WO2013114599A1

WO2013114599A1 - Radiation measuring device

Info

Publication number: WO2013114599A1
Application number: PCT/JP2012/052334
Authority: WO
Inventors: 渡辺　公貴; 加藤　國彦; 貴信海上
Original assignee: 株式会社タカラトミー
Priority date: 2012-02-02
Filing date: 2012-02-02
Publication date: 2013-08-08
Also published as: JP5760100B2; JPWO2013114599A1

Abstract

Provided is a radiation measuring device which can be manufactured easily at low cost and has high sensitivity and high noise removal accuracy. A radiation measuring device is provided with a plurality of semiconductor sensors which each detect incidence of radiation and output a predetermined detection signal, and a signal reading means which acquires the detection signal outputted from each of the semiconductor sensors. When the detection signal has been inputted from any one of the plurality of semiconductor sensors, the signal reading means performs determination processing for, at the timing when the detection signal has been inputted, determining whether or not the detection signals have been inputted from the other semiconductor sensors, and when determining that the detection signals have been inputted from all of the plurality of semiconductor sensors, the signal reading means determines that the detection signal is noise, and when determining that the detection signal has not been detected from at least one of the plurality of signal reading means, the signal reading means determines that the detection signal results from correct detection of radiation.

Description

Radiation measurement equipment

This invention relates to a radiation measuring apparatus.

Conventionally, there has been a radiation measuring apparatus that measures radiation dose by directly detecting radiation such as gamma rays or X-rays using a semiconductor detection element such as a photodiode or phototransistor, or indirectly by converting the radiation into visible light using a scintillator or the like. is there. In the semiconductor detection element used in this radiation measuring apparatus, photoexcitation occurs in the depletion layer on the PN junction surface due to incident electromagnetic waves, and an amount of electrons and holes approximately proportional to the amount of light are generated in pairs. In the radiation measuring apparatus, electrons and holes generated by the semiconductor detection element flow as a pulse current to the charge amplifier and are converted into voltage changes, and the incidence of radiation is detected by detecting this voltage change.

Since the voltage change measured by such a radiation measuring apparatus is at a very small level, various improvements have been conventionally made in the radiation measuring apparatus to improve the detection capability. One technique for improving the detection capability is to increase the sensitivity of the semiconductor detection element. In the semiconductor detection element, by increasing the volume of the depletion layer, more charge pairs are generated with respect to radiation having the same amount of incident light, so that sensitivity is increased. In order to increase the volume of the depletion layer, it is conceivable to increase the area of the PN junction surface. However, when the PN junction surface is simply widened, the detection voltage with respect to the same incident light quantity is decreased in inverse proportion to the junction area, so that there is a problem that the influence of noise becomes relatively large. Therefore, conventionally, a technique has been developed in which a plurality of semiconductor detection elements are arranged in parallel to detect radiation independently, and the detection results are added together (for example, Patent Documents 1 and 2).

In addition, when weak radiation is detected using a plurality of photodiodes, detection in each photodiode is independent and intermittent. Therefore, the possibility that radiation is detected simultaneously by a plurality of photodiodes is very low. Therefore, Patent Document 3 includes a non-coincidence counting circuit, and when radiation detection waveforms are simultaneously input from a plurality of semiconductor detectors, noise due to other factors (for example, vibration of the radiation detection apparatus). It is disclosed about the technique considered to be excluded from the count.

JP 2009-139346 A Japanese Patent No. 4643809 Japanese Patent No. 3750924

However, the noise determination technique disclosed in Patent Document 3 is different from a signal detection operation of a predetermined threshold value or more performed based on an analog signal waveform output from each radiation detection unit arranged in parallel. The determination operation of the asymmetry of the detection timing by the semiconductor detector is collectively performed as needed. Therefore, there is a problem that the configuration and operation are complicated, leading to an increase in size and an increase in power consumption.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a radiation measurement apparatus that can be easily manufactured at low cost and has high sensitivity and high noise removal accuracy.

In order to achieve the above object, the invention described in claim 1
A plurality of semiconductor sensors that detect the incidence of radiation and output a predetermined detection signal;
Signal reading means for acquiring the detection signal output from each of the semiconductor sensors;
With
The signal reading means is
When the detection signal is input from any one of the plurality of semiconductor sensors, whether or not the detection signal is input from another semiconductor sensor at the timing when the detection signal is input. When a determination process is performed to determine that the detection signal is input from all of the plurality of semiconductor sensors, the detection signal is determined to be noise, and from at least one of the plurality of signal means, the When it is determined that a detection signal is not detected, the radiation measurement apparatus is characterized in that it is determined that the detection signal is a result of correctly detecting radiation.

The invention according to claim 2 is the radiation measuring apparatus according to claim 1,
The signal reading unit performs the determination process as an interrupt process triggered by the input of the detection signal.

The invention according to claim 3 is the radiation measuring apparatus according to claim 1 or 2,
The plurality of semiconductor sensors are:
When radiation is incident, a radiation detection unit that generates and outputs a signal corresponding to the radiation, and
And a noise identifying unit that outputs a pulse signal having a predetermined width as the detection signal when the wave height of the signal output from the radiation detection unit exceeds a predetermined threshold.

The invention according to claim 4 is the radiation measuring apparatus according to claim 3,
The signal reading means counts the number of input pulse signals output from the plurality of noise identifying units at the timing when the detection signal is input in the determination processing, and the number of inputs is the plurality of semiconductor sensors. It is characterized in that the determination is performed depending on whether or not the number is equal.

The invention described in claim 5
A plurality of semiconductor sensors that detect the incidence of radiation and output a predetermined detection signal;
Signal reading means for acquiring the detection signal output from each of the semiconductor sensors;
With
The signal reading means counts the number of the input detection signals every predetermined time interval,
When the counted value is equal to or larger than a preset reference value, it is determined that noise is mixed in the counted value.

A sixth aspect of the present invention is the radiation measuring apparatus according to the fifth aspect,
A display unit for displaying information;
The signal reading unit causes the display unit to display an error when it is determined that the noise is mixed in the counted value continuously for a predetermined reference number or more. It is a feature.

According to the present invention, there is an effect that a radiation measuring apparatus with high radiation detection sensitivity and high noise removal accuracy can be manufactured easily and at low cost.

It is a block diagram which shows the outline of the whole structure of the radiation measuring device of embodiment of this invention. It is a figure which shows the outline of the circuit structure of a radiation detection part. It is a flowchart which shows the control procedure of the initial setting process in radiation measurement operation | movement. It is a flowchart which shows the control procedure of the discrimination | determination count process in a radiation measurement operation | movement. It is a flowchart which shows the control procedure of the arithmetic processing in a radiation measurement operation | movement.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an overall configuration of a radiation measuring apparatus according to an embodiment of the present invention.

The radiation measuring apparatus 1 of the present embodiment includes four semiconductor sensors 11 to 14 and a control unit 31 (signal reading means) provided in parallel. The semiconductor sensor 11 includes a radiation detection unit 21 and a detection discrimination unit 26 (noise identification unit), and the semiconductor sensor 12 includes a radiation detection unit 22 and a detection discrimination unit 27. The semiconductor sensor 13 includes a radiation detection unit 23 and a detection discrimination unit 28, and the semiconductor sensor 14 includes a radiation detection unit 24 and a detection discrimination unit 29.

FIG. 2 is a circuit block diagram showing an outline of a circuit configuration related to the radiation detection unit 21.

The radiation detection unit 21 of this embodiment includes a photodiode D1, a charge amplifier unit OA11, and an amplification unit OA21 connected in series. Since the radiation detection units 22 to 24 have the same configuration as the radiation detection unit 21, description thereof is omitted.

The cathode end of the photodiode D1 is connected to the output terminal of the bias voltage Vbias via the resistor R11. On the other hand, the anode end of the photodiode D1 is connected to the inverting input terminal of the operational amplifier OP21 included in the charge amplifier unit OA11. A predetermined reference voltage is input to the non-inverting input terminal of the operational amplifier OP21. A resistor R21 and a capacitor C21 are connected in parallel to the operational amplifier OP21. The operational amplifier OP21, the resistor R21, and the capacitor C21 constitute a charge amplifier unit OA11 that converts the charge generated by the photodiode D1 into an output voltage.

If the capacitance of the capacitor C21 used in the charge amplifier section OA11 is small, the voltage to be converted increases and noise increases. If the capacitance is large, the voltage decreases and noise also decreases. Is set to an appropriate value. Further, the resistor R21 determines the discharge speed of the electric charges that are output in a pulse form from the photodiode D1 and are temporarily stored in the capacitor C21. The resistance value of the resistor R21 is desirably a high value from the relationship with the detection duration, but if it is too high, the resistance value is easily affected by electric field noise, and therefore is set appropriately within a range not exceeding the impedance of the photodiode D1. The operational amplifier OP21 is a low-noise amplifier with particularly low noise, and a slew rate and a gain band corresponding to the width (for example, about 50 μs) of the detection voltage waveform at the time of gamma ray detection is selected.

The amplification unit OA21 is connected to the charge amplifier unit OA11 via a capacitor C31 connected to the output terminal of the operational amplifier OP21 and a resistor R31 connected to the other end of the capacitor C31. Functions as a band filter (mainly a low-pass filter). The amplifier OA21 includes an operational amplifier OP41, a capacitor C41, and a resistor R41 that are connected in parallel to the other end of the resistor R31. The output voltage of the amplifying unit OA21 is output to the detection discriminating unit 26 as an analog voltage waveform Vout via the capacitor C51 and the resistor R51.

The detection discriminating units 26 to 29 each generate a pulse signal (detection signal) indicating detection when a voltage equal to or higher than a preset threshold voltage is detected in the voltage waveforms input from the radiation detection units 21 to 24, respectively. A discriminator that outputs to the control unit 31 is included. Here, the signals output from the detection discriminators 26 to 29 are, for example, “0” signal (low level signal) in the normal state, and “1” signal (high level signal) when the detection signal is output. Such a binary signal is used. As described above, the detection discriminators 26 to 29 can output a binary signal whose output changes at the timing when a voltage equal to or higher than the threshold voltage is detected, and may have a simple configuration. For example, the discriminator It is good also as including a comparator instead of. In addition, the process of converting the voltage waveform data and the detection signal into discrete data (digital data) at a predetermined sampling frequency at this stage increases power consumption due to unnecessary processing, and causes an error in detection timing. Not needed.

The control unit 31 controls the operation of each unit of the radiation measuring apparatus 1 and determines whether or not the detection signals input from the detection discriminating units 26 to 29 are caused by noise, as will be described later. The number of detection signals that are determined not to be noise, that is, the detection signal indicating that the radiation has been correctly detected is counted. In addition, the control unit 31 converts the count value within the time period into a value (output value) based on a measurement unit for output (for example, dose equivalent (Sv / h)) at predetermined time intervals (for example, 1 minute). Performs conversion processing.

The control unit 31 is, for example, a microcomputer, and includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The ROM stores a program for causing the determination processing and calculation processing performed by the control unit 31 to be executed in software. When measuring radiation, this program is read out by the CPU, loaded into the RAM, and executed. Parameters necessary for conversion to an output value, that is, a value such as the detection efficiency of an observation device, or a conversion formula including the detection efficiency is stored in advance in the RAM.

The control unit 31 displays an output value calculated by sending a drive control signal to a display unit (not shown) (for example, an LCD (liquid crystal display)), or transmits the output value to an external device via a communication interface. The output values can be sequentially stored in the RAM as history data.

Next, the operation of the radiation measuring apparatus 1 of the present embodiment will be described.
In the radiation measurement apparatus 1 of the present embodiment, as shown in FIGS. 1 and 2, semiconductor sensors 11 to 14 are provided in parallel. The detection signals output from the detection discriminating units 26 to 29 are input to the control unit 31 independently.

3A to 3C are flowcharts showing the control procedure of each process executed by the CPU of the control unit 31 during the radiation measurement operation.

The process related to the measurement of radiation is automatically started, for example, when the power of the radiation measurement apparatus 1 is turned on. At this time, the CPU of the control unit 31 executes an initial setting process as shown in FIG. 3A. When the initial setting process is started, the CPU sets the counter value to “0” and stores it in the RAM (step S101). In addition, the CPU sets a conversion to an output value and an output interval of the output value, and operates a timer that generates an interrupt signal for arithmetic processing at each interval (step S102). Then, the initial setting process ends.

Next, when any of the signals input from the detection discriminating units 26 to 29 to the control unit 31 changes to a signal indicating detection, the CPU of the control unit 31 starts an interrupt process using the detection of the change as a trigger. To do. In this interrupt process, the CPU executes the discrimination counting process shown in FIG. 3B. First, the CPU determines whether or not a detection signal is also input from three detection discrimination units other than the detection discrimination unit that outputs the detection signal (step S111). Specifically, in the radiation measuring apparatus 1 of the present embodiment, the CPU adds up the values of the input signals from the detection discriminating units 26 to 29, and the total value is the number of the detection discriminating units 26 to 29 (ie, 4). Whether or not is equal. When it is determined that the total value is equal to the number of detection discriminating units, the detection signals are input from all the detection discriminating units 26 to 29. Therefore, the CPU regards the detection signals as noise. Judgment is abandoned, and interrupt processing is terminated as it is. On the other hand, if it is determined that the detection signal is not input from at least one of the detection discriminating units, the CPU determines that this detection signal is the one that has detected the radiation correctly, and stores it in the RAM. 1 is added to the counter value (step S112). Alternatively, in the process of step S112, the above total value may be added to the counter value. Then, the interrupt process ends.

Further, when the interrupt signal related to the arithmetic processing is input by the timer operation, the CPU of the control unit 31 acquires the counter value stored in the RAM as shown in FIG. 3C (step S121). Then, the CPU converts this counter value into an output value (step S122). The CPU performs an output process of displaying the calculated output value on the display unit or transmitting the output value to the outside (step S123). Thereafter, the CPU resets the counter value stored in the RAM and the timer operation (step S124). Then, the CPU ends the interrupt process.

In the radiation measuring apparatus 1, the value output interval can be set shorter than the counter value acquisition interval. For example, when the output interval is 10 seconds with respect to the acquisition interval of 60 seconds, the counter value for every 10 seconds is stored in the latest 6 RAMs, and the output value is calculated based on the 6 total counter values. Conversion can be performed. At this time, the oldest count value data that is no longer necessary is overwritten and updated with the next count value, thereby enabling continuous operation without storing unnecessary data in the RAM.

As described above, the radiation measuring apparatus 1 according to the present embodiment includes the plurality of semiconductor sensors 11 to 14 and the control unit 31, and the control unit 31 includes the detection discriminating units 26 to 29 of the semiconductor sensors 11 to 14. The predetermined detection signals respectively output from are acquired. When a detection signal is input from one of the detection discriminating units 26 to 29, the control unit 31 determines whether or not a detection signal is input from another detection discriminating unit, and from all of the detection discriminating units 26 to 29. If it is determined that the detection signal is input at the same time, the detection signal is determined to be noise and abandoned. If the detection signal is not input simultaneously from at least one of the detection discriminators 26 to 29, the detection signal is valid. It is determined as a detection signal and added to the number of detections. By providing such a configuration, the radiation measuring apparatus 1 can increase the detection sensitivity of the radiation detection unit without reducing the detection voltage. On the other hand, the control unit 31 can easily detect noise by determining the simultaneity of the input signals from the plurality of detection discriminating units 26 to 29 based on the binary data input from any of the detection discriminating units 26 to 29. Make a decision. Therefore, the control unit 31 can easily perform further noise removal and improve the detection accuracy.

Further, in this radiation measurement apparatus 1, since the detection signal is acquired as an interrupt signal, it is not always necessary to sample input data, and a large load is not constantly applied to the CPU of the control unit 31.

Further, in the radiation measuring apparatus 1 of the present embodiment, the semiconductor sensors 11 to 14 simply detect a voltage waveform that exceeds the threshold by using a discriminator, a comparator, or the like to generate a detection signal, and send it to each control unit 31. Since only the output is required, the labor at the time of manufacture is simplified. In addition, it is not necessary to perform clock synchronization of the operations of the radiation detectors 21 to 24 and the detection discriminators 26 to 29 or to perform data sampling at a high frequency, and noise determination and radiation detection can be easily performed. . That is, the radiation measuring apparatus 1 can be controlled by an inexpensive microcomputer. Therefore, the manufacturing cost of the radiation measuring apparatus 1 can be reduced.

Further, in this radiation measuring apparatus 1, the number of semiconductor sensors 11 to 14 arranged in parallel can be easily increased or decreased, so that it can be easily changed based on the required sensitivity, the size of the radiation measuring apparatus 1, and the like. I can do it. Further, since it is easy to determine an input error, it is possible to easily display an error.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above embodiment, whether or not the detection signals from the detection discriminating units 26 to 29 are all inputted in the same way is determined by software in the control unit 31. It is good also as providing the structure which performs a discrimination | determination process easily by providing.

Further, the specific configuration of the radiation detectors 21 to 24 is not limited to that shown in the above embodiment. For example, a phototransistor may be used instead of the photodiode, or another form may be used as the charge amplifier. The outputs of the detection discriminating units 26 to 29 may be active low. The number of radiation detection units is not limited to four, and is set to an appropriate value of 2 or more according to sensitivity and circuit scale.

In the above embodiment, only the simultaneity of the detection signals from all the detection discriminators 26 to 29 is shown as a criterion for determining the noise. Even when a large number of counter values are obtained, it may be determined that there is noise. In addition, other known noise filtering techniques that do not increase the size and do not complicate the circuit configuration, in particular, those that can be implemented in software may be used in combination. In addition, when noise determination is continuous, an error signal may be output or an error may be displayed on the display unit.
In addition, the specific numerical values and details shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

Industrially available fields

The present invention can be used for an apparatus for detecting and measuring radiation.

DESCRIPTION OF SYMBOLS 1 Radiation measuring device 11-14 Semiconductor sensor 21-24 Radiation detection part 26-29 Detection discrimination part 31 Control part C21, C31, C41, C51 Capacitor D1 Photodiode OA11, OA21 Charge amplifier part OP21, OP41 Operational amplifier R11, R21, R31 , R41, R51 resistance

Claims

A plurality of semiconductor sensors that detect the incidence of radiation and output a predetermined detection signal;
Signal reading means for acquiring the detection signal output from each of the semiconductor sensors;
With
The signal reading means is
When the detection signal is input from any one of the plurality of semiconductor sensors, whether or not the detection signal is input from another semiconductor sensor at the timing when the detection signal is input. When a determination process is performed to determine that the detection signal is input from all of the plurality of semiconductor sensors, the detection signal is determined to be noise, and the detection signal is determined from at least one of the plurality of signal means. A radiation measuring apparatus, characterized in that, when it is determined that a detection signal is not detected, it is determined that the detection signal is a result of correctly detecting radiation.
2. The radiation measuring apparatus according to claim 1, wherein the signal reading means performs the discrimination process as an interrupt process triggered by an input of the detection signal.
The plurality of semiconductor sensors are:
When radiation is incident, a radiation detection unit that generates and outputs a signal corresponding to the radiation, and
3. A noise identification unit that outputs a pulse signal having a predetermined width as the detection signal when the wave height of the signal output from the radiation detection unit exceeds a predetermined threshold value, respectively. The radiation measuring apparatus described in 1.
The signal reading means counts the number of input pulse signals output from the plurality of noise identifying units at the timing when the detection signal is input in the determination process, and the number of inputs corresponds to the plurality of semiconductor sensors. The radiation measurement apparatus according to claim 3, wherein the determination is performed based on whether or not the number is equal to the number.
A plurality of semiconductor sensors that detect the incidence of radiation and output a predetermined detection signal;
Signal reading means for acquiring the detection signal output from each of the semiconductor sensors;
With
The signal reading means counts the number of the input detection signals every predetermined time interval,
When the counted value is equal to or greater than a preset reference value, it is determined that noise is mixed in the counted value.
A display unit for displaying information;
The signal reading unit causes the display unit to display an error when it is determined that the noise is mixed in the counted value continuously for a predetermined reference number or more. The radiation measuring apparatus according to claim 5, characterized in that: