JPH03211487A - Ionizing box type radiation detecting device - Google Patents

Abstract

PURPOSE:To improve the detection reliability by inputting an ionizing current to a 2nd amplifying circuit when an irradiation dosage rate exceeds a specific value, and sending the output of the 2nd amplifying circuit as a radiation detection signal. CONSTITUTION:When the dosage rate I is large and the value of a signal 17a is larger than S, a switching signal 18a goes up to an H level in this radiation detecting device 20. Then the ionizing current 2a is converted by the amplifying circuit 16 into a voltage, which is amplified and outputted as the detection signal 17a from a switch 17. In this case, the ionizing current 2a is converted into a voltage signal 12a by an initial-stage amplifying element 12b which employs a junction type FET, so the irradiation dosage rate detection error of the detection signal 17a becomes slightly large, but the characteristics of an amplifying element 12b vary owing to large irradiation dosage irradiation with radiation 3, so that the dosage rate detection is never disabled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an ionization chamber and an ionization current output from the ionization chamber.
An ionization chamber-type radiation detection device in which an ionization chamber and an amplifier circuit are integrated, such as a case where an amplifier circuit for converting and amplifying the ionization chamber is housed in the same housing, especially for radiation irradiation dose a This relates to a device with a highly reliable detection function for #c.

[Conventional technology]

The gourd box type radiation detection device is 5K as mentioned above.

Generally, there is an ionization chamber that detects radiation such as R-rays and outputs an ionization current according to the irradiation dose rate of this radiation, and a multistage voltage amplification circuit that converts the ionization current into voltage and amplifies this voltage. It consists of.

The voltage signal output from this amplifier circuit
The JIIsI rate is set to Yokota, but in this case,
44 for long ionization current transmission between the i and ionization chamber voltage amplification circuits by separating them! i! When connected with
There is a risk that large irradiation dose rate detection errors may occur due to internal noise generated due to electrostrictive phenomena in the conductor due to the eel and noise entering from outside the conductor 41K. The box and the multistage voltage amplification circuit are housed in a single housing to shorten the length of the conductor. A so-called ionization chamber/amplification circuit integrated separation chamber type radiation detection apparatus l shown in FIG. 2 may be employed.

In Fig. 2, 2 is an ionization box that detects radiation 3 such as gamma rays and outputs an ionizing current 2a according to the irradiation dose rate of the radiation 3, and 4 is a W current 2a when ionization R2a is input.
Converts the signal into a voltage and outputs the voltage signal 4a corresponding to the converted voltage (E). When the signal 4a is input, 5 amplifies this signal 4a and outputs a voltage signal according to the result. A radiation detection signal 5a is output as a radiation detection signal 5a.A rear-stage amplifier is composed of at least one voltage amplifier, and 6 is a multistage amplification circuit consisting of amplifiers 4 and 5.7 is an ionization chamber 2
0 There is a direct current high force at the Yin-Yang and Yang-yi Polar Gates, which are not shown in the diagram.

A high-voltage power supply line 8 is designed to apply a voltage to a multi-stage amplifier circuit 6VC, and 5 supplies a direct current low power source as a t source of the circuit.
The low-voltage power supply line 9 is a housing housing the ionization fi 2 and the amplifier circuit 6, and the radiation detection device 1 is composed of the above-mentioned parts. And then again.

In the radiation detection device 1, since the ionizing current 2a is a minute current, a MOS type FET having a high input impedance is used as the amplification element 4b constituting the first stage amplifier 4.

[Problem to be solved by the invention]

Each part of the radiation detection signal equipment is constructed as described above, and the conducting wire between the ionization chamber 2 and the amplifier circuit 6 is very short, and the amplifier element 4b is a MOS type IT having a high input impedance. Therefore, it is clear that the radiation detection equipment has a small irradiation dose rate detection error. If the radiation becomes extremely large due to In this case, the MOS type F E 1' as the element 4b has a characteristic that when exposed to radiation 3 with a large irradiation rate 1 for a long time (l?, t), an extremely large 4? change occurs. Therefore, there is a possibility that the detection of the Terumura amount rate by the radiation detection device 1 will be incorrect.

The detection device fIK has one point in that it has a lower iH axis degree of dose rate detection than the field rate.

The purpose of the present invention is to maintain the radiation dose rate detection function of the radiation dose rate 41 even if irradiated with radiation with a large radiation filling rate for a long time. To obtain an ionization chamber-type radiation detection device that is integrated with an ionization chamber and an amplifier circuit and has a high i-rate detection reliability IW.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an ionization chamber that detects radiation 4I and outputs an ionization current according to the detection result, and a multistage amplifier circuit that employs a MOS type F'ET as a first stage amplifier element. and a first amplifier circuit.

A second amplifier circuit as a multi-stage amplifier circuit employing a junction type FET as a first-stage multiplication element; ! ! a 'lL1 signal generator input to the width circuit; a second signal generator that switches each output signal of the two amplifier circuits according to the input Kiriyanagi signal and outputs it as a radiation detection signal; and the radiation@detection signal. An ionization chamber type radiation IN@ detection device that is integrally provided with a signal level discrimination circuit that outputs the switching signal according to the value of the signal, and detects the irradiation dose rate of the radiation based on the radiation detection signal, When the irradiation dose rate represented by the radiation detection signal is small, the two switchers and the KtI signal level discrimination circuit 121 input the distant lightning, R, to the first amplifier circuit, and also input the R to the first amplifier circuit. outputs an output signal as the radiation detection signal, and when the irradiation dose rate represented by the radiation detection signal becomes equal to or higher than a predetermined value, inputs the ionizing current to the second amplifier circuit and outputs the second amplifier circuit. The ionization chamber type radiation detection device is configured to output the signal as the radiation detection signal.

[Effect]

When the VC is configured as shown below, the tram box, both amplifier circuits, both disconnectors, and signal level TP separate circuits are integrated, so the length of the conductor between the ionization chamber and both amplifier circuits can be shortened. Therefore, in terms of the noise generated in the conducting wire, it is possible to obtain an intoxication box type radiation detection device with a small irradiation dose rate detection error, similar to the radiation detection device 6M1 described above. Furthermore, when configured as shown in 8C above, when the irradiation dose rate of radiation is small and therefore the value of the ionizing current is small, a radiation detection signal corresponding to the ionizing iE current is output as the output signal of the first amplifier circuit. However, this first
Since the first-stage amplification element of the amplifier circuit uses a MOS type FET with low human impedance, the current is small (even at ℃). Then, if you configure it as above,

The irradiation dose rate of radiation exceeds a predetermined value, and therefore v
When the L ionization current value is large and there is a risk of causing a characteristic change in the MOS FET described above, a radiation detection signal corresponding to the ionization current is output from the second switch as an output signal of the second amplifier circuit. However, the input impedance of the first stage amplifying element VC of this second amplifying circuit is the same as that of the above-mentioned MOS.
Although the junction type FIT is lower than the type FET, it is less likely to cause changes in characteristics due to radiation irradiation at a large dose. Although the irradiation dose rate detection at is slightly reduced compared to the case where it is less than the predetermined value, a situation in which the detection of the chain dose rate becomes impossible does not occur.

Therefore, with the above configuration, radiation irradiation-I
An ionization chamber type radiation detection device with high detection reliability with respect to radiation rate can be obtained.

〔Example〕

FIG. 1 is a block diagram of one embodiment of the present invention. In this figure, the same parts as in FIG. 2 are given the same reference numerals as in FIG. 2.

In the VC of FIG. 1, 10 is a switching signal 18a as an input binary signal. When the power level is L level, wLw71
The ionization current 2a output from the box 2 is input to the first stage amplifier 111C, and when the level of the signal 18a is H level, the ionization current 2a is input to the first stage amplifier 12. A MOS type FET is adopted as the first-stage amplifying element 11b as an amplifying element constituting this amplifier 11, and operates in the same manner as the first-stage amplifier 4 described above to correspond to the voltage signal 4a. Voltage signal 11 representing ionizing current 2a
Further, the amplifier 12 has a junction type FgT adopted as the first stage amplifying element 12F) as an amplifying element constituting this amplifier 12, and operates in the same manner as the amplifier 4 described above. This corresponded to the heavy pressure signal 43. ?
! It is configured to output a voltage signal 12a representing a separation current 2atf. 13 amplifies the signal 11a when it is input, and generates a corresponding voltage signal t3a as a result.
Output. f! consists of at least one voltage amplifier. A stage amplifier 14 amplifies the signal 12a when the signal 12a is input, and generates a voltage signal 14a according to the result.
Output. 15 is a first amplifier circuit as a multi-stage amplifier circuit consisting of amplifiers 11 and 13, and 16 is a first amplifier circuit as a multi-stage amplifier circuit consisting of amplifiers 12 and 14. 2 amplification circuit.

174, if the switching signal 18a is at L level, the voltage signal 13a is output as the radiation detection signal 17a,
When the switching signal 18a is at H level, the second cutting device 18 outputs the pressure signal 14a as the radiation detection signal 17a, and detects the value of the signal 17a, and this value is less than the predetermined value S. The signal level control circuit outputs the above-mentioned switching signal 18a as a binary signal which becomes L level when the value of signal 17a is equal to or higher than S, and becomes H level when the value of signal 17a is equal to or higher than S.

19 is assembled into a box 2, a climate control device 10 and 17, and an amplifier circuit 15.
and 16, the valve/separate circuit 18, and the power supplies @7 and 8 are collectively housed, and 20 is an ionization chamber type radiation detection device consisting of the above-mentioned parts.

In the radiation detection device 20, as long as each part is configured as described above and the one-stage width circuits 15 and 16 are healthy, the radiation detection signal 17a will be a signal corresponding to the residual dose of radiation 3 and the vehicle weight. It is clear that the dose rate I can be offset by 17a.

Also, the ionization chamber 2 and the art platform width circuit 15, 16 are in the same housing 19.
Since the length of the conductor between the ionization chamber 2 and the amplifier circuit 15.16 is shortened, the dose rate I can be accurately detected by the signal 17aVC as long as the amplifier circuit 15.16 is healthy. That is clear. Then, in the radiation detection device 20, when the St rate vehicle weight is small and the value of the signal 17a is less than the predetermined value S, the boo signal 18a becomes L level, and as a result, the ionization 1E current 2a is transmitted to the amplifier circuit 15. It is converted into a voltage and amplified, resulting in a radiation detection signal of 17m.
In this case, the electric current i2a is outputted from the switch 17 as a voltage signal 11a1'c by the first stage amplifying element 11b, which is a 1MOS type FIT, with a high input impedance.
Therefore, the detection signal 17a becomes a signal with a small detection error relative to the dose and vehicle weight, similar to the case of the radiation detection signal 5a in FIG.

However, in the radiation detection device 20, the dose vehicle weight is large (
When the value of the signal 17a becomes equal to or higher than S, the switching signal 18a becomes H level, so that the separation current 2a is converted into a voltage by the amplifier circuit 16, amplified, and finally outputted from the switching device 17 as a detection signal 17M. In this case, the ionizing current 2a is.

The input impedance is M adopted for the first stage amplification element 11b.
The voltage signal is generated by the first-stage amplifying element 12b, which employs a junction-type PET, which has a characteristic that the change in characteristics due to the large irradiation dose of radiation @3 is much smaller than that of the MOS-type PET, although it is lower than that of the OS-type FIT. 12H, so the irradiation 41! in the detection signal 17a! il coefficient horizontal error is amplifier circuit 15vc ℃ current f
Although it is slightly larger than the case where i2a is changed to signal 171, it is increased by 1 because of radiation 41!30 large irradiation dose.
1! ! It almost never happens that the characteristics of the element 12b change and the radiation mechanism of FIG. 2 becomes impossible to detect the dose rate as in the case of the device 1. Therefore, the radiation detection device fW2
0 is a t, b box type radiation emitting device that is integrated with an ionization chamber and an amplifier circuit and has a high reliability of dose rate detection.

〔Effect of the invention〕

As described above, the present invention includes a tn box that detects radiation and outputs t-discharge sweat according to the detection result, and a
A first amplifier circuit as a multi-stage amplifier circuit that employs an OS-type FET as the first-stage amplifier element (a first amplifier circuit as a multi-stage amplifier circuit that employs an OS-type FET as the first-stage amplifier element), and a second amplifier circuit as a multi-stage amplifier circuit that employs a junction-type FET as the first-stage amplifier element, and 11! Detection of radiation by switching the ionization FF flow and inputting it to the first amplifier circuit or the second width circuit, and switching each output signal of the stage width circuit according to the input switching signal. The second output as a signal
A switch and a signal level discrimination circuit that outputs the stI switching signal in response to the radiation-detection signal are integrally provided, and the output VF44! Ionization chamber type radiation 11i that detects radiation irradiation dose rate by detection signal! Igt sleep compensation, when the irradiation dose rate represented by the radiation detection signal is small, the ionization 11 fl is determined by both the switching devices and the signal level discrimination circuit.
t is input to the first amplifier circuit and output as a radiation detection signal which is the output signal of this N1 amplifier circuit, and when the irradiation dose rate represented by the radiation detection signal exceeds a predetermined value, the ionizing current is
The VC111 unboxing type radiation detection installation was configured to input the signal to the two amplifier circuits and output the output signal of the two amplifier circuits as a radiation detection signal.

Therefore, with the above configuration, when the irradiation dose rate of radiation is small and therefore the value of the ionizing current is small, a radiation detection signal corresponding to the ionizing current is output as the output signal of the first amplifier circuit. However, since a MOS type FET with high input impedance is used for the first stage amplification element of this first amplifier circuit, the ionization current is small and the radiation dose rate detection accuracy is high even at °C. II! 2
It will be output from the selector. Furthermore, with the above configuration, the irradiation dose rate of radiation may exceed the value in some places, and therefore the value of the ionizing IE current may be large and the above-mentioned MOS type FBTl'[%Q change may occur. In such a case, the radiation detection signal according to ionization [flIt] is 1
! The output signal of the @2 amplifier circuit is output from the second switch, but the first stage amplifying element of this @2 amplifier circuit has a radiation layer 114 with a large irradiation dose, although the input impedance is lower than that of the MOS type FgT. Since a junction type FET is used, which is less likely to cause changes in characteristics due to Although there is a slight decrease in accuracy, there is no situation in which it becomes impossible to detect the dose rate.

Therefore, the above configuration has the effect of providing an ionization chamber type radiation detection device with high detection reliability for radiation irradiation dose rates.

4. I! i! Brief explanation of J side Figure 1 shows one example of the present invention! A configuration diagram of a leakage example.

FIG. 2 shows the factors of a conventional ionization chamber type radiation detection device.

1, 20... Ionization chamber type radiation detection device, 2...
...Ionization chamber, 2a...Ionization WIm,
3. Curved ray, 41), 11b, 12b...-
First-stage amplification element, 6...multi-stage amplification circuit.

IO...First switch, 15...First amplifier circuit, 16...Second amplifier circuit, 17...Second
Switcher, 17a...Radiation detection signal, 18...
...Signal level discrimination circuit, 18a note recess

Claims (1)

[Claims] 1) An ionization chamber that detects radiation and outputs an ionization current according to the detection result, a first amplifier circuit as a multistage amplifier circuit that uses a MOS FET as the first stage amplifier element, and a junction type FET.
a second amplifier circuit as a multi-stage amplifier circuit employing ET as a first-stage amplifier element; and a first switching circuit that switches the ionizing current and inputs it to the first amplifier circuit or the second amplifier circuit according to an input switching signal. a second switch that switches each output signal of the two amplifier circuits according to the input switching signal and outputs it as a radiation detection signal; and a second switch that outputs the switching signal according to the value of the radiation detection signal. An ionization chamber type radiation detection device that is integrally provided with a signal level discrimination circuit and detects the irradiation dose rate of the radiation based on the radiation detection signal, wherein both the switches and the signal level discrimination circuit, When the irradiation dose rate represented by the radiation detection signal is small, the ionizing current is input to the first amplifier circuit, and the output signal of this first amplifier circuit is output as the radiation detection signal, and the radiation detection signal represents An ionization chamber type radiation detection device, characterized in that when the irradiation dose rate exceeds a predetermined value, the ionization current is input to the second amplifier circuit, and an output signal of the second amplifier circuit is output as the radiation detection signal. .