JPS62222181A - Apparatus for measuring radioactive rays - Google Patents

Abstract

PURPOSE:To obtain the titled apparatus having a wide detection range and a constant counting rate characteristic, by providing a semiconductor radiation detector in the vicinity of a radiation detector having no energy resolving power in parallel. CONSTITUTION:When radioactive rays are incident on a Geiger-Mueller pipe 1, the Mueller pipe 1 generates discharge on a reference counting rate to output a pulse to a frequency divider 3. At the same time, a detector 4 outputs a pulse having a peak value in proportion to the energy of the incident radiation rays. This pulse is amplified by an amplifier 5 to be inputted to an energy analytical circuit 6 and compared with a reference signal. At this time, signals are outputted from comparators 6a-6c and a variable frequency oscillation circuit 7 outputs a clock signal of reference frequency to a sampling gate 8 which in turn outputs the signal from the frequency divider 3 to a counter 9 with the timing corresponding to the frequency from the circuit 6. By this method, the energy of the incident radioactive rays is detected on the basis of the output from the detector 4 and the counting rate of a main detector is controlled by an electrical technique.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a technique for correcting energy resolution in a radiation measuring device using a Geiger-Mueller tube or a scintillation counter.

(Prior art) Radiation detectors such as Geiger-Mueller tubes and scintillation counters have a large area that can detect radiation, the so-called effective detection area, and are easy to handle. It is used in the detection part of Funto Ushi Monitor,
Since the variation of the counting rate with respect to the radiation energy, so-called energy dependence °i, is large (see Fig. 2)2, there is an inconvenience that the measured value must be corrected in consideration of the energy of the radiation source.

To solve such problems, use radiation! ! It has also been proposed to equalize the count rate for radiation energy by arranging a metal plate made of aluminum, lead, etc. around the detection area of the detector, but this would make the detector structure more complicated and larger. This brings about a new problem.

On the other hand, since radiation detectors using semiconductors have excellent energy resolution, it is possible to correct the count rate for radiation energy with a relatively simple circuit configuration, but on the other hand, the effective detection area is limited. However, because it is extremely small, it is unsuitable for use as a detector in radiation measuring devices such as radiation meters and foot monitors that measure large areas.

(Purpose) The present invention has been made in view of the above circumstances, and its purpose is to actively utilize the advantages of Geiger-Mueller tubes and scintillation counters and the advantages of semiconductor detectors to increase the size of the detector. The object of the present invention is to provide a new radiation measuring device which has a uniform counting rate and a large detection area without causing clutter or tank clutter.

(Structure) The details of the present invention will be described below based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a Geiger-Mueller tube that serves as a main detector for detecting radiation ji, and an anode 1a is a high voltage generator 2 that generates a high voltage. is applied, the cathode 1b is grounded via the load resistor R1, and the connection point is connected to the frequency divider 3 via the capacitor C.

4 is a semiconductor radiation detector whose output signal level changes monotonically with respect to radiation energy at least in the sensitivity region of the Geiger-Mueller tube (Fig. 2, 8), and is placed near the detection region of the Geiger-Mueller tube. In addition, its anode is grounded, and its anode is connected via an amplifier 5 to an energy analysis circuit 6, which will be described later.

6 is the energy analysis circuit described above, which inputs the signal from the input terminal or the amplifier 5 to the comparison terminal or the reference signal Vs, S, V.
Consisting of comparators 6a, 6b, and 6c receiving S3,
Each of the reference signals S1, VS2, and VS3 is set in accordance with the output level of the semiconductor radiation detector 5 in a region where the counting rate of the Geiger-Mueller tube varies depending on the radiation energy. Reference numeral 7 denotes a variable frequency oscillation circuit that changes the sampling time by changing the green repetition frequency of the clock signal to be output according to the output signal from the energy analysis circuit 6. Positive feedback is applied by a series circuit of a capacitor 7C and a resistor 7d, and two inverters 7a and 7b are connected.
Comparators 6a, 6b, 6c are connected between the connection point and the return path.
Analog switches 7e and 7f operated by signals from
, 79 to which resistors 7h, 7j, and 7k can be selectively connected. Each of these resistors 7h, A], 7 is set to a value that is inversely proportional to the oscillation frequency in the regions 1 to 2 or the frequency in the reference count rate region 3. Reference numeral 8 denotes a sunbrush gate, one input terminal of which is connected to the output terminal of the frequency divider 3, and the other input terminal connected to the output terminal of the variable frequency oscillation circuit 7. 9 is a counter that counts the pulse signals output from the subsibling gate 8, and outputs the counted content to the display 11 via the display circuit 10, and also outputs the counted content to the display 11 immediately before the sampling gate 8 is opened. is configured to clear.

Reference numeral 12 denotes an energy characteristic display circuit for displaying the approximate energy on the display 13 in correspondence with the output from the energy analysis circuit 6. In addition, the symbols R,,R in the figure
2. Day 3 shows a voltage dividing resistor for generating a reference signal.

In this embodiment, when the device is brought close to the radiation source, a Geiger-Mueller tube 1 and a semiconductor radiation detector 4 are used to detect radiation in the energy range (N in FIG. 2) that produces pulses at a reference count rate.
, the Geiger-Mueller tube 1 generates a discharge at a reference counting rate and outputs a pulse to the frequency divider 3. At the same time, the semiconductor radiation detector 4 outputs a pulse having an extremely high peak value in proportion to the energy of the incident radiation.

After this pulse is amplified by an amplifier 5, it is input to an energy analysis circuit 6 for each reference signal Vs, VS2 . Compare with VS3. In this case, since the peak value of the incident pulse is extremely high, a signal is output from each of the comparators 6a to 6C. Thereby, the variable frequency oscillation circuit 7 outputs a clock signal of the reference frequency to the sampling gate 8. The sampling gate 8 outputs the signal from the frequency divider 3 to the counter 9 with a time T1 corresponding to the frequency from the variable frequency oscillation circuit 6 (Fig. 3). As a result, the number of pulses per sampling cycle inputted to the counter 9 is not corrected, and the measurement result that is determined by the radiation dose is displayed on the display 11.

On the other hand, the energy region (second
When the radiation of the radiation source (Fig. Output to frequency generator 3.

At the same time, the semiconductor radiation detector 4 outputs a pulse having an extremely low peak value in proportion to the energy of the incident radiation. After this pulse is amplified by an amplifier 5, it is inputted to an energy analysis circuit 6 to provide each reference signal VSt, VS2.
, compared with VS3. In this case, since the peak value of the incident pulse is extremely low, no signal is output from any of the comparators 6a to 6C, and the variable frequency oscillation circuit 7 receives a high frequency clock signal commensurate with the increase in the counting rate. is output to the sampling gate 8.

The sustaining gate 8 outputs the signal from the frequency divider 3 to the counter 9 at a time T2 corresponding to the frequency of the variable frequency oscillation circuit 6 (FIG. 3 II). As a result, the number of pulses per sampling cycle input to the counter 9 is suppressed, and regardless of the increase in the counting rate of the Geiger-Mueller tube, the measurement result that is completely defeated by the radiation dose is displayed on the display 1.
1 will be displayed.

Hereinafter, the peak value of the signal output from the semiconductor radiation detector 4 is detected one by one in this way, and the frequency of the variable frequency oscillation circuit 7 is changed to control the sampling cycle, and the counter 9 is calculated for the unit number of doses. Adjust the counted value to a constant value.

In addition, the energy characteristic display circuit] 2 displays the approximate energy of the incident radiation on the display] 3 in response to the signal from the energy analysis circuit 6 to provide the operator with information about the type of radiation source. I will provide a.

FIG. 4 shows a second embodiment of the present invention,
Reference numeral 20 in the figure represents a frequency divider with a variable division ratio, and the output pulse from the Geiger-Mueller tube 1 is input to the input terminal of the frequency divider.
Further, a signal from the energy analysis circuit 6 described above is input to the control terminal, and the branching ratio is changed in accordance with the energy of the radiation. 2] is a clock oscillator with a constant repetition frequency, and one input terminal receives a signal from the variable division ratio frequency divider 20, and the other input terminal of the sampling gate 8 receives a sampling pulse with a constant time width. This outputs the following.

In this embodiment, when the Geiger-Mueller tube 1 receives radiation having the energy (■ in Figure 2) to output a pulse at the standard count rate, the semiconductor radiation detector 4 outputs a pulse with a low peak value. is output. The energy analysis circuit 6 maintains the frequency division ratio of the variable frequency divider 2o at a reference value based on the peak value of this pulse, and maintains the number of pulses from the Geiger-Mueller tube 1 input to the sampling gate 8 at the reference value. .

On the other hand, when radiation (see Fig. 2) having the energy to increase the counting rate of the Geiger-Mueller tube enters the Geiger-Mueller tube 1, the semiconductor radiation detector 4 outputs a pulse with a high peak value. The energy analysis circuit 6 is
Based on the peak value of this pulse, the frequency division ratio of the frequency divider 20 is increased, and the repetition frequency of the pulse from the Geiger-Mueller tube 1 input to the sampling gate 8 is decreased.

As a result, the number of pulses input to the counter 9 within a certain time is reduced for radiation in an energy band where the counting rate is high, and the number of pulses is increased for an energy band where the counting rate is low, thereby increasing the energy of the radiation. To perform display at a constant counting rate regardless of the

FIG. 5 shows a third embodiment of the present invention,
Reference numeral 22 in the figure is a voltage variable type high voltage generation circuit, whose output terminal is connected to the anode 1a of the Geiger-Mueller tube, and whose voltage control terminal is connected to the output terminal of the energy analysis circuit 6. is divided at a constant ratio by a frequency divider 3, and then inputted to a counter 9 through a sampling gate 8 which is opened and closed at a constant frequency from a clock oscillator 21.

According to this embodiment, the output voltage of the variable voltage high voltage generation circuit 22 is adjusted by the signal from the energy analysis circuit 6, and the counting rate of the Geiger-Mueller tube 1 itself is adjusted in accordance with the incident radiation. Energy dependence can be corrected.

In this example, the sensitivity region of the Geiger-Mueller tube is divided into four, or the number of divisions of the sensitivity region is a design matter determined by the energy dependence of the main detector and the required accuracy. Yes, but it is not limited to this.

In this embodiment, the semiconductor radiation detector can be provided independently of the Geiger-Mueller tube, or it can be housed inside the Geiger-Mueller tube, thereby reducing the size of the detection section.

Briefly, in the above-mentioned embodiment, the case where the energy dependence of the count rate in a Geiger-Mueller tube is corrected was taken as an example, but other radiation detectors that depend on the count rate or radiation energy, such as scintillation counters It is clear that the same effect can be achieved even when applied to a radiation measuring device using

(Effects) As explained above, according to the present invention, a semiconductor radiation detector is installed in parallel near a radiation detector with no energy resolving property, and the energy of incident radiation is absorbed by the output from the semiconductor radiation display device. Based on this, the count rate of the main detector is controlled electrically, resulting in a radiation measurement device that maintains a simple structure and has a wide detection area and constant count rate characteristics. can be realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a device showing an embodiment of the present invention, and Fig. 2 shows the energy dependence of the count rate in the Geiger-Mueller tube used in the same device and the change in output level with respect to energy of the semiconductor radiation detector. A characteristic diagram, FIG. 3 is an explanatory diagram showing the operation of the same device, and FIG. 4.5 is a block diagram showing another embodiment of the present invention. ] ...Geiger-Mueller tube 4 ...Semiconductor radiation detector 6 ...Energy analysis circuit 8 ...Sampling gate Applicant Orient Watch Co., Ltd. Agent Patent attorney Haruto Nishikawa Katsuhiko Kimura Figure 2 Figure 3

Claims (1)

[Claims] A main detector consisting of a Geiger-Mueller tube or a scintillation counter, a semiconductor radiation detector disposed near the detection area of the detector, and means for determining radiation energy based on the output level from the semiconductor detector. , a radiation measuring device comprising means for controlling the counting rate of the main detector based on the determination result of the means.