JPS6042672A - Measuring device of radiation dose - Google Patents

Abstract

PURPOSE:To improve an energy characteristic while maintaining high-speed operation by providing a discriminator which discriminates the wave height of the output of a sensor and a correcting means which gives the output of the discriminator a constant corresponding to the energy characteristic. CONSTITUTION:An incident radiation signal to a semiconductor sensor 1 is amplified by a preamplifier 2 and the discriminators 3-1-3-n discriminate the wave height. A correcting circuit 4 gives correcting coefficients matching with energy characteristics (a)-(d) of the numbers of output pulses of the respective discriminators to obtain characteristics shown by broken lines b', c', and d', and those characteristics are summed up to obtain a uniform response A over the entire energy range; and dose conversion is performed and the result is displayed on a display part 5. Thus, the size and weight of the measuring device are reduced by using energy correction system with pulse wave height detection.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a radiation dosimetry device.

Conventional configuration and its problems From low dose rate of 0.1mR/hr or less to 100OR/h
A radiation detector using a compound semiconductor as a detection material has been developed as a device capable of measuring high dose rates up to r or more (Japanese Patent Application No. 57-210761). However, since this is mainly a radiation detection method that outputs one electric pulse for each incident radiation, the dependence of photon energy versus dose sensitivity (hereinafter referred to as energy characteristics) is large, and semiconductors -2- Depending on the material, the difference from the standard can be as much as 200 times, and unless this property is improved, it cannot be used as a dosimeter. Regarding the method of improving energy characteristics, a method of improving energy characteristics using pulse height information from a detector is applied to relatively large equipment such as area monitors that require high accuracy. JP-A-57-100364 and 100365@ as applied to portable dosimeters
Those described in , etc. have been developed in recent years. For radiation safety reasons, portable dosimeters must measure with high precision over a wide range of dose rates, from low dose rates of 0.1 mR/hr to solid line rates of 10 OR/hr or more, and high-speed pulse measurement is the most important factor. This becomes a problem. In this respect, the energy correction described in the above-mentioned publication cannot maintain high speed because the pulse height is converted into time. In other words, this causes deterioration of the high linearity ratio characteristics and is not suitable as an energy correction method for high linearity ratios.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a radiation dose measuring device that can easily improve energy characteristics while maintaining high speed.

Structure of the Invention In order to achieve the above object, the radiation dose measuring device of the present invention includes at least one discriminator for classifying the pulse height of output pulses from a semiconductor sensor, and a method for determining the number of output pulses of each discriminator. This configuration includes a correction means for providing a constant corresponding to energy characteristics.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a circuit block diagram of a radiation dose measuring device according to an embodiment of the present invention, in which 1 is a semiconductor sensor, 2 is a preamplifier, 3-1 to 3-n are discriminators, 4 is a correction circuit, and 5 is a display. , R1-Rn are resistances.

The incident radiation signal generated in the semiconductor sensor 1 to which the voltages supplied from H and V are applied is amplified by the preamplifier 2, and the wave height is be discriminated against. A correction coefficient corresponding to each energy is given by the correction circuit 4 to the number of output pulses from each of the discriminators 3-1 to 3-n, the dose is converted, and the result is displayed on the display unit 5.

The operation of the correction circuit 4 will be explained with reference to FIG. The comparison level of the discriminators 3-1 to 3-n is divided into n stages (in this explanation, there are 4 stages) according to the photon energy.
Set to . The energy characteristics of the number of output pulses from each discriminator 3-1 to 3-4 are shown by the solid lines a, b in the figure.
This corresponds to c and d.

Here, the solid line a is the one where the comparison voltage is low, and the solid line a is
c, and the solid line d is the largest one. Solid line a,
For each of b, c, and d, the energy characteristics change within a range of 100 times to several times the reference value, and the measurable energy range also changes. The correction circuit 4 applies appropriate correction coefficients to each of these solid lines a to d, for example α1. α2.
By assigning each coefficient of α3 to each discriminator output, characteristics such as those shown by the broken lines b', ', and d' in the figure can be obtained. , d', a uniform response is shown over the entire energy range as shown by the solid line A.

FIG. 3 shows a more specific embodiment, in which 3 is a discriminator, 6 is a reference oscillator, 7 is an AND circuit, 8 is an exclusive OR circuit, 9 is a counting circuit, 10 is a microcomputer, VR, VRl is a variable resistance.

A signal of incident radiation from the semiconductor sensor 1 is amplified by a preamplifier 2 and subjected to wave height separation by a discriminator 3.degree. 3-1. The discriminator 3 aims to separate output pulses from noise and extracts pulses from a low energy region. The discriminator 3-1 extracts pulses in the high energy region. Discriminator 3-
The gate consisting of the AND circuit 7 is opened only during the pulse width that passes through 1, and the pulse signal of the reference oscillator 6 is allowed to pass.

The output pulse of the discriminator 3 and the output pulse of the AND circuit 7 are added by the exclusive OR circuit 8, and the dose value is converted by the counting circuit 9 and the micro combi coater 10. Display the dose value.

Figure 4 is a time chart of the operation of the circuit shown in Figure 3.
A is an output pulse from the preamplifier 2, and a high-energy output pulse shows that the pulse height increases. b indicates the output from the discriminator 3, in which all the numbers of detected radiations are output. C indicates the output of the discriminator 3-1. Here, only the output for the high energy component is extracted. As can be seen from b and c, the output pulse width of the high-energy radiation is larger than that of the low-energy radiation, and the pulse width of b is larger than the pulse width of C. d is a pulse output from the reference oscillator 6. e is the output from the AND circuit 7. The value of the energy correction coefficient is changed by changing the frequency of this reference oscillator 6. Due to the time difference between the reference pulse and the output pulse, the correction value per output pulse changes by 1 to 2 pulses, but the average value of -7 due to multiple pulses varies.
= Due to equalization, the value becomes stable as a whole. f is an output pulse from the exclusive OR circuit 8, and is an energy-corrected output.

FIG. 5 shows another specific example, 11-1 to 11-
n is a branching unit. Note that these branch units 11-1 to 11-
n has a subtraction ratio corresponding to the energy characteristics of the output of each discriminator 3-1 to 3-n.

The pulse output from the preamplifier 2 is subjected to pulse height discrimination by a plurality of discriminators 3-1 to 3-n, and each output is given a coefficient corresponding to each energy by a frequency divider 11-1 to 11-0. The microcomputer 13 adds the output pulses of each of the branching units 11-1 to 11-n, converts the dose value, and displays the dose value on the display unit 5.

FIG. 6 shows yet another specific embodiment. In this embodiment, output pulses from a plurality of discriminators 3-1 to 3-n are input to the microcomputer 10, and
A constant corresponding to the energy characteristic is assigned in the microcomputer 10, added, and converted into -8-dose10, after which the dose value is displayed on the display unit 5.

In the embodiments shown in FIGS. 5 and 6, which circuit to adopt may be determined depending on the calculation speed of the microcomputer 10 used. In other words, the embodiment shown in FIG. 5 is disadvantageous in that it requires additional frequency dividers 11-1 to 11-n; 11-1 to 11-n, the speed of the microcomputer 10 is significantly reduced.
It is advantageous in that it can be used.

As described in detail, the present invention employs an energy correction method based on pulse height detection, which was conventionally applicable only to large equipment such as area monitors.
It can be made small and lightweight to the point of being portable, and it can achieve a wide range of Iil dose rate characteristics from low dose rates to thick dose rates and widely uniform energy characteristics. This results in
It is possible to measure with high precision everything from natural radiation dose levels to IiI dose rates at the time of an accident, making a significant contribution to radiation safety management. Furthermore, since the number of parts can be reduced and the current consumption can be reduced, by applying it as a portable device, it is possible to provide a pocket-type radiation dose measuring device that is unprecedentedly compact and highly accurate.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of a radiation weight measuring device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the same device, and Fig. 3 is a diagram illustrating the operation of the device.
The figure is a circuit block diagram of a radiation dose measuring device in a more specific embodiment, FIG. 4 is a signal waveform diagram of each part of the circuit block shown in FIG. 3, and FIGS. It is a circuit block diagram of a radiation dose measuring device in an example. 1...Semiconductor sensor, 2...Preamplifier, 3-1
~3-n... Discriminator, 4... Correction circuit, 5... Display section, 6... Reference oscillator, 7... AND circuit, 8... Exclusive OR circuit, 9... Counting circuit, 10... Microcomputer, 11-1 to 11-
n... Frequency divider agent Yoshihiro Morimoto-10 = -, :i Mihajisakaiohikaki400 Figure 4

Claims (1)

[Claims] 1. At least one discriminator for classifying the pulse height of output pulses from a semiconductor sensor, and a correction means for imparting a constant corresponding to energy characteristics to the number of output pulses of each discriminator. Radiation IIa with
Quantity measuring device. 2. The radiation dose measuring device according to claim 1, wherein the correction means includes a circuit that performs an AND operation between the output pulse width of the discriminator and a reference oscillation signal having a narrower width than the output pulse width of the discriminator. 3. The radiation dose measuring device according to claim 1, wherein the correction means includes a frequency divider having a brightness attenuation ratio corresponding to the energy characteristic at each stage subsequent to each discriminator. 4. The radiation dose measuring device according to claim 3, wherein the correction means includes a microcomputer that adds and stores the output pulses of each frequency divider. 5. The correction means converts the output from each discriminator into
2. The radiation dose measuring device according to claim 1, wherein the radiation dose measuring device is configured to input data to a microcomputer having a calculation function for providing constants corresponding to energy characteristics.