 is supplied to an external output circuit 93 via a signal measurement circuit 82.

That is, the signals from the anode electrode 13 are input to the signal measuring circuit 82 and are processed by the external output circuit 93. In the external output circuit 93, in addition to calculations according to external requests, such as conversion to radiation levels,
Based on the magnitude of the signal input to the external output circuit 93, it is determined that it is necessary to reduce the voltage applied to the detector, and a control signal is output to the first and second cathode voltage adjustment circuits 91 and 92.

It should be noted that a configuration may be adopted in which the same processing is performed by monitoring not only the signal from the anode electrode 13 but also the signal from the second cathode electrode 12.

In the radiation detector of the present embodiment configured as described above, the cathode voltage can be adjusted for each electrode block. That is, by separately applying a voltage to the divided electrode groups, an electrode group that is not operated can be formed.

As described above, the radiation detector according to the present embodiment is different from the eighth embodiment in that the operation and non-operation are controlled for each electrode block so that the radiation level is high and the detection sensitivity is high. If there is room, the number of electrode blocks to be deactivated is increased, the analysis of the quenching gas mixed in the detection gas 16 is reduced, and the life of the detector can be extended.

(Tenth Embodiment) FIG. 10 is a schematic diagram showing an example of a radiation detector according to the present embodiment. The same parts as those in FIG. Here, only the different parts will be described.

In FIG. 10, in addition to the ninth embodiment of FIG. 9, the anode electrode 13 from each electrode block is provided.
, A gate circuit 81 for the signal from. Also,
As the external output circuit 101, a circuit obtained by adding a control function of the controller 83 to the external output circuit 93 is used.

In the radiation detector of the present embodiment configured as described above, the divided electrodes can be operated independently, and the voltage applied to the second cathode electrode 12 of an arbitrary divided electrode group can be controlled. By monitoring the outputs of the other electrode groups at the time of switching, it is possible to prevent missing from occurring.

That is, the divided electrodes can be operated independently, and when the voltage applied to the second cathode electrode 12 of an arbitrary divided electrode group is switched, the outputs of the other electrode groups are monitored. As a result, missing data can be prevented from occurring.

As described above, the radiation detector of this embodiment is different from the ninth embodiment in that an independent detector is housed in the same detector container, Even when the supply of high voltage to the detector changes, it is possible to eliminate missing time by detecting signals from other electrode blocks.

(Eleventh Embodiment) FIG. 11 is a schematic configuration diagram showing a characteristic portion of a radiation detector according to the present embodiment. The same portions as those in FIG. A description thereof is omitted, and only different portions will be described here.

In FIG. 11, the second cathode electrode 12
On the surface, the anode electrode 13 is configured by a fine processing technique such that the diameter and the mounting pitch of the anode electrode 13 are approximately the same.

That is, the anode electrode 13 is a cone-shaped electrode formed on the surface of the second cathode electrode 12 by a fine processing technique. In the radiation detector of the present embodiment configured as described above, it is possible to improve the uniformity of the radiation detection sensitivity of the surface on which the anode electrode 13 and the second cathode electrode 12 are formed by the fine processing technique. it can.

That is, since the ratio of the area occupied by the second cathode electrode 12 is almost 100%, the voltage applied to the anode electrode 13 and the voltage applied to the second cathode electrode 12 are the same at a voltage that does not cause gas multiplication. Can be

As described above, in the radiation detector according to the present embodiment, the anode electrode 13 is disposed closer to the second cathode electrode 12 than in the first embodiment, and is uniformly disposed. Thus, it is possible to reduce the difference in the gas multiplication gain depending on the incident position of the radiation and to improve the uniformity of the radiation detection sensitivity. Therefore, it can be applied to an extremely small detector.

[0123]

As described above, according to the radiation detector of the present invention, the measurement lower limit level of the detector is lowered to accurately and stably measure a wide dynamic range from a low radiation level to a high radiation level. Can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a radiation detector according to the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the radiation detector according to the present invention.

FIG. 3 is a schematic configuration diagram showing a third embodiment of the radiation detector according to the present invention.

FIG. 4 is a schematic configuration diagram showing a fourth embodiment of the radiation detector according to the present invention.

FIG. 5 is a schematic configuration diagram showing a fifth embodiment of the radiation detector according to the present invention.

FIG. 6 is a schematic configuration diagram showing a sixth embodiment of the radiation detector according to the present invention.

FIG. 7 is a schematic configuration diagram showing a radiation detector according to a seventh embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing an eighth embodiment of the radiation detector according to the present invention.

FIG. 9 is a schematic configuration diagram showing a ninth embodiment of the radiation detector according to the present invention.

FIG. 10 is a schematic configuration diagram showing a radiation detector according to a tenth embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing an eleventh embodiment of the radiation detector according to the present invention.

FIG. 12 is a schematic configuration diagram showing an example of a conventional ionization chamber type radiation detector.

[Explanation of symbols]

11: first cathode electrode, 12: second cathode electrode, 13: anode electrode, 14: through-type current introduction terminal, 15: detector container, 16: detection gas (argon gas), 17: first cathode High voltage power supply for 18; second high voltage power supply for cathode; 19, 33 pulse counting circuit 20, 32, 42, 63, 52, 73, 84, 93, 1
01, 110: external output circuit, 21: frequency band filter circuit, 22, 41: current measuring circuit, 31: circuit for reconstructing ionization current, 51: voltage switching controller, 61: frequency band filter, 62: RMS voltage measurement Circuit: 72 Output hold circuit 81: Gate circuit 82: Signal measurement circuit 83: Controller 91: First cathode voltage adjustment circuit 92: Second cathode voltage adjustment circuit 111: Electrode by fine processing

Claims (13)

[Claims] 1. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the plurality of anode electrodes are alternately arranged at a position facing the first cathode electrode, and a signal from the anode electrode is provided. As an input, a pulse counting means for outputting a pulse each time a signal greater than a predetermined pulse height discrimination level is input, performing a calculation by inputting a pulse from the pulse counting means, and outputting the calculation result as an instruction, Alternatively, an external output means having a function of outputting a signal to the outside in a signal form required from the outside such as an alarm signal, and a radiation detector. 2. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the plurality of anode electrodes are alternately arranged at a position facing the first cathode electrode, and a signal from the anode electrode is provided. Frequency band filter means for inputting and branching the input signal into a signal of a frequency band for pulse counting and a signal of a frequency band for current measurement, and a signal of a frequency band for pulse counting from the frequency band filter means. Pulse counting means for outputting a pulse each time a signal larger than a predetermined wave height discrimination level is input, and a signal in a frequency band for current measurement from the frequency band filter means as an input, and a DC component is input. A first current measuring means for taking out and detecting as a current value (ionization current); a pulse from the pulse counting means; And a function of inputting a current value from the first current measuring means and performing a calculation, outputting the calculation result as an instruction, or outputting a signal to the outside in a signal form required from the outside such as an alarm signal. A radiation detector, comprising: external output means; 3. The radiation detector according to claim 1, wherein a signal of a frequency band for pulse counting from the frequency band filter means is input instead of the pulse counting means, and a predetermined wave height discrimination is performed. Each time a signal greater than the level is input, a pulse is output, and a pulse counting means for separately outputting a signal before pulse height discrimination is provided.Further, a signal before pulse height discrimination from the pulse counting means is input, and A radiation detector comprising a means for reconstructing a current value (ionization current) based on a signal from the anode electrode based on a pulse wave height and a pulse arrival frequency. 4. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the anode electrode are alternately arranged at a position facing the first cathode electrode; A second current measuring means for measuring an ionization current based on the signal of the above, and a pulse which receives a signal from the anode electrode and outputs a pulse every time a signal larger than a predetermined wave height discrimination level is inputted. A counting unit, a pulse from the pulse counting unit, and a current value from the second current measuring unit are input to perform a calculation, and the calculation result is output as an instruction or a signal form required from the outside such as an alarm signal An external output means having a function of outputting a signal to the outside with the radiation detector. 5. The radiation detector according to claim 3, further comprising second current measuring means for measuring an ionization current based on a signal from the first cathode electrode, and further comprising the external output. In the means, the relationship between the voltage applied to the second cathode electrode and the gas growth rate stored in advance, the pulse from the pulse counting means, the current value from the means for reconstructing the current value, A radiation detector for determining whether or not the pulse count is saturated based on the respective current values from the first and second current measuring means. . 6. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the anode electrode are alternately arranged at a position facing the first cathode electrode, and a signal from the anode electrode is provided. Frequency band filter means for inputting and branching the input signal into a signal of a frequency band for pulse counting and a signal of a frequency band for current measurement, and a signal of a frequency band for pulse counting from the frequency band filter means. Pulse counting means for outputting a pulse each time a signal greater than a predetermined pulse height discrimination level is input, and a signal in a frequency band for current measurement from the frequency band filter means as an input, and the input signal Effective voltage (R
An effective voltage measuring means for measuring and outputting an RMS voltage as an RMS voltage; inputting a pulse from the pulse counting means and an RMS voltage from the effective voltage measuring means to perform an operation; Alternatively, an external output means having a function of outputting a signal to the outside in a signal form required from the outside such as an alarm signal, and a radiation detector. 7. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, and a plurality of at least one of the second cathode electrode and the anode electrode are alternately arranged at a position facing the first cathode electrode, and a signal from the anode electrode is provided. A first current measuring means for measuring an ionization current based on the voltage; a voltage switching control means for switching and controlling a voltage supplied to the second cathode electrode; An output holding means for holding a current value from the current measuring means, and a calculation performed by inputting the hold value from the output holding means, and outputting the calculation result in an instruction output or a signal form required from the outside such as an alarm signal. External output means having a function of outputting a signal to the outside and controlling the voltage switching control means, Radiation detector according to claim Rukoto. 8. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the plurality of anode electrodes are alternately arranged at a position facing the first cathode electrode; The cathode electrode and the anode electrode are each divided into a plurality of blocks, and a signal from at least the anode electrode of the anode electrode or the first cathode electrode of each block is input, and an ionization current of ionization current is determined based on the input signal. Signal measuring means for performing measurement; gate means provided on the input side of each signal to the signal measuring means for opening and closing the input of a signal to the signal measuring means; control for opening and closing each of the gate means A control unit for outputting a signal, and performing a calculation by inputting a signal from the signal measuring unit;
Instructing the calculation result, or outputting a signal to the outside in a signal form required from the outside such as an alarm signal, and when a signal from the signal measuring means exceeds a predetermined output level, An external output unit having a function of outputting a command to close any one of the gate units to the control unit. 9. An ionization chamber type radiation detector for detecting radiation by measuring the ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the plurality of anode electrodes are alternately arranged at a position facing the first cathode electrode; The cathode electrode and the anode electrode are each divided into a plurality of blocks, and a signal from at least the anode electrode of the anode electrode or the first cathode electrode of each block is input, and each of the blocks is based on the input signal. A signal measuring means for individually measuring an ionization current for each of the first and second cathode electrodes; Means for inputting a signal from each of the signal measuring means to perform an operation, and outputting the operation result as an instruction or an external signal such as an alarm signal. In addition to performing signal output to the outside in the form of a signal to be determined, it is determined whether or not it is necessary to reduce the voltage applied to the detector body based on the magnitude of the signal input from each of the signal measuring means. And an external output unit having a function of outputting a control signal to the first and second cathode voltage adjusting units. 10. An ionization chamber type radiation detector for detecting radiation by measuring an ionization current due to the incidence of radiation by applying the measurement principle of the ionization chamber. Second
A cathode electrode and an anode electrode, at least one of the second cathode electrode and the plurality of anode electrodes are alternately arranged at a position facing the first cathode electrode; The cathode electrode and the anode electrode are each divided into a plurality of blocks, and a signal from at least the anode electrode of the anode electrode or the first cathode electrode of each block is input, and an ionization current of ionization current is determined based on the input signal. Signal measuring means for performing measurement; gate means provided on the input side of each signal to the signal measuring means for opening and closing the input of a signal to the signal measuring means; control for opening and closing each of the gate means A control unit for outputting a signal; and a voltage applied to each of the first and second cathode electrodes are individually controlled for each of the blocks. First and second cathode voltage adjusting means performs arithmetic operations by using signals input from the signal measurement means,
The function of outputting the calculation result as an instruction or a signal output to the outside in the form of a signal required from the outside such as an alarm signal, based on the magnitude of the signal input from the signal measuring means, to the detector main body. A function of determining whether it is necessary to reduce the applied voltage and outputting a control signal to the first and second cathode voltage adjusting means, and a signal from the signal measuring means exceeding a predetermined output level. And an external output unit having a function of outputting a command to close one of the gate units to the control unit in the case of a radiation detector. 11. The radiation detector according to claim 4, further comprising a third current measuring means for measuring an ionization current based on a signal from the second cathode electrode or the anode electrode, Further, a function of monitoring the gas growth gain in real time by comparing the current value from the second current measuring means with the current value from the third current measuring means is added to the external output means. A radiation detector, comprising: 12. The radiation detector according to claim 5, further comprising: voltage switching control means for switching and controlling a voltage supplied to the second cathode electrode, wherein a pulse count is saturated by the external output means. If it is determined that there is a radiation detector, the voltage switching control means controls the voltage applied to the second cathode electrode to decrease until the pulse count is no longer saturated. 13. The radiation detector according to claim 1, wherein the anode electrode includes a cone-shaped electrode formed on a second cathode electrode surface by a fine processing technique. A radiation detector characterized in that: