JP2014126556A - Radiation dosimetry device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation dosimetry device capable of measuring radiation dose more accurately even when noise is generated.SOLUTION: A pulse identification unit 20, which compares a feature of a radiation detection pulse generated when a radiation detection unit 10 detects radiation and a feature of an output signal provided by the radiation detection unit 10, determines if generation of the output signal results from the detection of the radiation. An operation unit 30, when it is determined that the generation of the output signal results from the detection of the radiation, measures radiation dose by using the output signal. In addition to the feature of the radiation detection pulse, a feature of a noise pulse output when noise is detected is also available for pulse identification.

Description

  The present invention relates to a radiation dose measuring apparatus.

  Conventionally, radiation dose measuring apparatuses have been mainly used by workers engaged in radiation work in radiation control areas in nuclear power plants, radiation-related laboratories, hospitals, and the like. For example, by detecting radiation leakage due to an accident or failure of a radiation generator in a radiation management area, an operator can evacuate to a safe place. In addition, the radiation dose measuring device may measure the absorbed dose (μSv) of radiation that is exposed to the worker during daily work. However, since the occurrence of the Fukushima Daiichi nuclear power plant accident due to the Great East Japan Earthquake, radiation dose measuring devices have been used in ordinary households. For example, a radiation dose measuring apparatus is used for grasping an area with a high radiation dose called a hot spot or for personally managing an exposure dose.

  By using a semiconductor sensor for radiation detection, the radiation dose measuring device can be reduced in size and power consumption. However, when a physical shock or vibration is applied to the radiation dose measuring device, the semiconductor sensor generates a noise pulse that is a noise signal. This causes a reduction in measurement accuracy. In order to accurately measure the radiation dose, it is necessary to distinguish between a radiation detection pulse generated by the incidence of radiation and a noisy pulse generated by impact or vibration, and use the radiation detection pulse as a measurement target.

  According to Patent Document 1, a technique is proposed in which a semiconductor sensor and an impact sensor are provided in a radiation dose measuring device, and a signal output from the semiconductor sensor is invalidated when the impact sensor detects an impact.

  According to Patent Document 2, paying attention to the characteristic that the change in the number of radiation detection pulses in a certain measurement period is gentle, the predetermined measurement period is divided into two periods, and the pulses obtained in each period It has been proposed to distinguish between radiation detection pulses and noisy pulses by comparing the number with a constant.

JP 2007-285914 A Japanese Patent No. 3304785

  However, in the invention described in Patent Document 1, it is necessary to provide an impact sensor in addition to the semiconductor sensor in the radiation dose measuring device, which increases the radiation dose measuring device. Furthermore, since it is necessary to always make the impact sensors effective during measurement, it is difficult to save power in the radiation dose measuring apparatus.

  Further, in the invention described in Patent Document 2, when a radiation detection pulse and a noise pulse are generated at the same time or when a noise pulse is generated in two measurement periods, the noise detection pulse is also included in the radiation detection pulse. Since it counts, there is room for improvement in accuracy.

  Therefore, an object of the present invention is to make it possible to measure the radiation dose more accurately than in the past.

  The present invention includes, for example, detection means for detecting radiation, and identification means for identifying whether or not radiation has been detected based on the characteristics of an output signal output from the detection means. Providing equipment.

Further, the present invention includes, for example, a detection unit that detects radiation and outputs a detection signal;
The characteristics of the output signal output by the detection means, the characteristics of the radiation detection signal output when the detection means actually detects radiation, or the noise detection signal output when the detection means actually detects noise. Identifying means for comparing whether the output signal output by the detecting means is due to detection of radiation by comparing the characteristics;
Radiation dose measurement, comprising: a measurement unit that measures a radiation dose using the output signal when the identification unit identifies that the output signal is a signal resulting from detection of radiation. Providing equipment.

  According to the present invention, it is possible to detect radiation more accurately than in the past by identifying whether or not radiation has been detected based on the characteristics of the output signal output by the detection means. . Further, according to another aspect of the present invention, the radiation detection pulse can be identified more accurately than in the past by comparing the characteristics of the radiation detection pulse or noise pulse with the characteristics of the detected pulse. It becomes possible to measure.

Block diagram showing functions of radiation dose measuring device The figure which shows the structure applicable to a comparison part Diagram showing operation of signal width detector Diagram showing the operation of the peak detector Figure showing a noisy pulse whose pulse duration does not meet the conditions Diagram showing noisy pulses whose peak values do not meet the conditions Flow chart showing operation of count unit The figure which shows the ring buffer which memorizes the occurrence frequency of the radiation detection pulse Flow chart showing the operation of the correction unit Diagram showing the number of estimated radiation detection pulses Flow chart showing the operation of the measurement unit The figure which shows an example of the table which memorized the combination of measurement time and a calibration constant The figure which shows operation | movement of the correction | amendment part in 2nd embodiment. The flowchart which shows operation | movement of the correction | amendment part in 2nd embodiment. Block diagram showing an example of a microcomputer system

<First embodiment>
In this embodiment, whether or not radiation has been detected is identified based on the characteristics of an output signal that is output upon detection of radiation. Specifically, when radiation is detected, radiation is output from a sensor. Note that there is a clear difference in waveform between the characteristics of the signal (radiation detection pulse) and the characteristics of the noise detection signal (noise pulse) output from the sensor when noise is detected. In other words, by comparing the characteristics of the output signal output from the sensor with the characteristics of the radiation detection pulse or noise pulse, whether the output signal output from the sensor is derived from radiation or noise Identify And since a dose is measured based on the output signal originating in a radiation, a measurement precision can be improved rather than before.

  FIG. 1 is a block diagram showing a plurality of functions applicable to the radiation dose measuring apparatus 100 according to the embodiment of the present invention. The radiation dose measuring apparatus 100 includes a radiation detection unit 10, a pulse identification unit 20, a calculation unit 30, and an output unit 40. The radiation detection unit 10 and the calculation unit 30 function as a measurement unit that measures the radiation dose for each measurement period T. The pulse identification unit 20 functions as an identification unit that identifies a pulse generated by the radiation detection unit 10 into a radiation detection pulse and a noise pulse. The calculation unit 30 also functions as a correction unit that performs correction processing by calculating the number of radiation detection pulses that cannot be counted when noise occurs. Thus, the present invention performs accurate radiation dose measurement.

  The radiation detection unit 10 includes a radiation sensor 11 and detects a radiation to generate a pulse. The radiation sensor 11 is a sensor that generates a change in current when it detects radiation. The radiation sensor 11 is, for example, a semiconductor sensor such as a semiconductor diode (photodiode). Moreover, the apparatus (scintillation detector) which combined the scintillator, the semiconductor sensor, or the photomultiplier tube, the Geiger Mueller counter tube, etc. may be sufficient. As described above, the radiation detection unit 10 functions as a detection unit that detects radiation and outputs a detection signal.

  The pulse identification unit 20 identifies a pulse generated by the radiation detection unit 10 and outputs a radiation detection signal (pulse) or a noise detection signal (pulse) based on the identification result. In other words, the pulse identification unit 20 is characterized by the characteristics of the output signal output by the radiation detection unit 10 and the characteristics of the radiation detection signal output when the radiation detection unit 10 actually detects radiation or the radiation detection unit 10 actually generates noise. Is compared with the characteristics of the noise detection signal output when the signal is detected, thereby functioning as an identification means for identifying whether the output signal output from the radiation detection unit 10 is caused by the detection of radiation. That is, if the feature of the output signal output by the radiation detection unit 10 is close to the feature of the radiation detection signal, the output signal is considered to be derived from radiation. Further, if the feature of the output signal output from the radiation detection unit 10 is close to the feature of the noise detection signal, the output signal is considered to be derived from noise. On the contrary, if the feature of the output signal output from the radiation detection unit 10 is not close to the feature of the radiation detection signal, the output signal is considered to be derived from noise. Further, if the feature of the output signal output from the radiation detection unit 10 is not close to the feature of the noise detection signal, the output signal is considered to be derived from radiation. If the characteristics of the output signal are analyzed in this way, it can be determined whether the output signal is derived from radiation or noise. The pulse identification unit 20 includes a comparison unit 21 that compares the characteristics of the pulse and a signal transmission unit 22 that transmits a detection signal corresponding to the comparison result.

  FIG. 2 is a diagram showing a configuration applicable to the comparison unit 21. The pulse (signal A) input from the radiation detector 10 is converted into a voltage by the amplifier 211 and amplified. The signal width detector 212 measures the time width (pulse duration or pulse width) w1 of the input pulse. That is, the signal width detector 212 functions as a pulse width measuring unit that measures the pulse width of the pulsed output signal output from the radiation detector 10.

FIG. 3 is a diagram showing the principle of measuring the pulse width. As shown in FIG. 3, the signal width detector 212 detects the rise and fall of the signal A by comparing the amplitude of the pulsed signal A with the reference voltage Vref. When the signal width detector 212 detects a rising edge, the signal width detector 212 starts a timer by interrupt processing and starts time measurement. In addition, when the signal width detector 212 detects a falling edge, the signal width detector 212 stops the timer by interrupt processing and ends the time measurement. Thereby, the time width w1 of the signal A is measured. The signal width detector 212 compares the time width w1 with a predetermined threshold time w0. The threshold time w0 is, for example, a time width of a pulse generated when radiation is actually incident on the radiation sensor 11. The pulse when radiation is incident differs for each individual radiation sensor product. Therefore, if the value calibrated for each radiation sensor is set as the threshold time w0, the measurement accuracy of the dose will be further improved. In general, when an impact noise when a semiconductor sensor is used as the radiation sensor 11 is taken as an example, the time width of the noisy pulse is greatly increased as compared with the time width of the radiation detection pulse. Therefore, when the radiation sensor 11 detects radiation, the measured time width w1 is equal to or less than the threshold time w0 (w1 = <w0). At this time, the signal width detector 212 outputs the signal B. On the other hand, when the radiation sensor 11 detects noise, the measured time width w1 exceeds the threshold time w0 (w0 <w1). Therefore, the signal width detector 212 does not output the signal B. As described above, the signal width detector 212 also functions as a pulse width comparison unit that compares the pulse width measured by the pulse width measurement unit with a predetermined pulse width threshold. further,
FIG. 4 is a diagram for explaining a peak value which is one of the characteristics of the pulse. Generally, the peak value of the amplitude of the radiation detection pulse falls within a certain range. Therefore, if the peak value is within a certain range, the pulse can be determined as a radiation detection pulse.

  As shown in FIG. 4, the peak detector 213 detects the peak value PA of the signal A, and compares the peak value PA with a predetermined upper limit threshold PU and lower limit threshold PL. If the peak value PA is less than the upper threshold PU and exceeds the lower threshold PL (that is, PL <PA <PU), the signal A is a radiation detection pulse. Therefore, the peak detector 213 outputs a signal C which means that a pulse derived from radiation has been detected. If the peak value PA is not less than the upper threshold PU (PU = <PA), that is, if the peak value PA is equal to or higher than the upper threshold PU, the signal A is a noisy pulse. Similarly, when the peak value PA does not exceed the lower limit threshold PL (PA = <PL), that is, when the peak value PA is equal to or lower than the lower limit threshold PL, the signal A is a noise pulse. Therefore, the peak detector 213 does not output a signal C indicating that a pulse derived from radiation has been detected.

  In addition, the range which can take the peak value of a pulse when detecting radiation for every individual product of the radiation sensor 11 may differ. Therefore, by setting values calibrated for each individual product of the radiation sensor 11 as the upper threshold PU and the lower threshold PL, noise detection accuracy is improved, so dose measurement accuracy will also be improved.

  As described above, the peak detector 213 includes a peak value measuring unit that measures the peak value of the pulsed output signal output from the radiation detection unit 10, the peak value measured by the peak value measuring unit, and a predetermined peak value threshold value. Functions as a peak value comparison means.

  The signal transmission unit 22 shown in FIG. 1 determines whether the pulse (signal A) generated by the radiation sensor 11 is a radiation detection pulse derived from the incidence of radiation based on the signals B and C output from the comparison unit 21. A signal (pulse) that finally indicates whether the pulse is a noisy pulse is output to the arithmetic unit 30. That is, the signal transmission unit 22 may identify whether or not the output signal output from the radiation detection unit 10 is due to detection of radiation based on the comparison result of the pulse width. Moreover, the signal transmission part 22 may identify whether the output signal which the radiation detection part 10 output based on the comparison result of a peak value originates in having detected the radiation. Furthermore, the signal transmission unit 22 may identify whether or not the output signal output from the radiation detection unit 10 is due to detection of radiation based on the comparison result of the pulse width and the comparison result of the peak value. .

  For example, when there is a change in the signal A from the radiation sensor 11 and both the signal B of the signal width detector 212 and the signal C of the peak detector 213 are output, the radiation sensor 11 detects radiation. doing. Therefore, the signal transmission unit 22 outputs a radiation detection pulse (signal D). On the other hand, when there is a change in the signal A, the radiation sensor 11 detects noise if either or both of the signal B of the signal width detector 212 and the signal C of the peak detector 213 are not output. doing. Therefore, the signal transmission unit 22 outputs a noisy pulse (signal E).

  5 and 6 show an example of pulses output from the radiation sensor 11. Since the peak value PA of the pulse as seen in FIG. 5 is less than the upper threshold PU and exceeds the lower threshold PL, the pulse condition derived from radiation is satisfied. However, since the pulse time width W1 is longer than the threshold time W0, the condition of the pulse derived from radiation is not satisfied. Therefore, the pulse is determined to be a noise pulse from the comprehensive determination of the peak value and the pulse width. The time width W1 of the pulse as seen in FIG. 6 satisfies the pulse condition derived from radiation. However, the peak value PA of the pulse does not satisfy the condition. Therefore, the pulse is determined to be a noise pulse from the comprehensive determination of the peak value and the pulse width.

  Here, for the sake of more accuracy, comprehensive judgment of the peak value and the pulse width is executed. However, the identification processing may be executed only by the peak value, or the identification processing may be executed only by the pulse width. May be executed.

  When the pulse identification unit 20 identifies that the output signal is a signal resulting from the detection of radiation, the calculation unit 30 illustrated in FIG. 1 serves as a measurement unit that measures the radiation dose using the output signal. Function. The calculation unit 30 includes a count unit 31, a correction unit 32, and a measurement unit 33. The counting unit 31 is a unit that counts the occurrence of radiation detection pulses at regular intervals and stores them in a buffer. The correction unit 32 functions as a correction unit that corrects the number or dose of radiation detection pulses measured during a period in which noise is generated. When the pulse identification unit 20 identifies that the signal A output from the radiation sensor 11 is a signal resulting from the detection of radiation, the measurement unit 33 measures the radiation dose using the output signal. Function as.

  FIG. 7 is a flowchart showing the operation of the counting unit 31 of the calculation unit 30.

  In S <b> 701, the count unit 31 determines whether or not the signal D indicating that the radiation detection pulse has been detected is output from the signal transmission unit 22. If the signal D is confirmed, the process proceeds to S702. If the signal D cannot be confirmed, the process stays in S701. When the operation of the count unit 31 is realized by a microcomputer or the like, the subsequent process may be performed by generating an interrupt process when the signal D is received.

  In S702, the count unit 31 reads a pointer P indicating a buffer, which is a storage area for storing the number of occurrences of radiation detection pulses.

  FIG. 8 is a diagram illustrating an example of a buffer that stores the number of occurrences of radiation detection pulses. Here, a ring buffer 800 having N storage areas will be described. The count unit 31 records the number of occurrences of the radiation detection pulse for each sample time S, that is, the count unit 31 stores the number of occurrences in the ring buffer 800 as shown in FIG. Thus, the number of occurrences is the number of radiation detection pulses detected during the sample time S. Count unit 31 includes a timer in addition to ring buffer 800. The count unit 31 measures the sample time S with a timer. Then, the count unit 31 increments the pointer P by one for each predetermined sample time S.

  The ring buffer 800 may be an array of general integer type variables. In this case, the pointer P indicates each element of the array. Let T be the measurement time required for one measurement of radiation dose. In this case, the number N of elements is T / S. For example, it is assumed that the measurement time of radiation dose (time required for calculating the radiation dose) is 60 seconds, and the number of occurrences of radiation detection pulses is recorded every second. That is, since T = 60 seconds and S = 1 second, the ring buffer 800 is an array having 60 elements.

In S703, the count unit 31 reads the numerical value I _P stored in the buffer indicated by the read pointer P, increments the numerical value I _P, overwriting. Thereafter, the processing returns to S701, and the counting unit 31 repeats the processes of S701 to S703.

  FIG. 9 is a flowchart showing the operation of the correction unit 32 of the calculation unit 30.

  In step S <b> 901, the correction unit 32 determines whether a signal E indicating that a noisy pulse has been detected is output from the signal transmission unit 22. If the signal E cannot be recognized, the process stays at S901. If the signal E can be confirmed, the process proceeds to S902.

  In step S902, the correction unit 32 reads a pointer P indicating a buffer that is a storage area for storing the number of occurrences of radiation detection pulses.

  In S903, the correction unit 32 measures the duration N of the noise pulse. As a method of measuring the duration N of the noisy pulse, for example, a method similar to the method of measuring the time width W1 of the input pulse in the signal width detector 212 in the comparison unit 21 of the pulse identification unit 20 is applied. This can be achieved. Alternatively, the time width W1 may be adopted as the duration N as it is.

  In S904, the correction unit 32 artificially calculates the number of occurrences (counts) of radiation detection pulses that are assumed to have occurred during the duration N of the noisy pulse. Here, attention is paid to the characteristic that there is no sudden change in the number of times radiation is incident on the radiation sensor 11 during a period in which noise such as impact noise is detected and a period in which noise is not detected. As a result, the number of occurrences of radiation detection pulses during the period in which noise is detected is the same as that in the period in which noise is not detected (noise non-detection period). Approximately obtained from the number of pulse generations. For example, the noise non-detection period is a noise non-detection period immediately before the noise detection period or a noise non-detection period immediately after the noise detection period. There may be one or more noise non-detection periods used for correction.

  The method that can calculate the number of radiation detection pulses assumed to have occurred during the noise detection period at the highest speed is complemented by using the number of radiation detection pulses measured in the noise non-detection period immediately before or after the noise detection period. Would be the method.

FIG. 10 is a diagram illustrating an example of a method for complementing the number of occurrences of radiation detection pulses. For example, assume that the sample time S is 1 second and the duration N of the noisy pulse is 2 seconds. In this case, the number of radiation detection pulses in 2 seconds immediately before the occurrence of noise is “3”, which is the value _IP-2 stored in the buffer indicated by the pointer P-2, and the buffer indicated by the pointer P-1. Is "6" obtained by adding "3" which is the value _IP-1 stored in. The correction unit 32 sets this as the number of occurrences of the radiation detection pulse estimated to have occurred during the duration N of the noisy pulse. Similarly, the correction unit 32 may be a noise non-detection period that is located immediately after a period in which noise is generated, and may use the number of radiation detection pulses measured in a period having the same length as the duration N. Good. That is, the correction unit 32 may complement the value by adding the values stored in the buffers indicated by the pointers P + 2 and P + 3. Further, the correction unit 32 may complement the value by adding the values stored in the buffers indicated by the pointers P-1 and P + 2. Further, linear interpolation may be executed. The correcting unit 32 may add the values stored in the buffers indicated by the pointers P-2, P-1, P + 2, and P + 3, and obtain the average value.

Further, the correction unit 32 uses the value I _P-1 stored in the buffer indicated by the pointer P-1 indicating the period immediately before the period corresponding to the pointer P, which can be the time when the noise is generated, as a pointer. The number of times corresponding to the period of P may be calculated. In this case, it is estimated that _IP-1 radiation detection pulses are generated for each sample time S in the duration N of the noisy pulse. Therefore, the number of radiation detection pulses estimated to have occurred during the duration N is calculated by the following equation.

N * _IP-1 / S
For example, this estimation method is applied to the case shown in FIG. The sample time S is 1 second, and the duration N of the noisy pulse is 2 seconds. The value I _P-1 pointer P-1 is stored in the buffer shown is "3". Therefore, when these numerical values are substituted into the above formula, the number of estimations is six. Similarly, it may be calculated using the number of radiation detection pulses in a period immediately after a period in which noise is detected.

In order to increase the accuracy when the sample time S is set short, for example, each buffer indicated by each pointer using a plurality of pointers P-1, P-2, P-3, etc. In other words, values obtained by reading out I _P-1 , I _P-2 , and _IP-3 and averaging them may be used. As a result, it is possible to calculate by expanding the period in which noise immediately before noise is not detected. However, in the case where the sample time S is set to be long, the number of occurrences at the time when the pointer is decremented from the period in which noise is detected is included every time the pointer is decremented. Therefore, in order to maintain accuracy, it is necessary to set a period used for correction so as to be within an appropriate time range. Similarly, when estimation is performed using the number of occurrences in a period immediately after a period in which noise is detected, a value in a period in which the time range is expanded may be used for calculation. In this case, a plurality of pointers P + 2, P + 3, P + 4 may be used.

  In S905, the correction unit 32 writes the estimated number of occurrences of the radiation detection pulse (the number of estimated radiation detection pulses) in the buffer indicated by the pointer P, which is the point in time when noise is detected. If the duration N of the noise pulse is shorter than the sample time S at this time, the number of radiation detection pulses generated during the period until the noise is generated is already stored in the buffer indicated by the pointer P. there will be. In this case, the correction unit 32 may cumulatively add the number of estimated radiation detection pulses to the numerical value in order to make it an error on the safety side from the standpoint of safety of radiation protection.

  As shown in FIG. 10, when the duration N of the noisy pulse does not fall within the sample time S, there are a plurality of buffers in which no radiation detection pulse is stored. The correction unit 32 may equally distribute by obtaining an average value obtained by dividing the estimated number of occurrences of radiation detection pulses by the number of those buffers, and store the average value in each buffer. In the example shown in FIG. 10, since there are two buffers corresponding to the duration N, “6” that is the estimated value is divided by “2”, and “3” is stored in each.

  FIG. 11 is a flowchart showing the operation of the measurement unit 33 of the calculation unit 30.

  In S1101, the measurement unit 33 executes initialization of buffers and variables, setting of a timer for measuring the measurement period T, and the like as initial settings. A counter may be employed instead of the timer.

  In S1102, the measurement unit 33 acquires the elapsed time t measured by the timer and determines whether the measurement period T has elapsed. For example, when the measurement period T for one measurement of radiation dose is 60 seconds, the measurement unit 33 performs the next measurement after the measurement period T has elapsed. That is, the measurement unit 33 determines whether or not the elapsed time t from the start of radiation detection exceeds the measurement period T. Using the measurement period T as a unit, the radiation detection unit 10 detects radiation, and the count unit 31 accumulates the number of radiation detection pulses. The calculation of the radiation dose is executed every measurement period T. That is, the measurement period T is a time interval for executing processing for radiation dose measurement. Until the elapsed time t exceeds the measurement period T, the operation of the dose measurement unit involved in the calculation of the radiation dose in the measurement unit 33 may be stopped. This is to reduce power consumption as much as possible. The counter or timer provided in the measuring unit 33 may be the same as that used for measuring the sample time S in the counting unit 31. The measurement unit 33 uses these to measure the elapsed time t from the start of radiation detection (the elapsed time t since the dose calculation unit involved in the calculation of the radiation dose is stopped). The measurement unit 33 monitors whether or not the elapsed time t exceeds the measurement period T. If the elapsed time t exceeds the measurement period T, the process proceeds to S1103. By the way, the pointer P points to a storage area (element) of the ring buffer 800. Therefore, the pointer P is incremented every sample time S and indicates the head of the buffer after the measurement period T has elapsed. Therefore, the measurement unit 33 may recognize the passage of the measurement period T by monitoring the timing at which the pointer P is initialized so as to point to the head of the buffer.

  In S <b> 1103, the measurement unit 33 reads the number k of radiation detection pulses stored by the counting unit 31. The count unit 31 stores a value obtained by accumulatively adding the numerical values stored in each element in the ring buffer 800 shown in FIG. 8, that is, the number k of radiation detection pulses. The measuring unit 33 assigns the read pulse number k to the buffer variable K.

  In S <b> 1104, the measurement unit 33 obtains the radiation dose by multiplying a buffer variable K indicating the number of detections (number of pulses) of radiation detected during the measurement period T by a predetermined calibration constant. The radiation dose may be an air dose (nGy) or an absorbed dose (μSv). Examples of the calibration constant include a calibration constant X corresponding to the configuration of the radiation sensor 11 and a calibration constant Y corresponding to the measurement period T. Since the configuration of the radiation sensor 11 is determined at the design stage, the calibration constant X is stored in a ROM or the like provided in the measurement unit 33. Note that the measurement period T may be constant or dynamically changed. When the measurement period T is constant, the calibration constant Y as well as the calibration constant X is stored in the ROM of the measurement unit 33 or the like. When the measurement period T is changed, the calibration constant Y also changes dynamically. As a method for obtaining the calibration constant Y corresponding to the measurement period T, a mathematical formula may be used, or a table 1200 as shown in FIG. 12 may be used. In the table 1200, the measurement periods T and calibration constants Y for all combinations may not be registered. In this case, an unregistered calibration constant Y may be calculated by linear interpolation. The dose calculation unit of the measurement unit 33 obtains the radiation dose using the following formula and substitutes it into the buffer variable R.

R = K, X, Y
In S1105, the measurement unit 33 issues an output command for outputting the contents of the buffer variable R indicating the calculated radiation dose to the output unit 40, and causes the display notification unit 41 of the output unit 40 to output the radiation dose. The output unit 40 displays the measured radiation dose or outputs a warning sound according to the output command. The display notification unit 41 is a display device that displays the radiation dose, and is, for example, a liquid crystal display or a self-luminous display. The voice notification unit 42 compares the radiation dose obtained by the measurement unit 33 in the calculation unit 30 with a predetermined threshold, and outputs a warning by voice to the user when the radiation dose exceeds the predetermined threshold. Good. The sound notification unit 42 may be a sound generation device such as a buzzer. When receiving the output command, the display notification unit 41 reads the buffer variable R indicating the radiation dose and displays the radiation dose. When the voice notification unit 42 receives the output command, the voice notification unit 42 compares the buffer variable R indicating the radiation dose with a predetermined threshold value Z. If the buffer variable R exceeds the threshold value Z, the voice notification unit 42 outputs a warning sound or warning voice. Output. If not exceeded, the voice notification unit 42 does not output a warning sound or warning voice. The threshold value Z is stored in the ROM of the output unit 40, the ROM of the calculation unit 30, or the like.

<Second embodiment>
The correction unit 32 according to the first embodiment calculates the number of radiation detection pulses in the period in which noise is detected immediately before or immediately after the period in which noise is detected as the number of radiation detection pulses in the period in which noise is detected. It was estimated using. On the other hand, the time N during which noise is detected is not included in the measurement period T of the radiation dose, and the radiation dose at the time when noise is detected is compensated by performing additional measurement for the corresponding time N by correction processing. Is also possible.

  FIG. 13A is a diagram for explaining the measurement method of the first embodiment. FIG. 13B is a diagram for explaining a measurement method according to the second embodiment. As shown in FIG. 13A, the noise detection pulse generation count is not accumulated for the noise duration N in the measurement period T. Therefore, in the first embodiment, it is necessary to estimate the number of radiation detection pulses generated during the noise duration N. On the other hand, the second embodiment is characterized in that the dose is measured by extending the measurement period T by the noise duration N as shown in FIG.

  FIG. 14 is a flowchart showing an operation applicable to the correction unit 32 according to the second embodiment. Here, it is assumed that no measurement results are accumulated for the sample time S when noise occurs or occurs during measurement for each sample time S.

  In S1401, the correction unit 32 determines whether the pulse identification unit 20 is transmitting a noisy pulse (signal E). Note that the processing in S1401 can proceed in the same manner as in S701, which is the operation of the counting unit 31. If the pulse identification unit 20 has transmitted a noisy pulse (signal E), in S1402, the correction unit 32 reads a pointer P indicating a buffer for storing the number of occurrences of the radiation detection pulse.

  In step S1403, the correction unit 32 stops incrementing the buffer pointer P once. The pointer P is incremented by one every sample time S by a timer. Therefore, by canceling the increment of the buffer pointer P once, the measurement period T is substantially extended by the sample time S.

  In S1404, the correction unit 32 initializes the contents of the buffer indicated by the pointer P.

  By these processes, the pointer P is not incremented as long as noise is detected. Therefore, the number of radiation detection pulses measured after noise is no longer detected is written into the buffer indicated by the pointer P. That is, the number of radiation detection pulses at the time when noise no longer occurs is overwritten on the buffer that is the storage destination of the number of radiation detection pulses at the time when noise occurs. In this way, the process of storing the number of radiation detection pulses in the period in which noise is occurring is skipped. In addition, it is not necessary to prepare a buffer for storing data measured at a time when noise is detected. That is, in the second embodiment, as in the first embodiment, it is sufficient to prepare a buffer for storing data measured during the measurement period T. Of course, a noise generation period (duration N) may be assumed in advance, and more buffers may be prepared accordingly. However, in this case, it is necessary to specify a buffer that stores data when noise occurs and to exclude the data stored in the buffer from the dose measurement.

  In the second embodiment, it is necessary to calculate the radiation dose by performing an extra measurement for the period during which noise is occurring (duration N). That is, as shown in FIG. 13B, it is necessary to measure by extending the measurement period T by the time N (or dynamically obtaining the calibration constant Y for the time obtained by subtracting the time N from the measurement period T. Thus, the radiation dose may be calculated when the measurement period T elapses without extending the measurement period T).

  The measuring unit 33 monitors the timing when the pointer P is initialized to the head of the buffer. When it is time to initialize the pointer P to the head of the buffer, the measurement unit 33 proceeds to a radiation dose calculation process. In this way, a simple process can be achieved. When noise is detected, time elapses without the pointer P being incremented. Therefore, the timing at which the pointer P is initialized to the head of the buffer means the time when the measurement period T and the noise detection time N have elapsed. Therefore, monitoring the timing at which the pointer P is initialized to the head of the buffer is equivalent to extending the measurement period T by the time N as a result. Of course, the measurement unit 33 may measure the time N during which noise is generated, and calculate the radiation dose after the sum of the measurement period T and the time N has elapsed. In that case, the time N can be obtained by measuring and accumulating the time width of the noisy pulse E by the same method as the operation in the signal width detector 212.

<Third embodiment>
Since the above-described functions of the present embodiment can be realized by a sensor or a logic circuit, a part that can be realized by a logic circuit may be realized by a CPU.

  FIG. 15 is a block diagram of a general microcomputer system. The CPU 50 comprehensively controls each unit and executes necessary arithmetic processing. The ROM 51 is a storage unit that stores a control program and the like. The RAM 52 is a work memory and is a storage unit that stores various variables and flags. The input device 53 is a keyboard, a switch, a touch panel, or the like. The display device 54 displays data such as radiation dose. The audio output device 55 is a buzzer that outputs a warning sound, an audio output circuit that outputs audio, a speaker, and the like.

  CPU50 implement | achieves the function which can be performed with a logic circuit among the functions mentioned above by running a control program. For example, the CPU 50 realizes a part that executes the logical operation of the arithmetic unit 30. The procedures included in the control program executed by the CPU 50 are as shown in FIG. 7, FIG. 9, FIG. 11, and FIG.

  Incidentally, the radiation dose measuring apparatus 100 may include a communication unit that communicates with an external information processing apparatus (computer). Thereby, the radiation dose measuring apparatus 100 can transmit the radiation dose information to the computer. The radiation dose measuring apparatus 100 may store the accumulated value of the exposure dose in a memory backed up by a battery, an EEPROM, or a flash memory (registered trademark). Thereby, the radiation dose measuring apparatus 100 may continuously manage the radiation dose by continuously accumulating the radiation dose.

  In order to further improve the noise detection accuracy, a noise sensor 56 such as an impact sensor, a vibration sensor, or an electromagnetic sensor that detects noise such as an external radio wave or a vibration shock that interferes with radiation detection in the radiation sensor 11 may be provided. Good. The CPU 50 may determine whether noise is generated by using the noise sensor 56 and generate the signal D and the signal E. The noise sensor 56 may be used in place of the pulse identification unit 20 or may be used together with the pulse identification unit 20. When both the noise sensor 56 and the pulse identification unit 20 are used, a logical sum or a logical product of signals output from the noise sensor 56 and the pulse identification unit 20 may be output to the arithmetic unit 30.

  As described above, according to the present embodiment, the radiation detection pulse can be identified more accurately than in the past by comparing the characteristics of the radiation detection pulse or the noise pulse with the characteristics of the detected pulse. Can be measured accurately. For example, the pulse width (pulse duration) or the peak value of the pulse may be adopted as a feature of the radiation detection pulse or noise pulse. For example, the pulse identification unit 20 compares the pulse width with a predetermined pulse width threshold, and identifies whether the signal output from the radiation detection unit 10 is due to detection of radiation based on the comparison result. Also good. Similarly, the pulse identification unit 20 compares the peak value of the pulsed output signal with a predetermined peak value threshold, and the signal output from the radiation detection unit 10 based on the comparison result is due to the detection of radiation. You may identify whether it is a thing or not. Furthermore, the pulse identification unit 20 may identify whether the signal output from the radiation detection unit 10 is due to detection of radiation based on the comparison result of the pulse width and the comparison result of the peak value. The configuration of the pulse identification unit 20 can be simplified if noise identification is performed by using only the pulse width or the peak value. On the other hand, if noise identification is performed using both the pulse width and the peak value, the identification accuracy will be improved.

  According to the present embodiment, the correction unit 32 improves the dose measurement accuracy by correcting the dose measured during a period in which noise is generated. For example, the correction unit 32 may correct a dose measured during a period in which noise is generated using a dose measured in a period in which noise is not generated. Further, the correction unit 32 corrects the dose measured during the period in which the noise is generated using the dose measured in the period in which no noise is adjacent to the period in which the noise is generated. Also good. In particular, it has been empirically known that the measurement results have a certain degree of correlation between the period in which noise is generated and the adjacent period. Therefore, the dose in the period in which the noise is generated can be accurately estimated by obtaining the dose in the period in which the noise is generated from the dose in the adjacent period.

  As described in the second embodiment, out of the doses measured every predetermined measurement period T, the doses measured during the period in which noise occurred (noise duration N) are excluded, and the noise duration time Measurement may be performed by extending the measurement period T by the same length as N. In this case, although the time from the start of measurement to the end of measurement is somewhat increased, the measurement accuracy can be improved.

Claims (9)

Detection means for detecting radiation;
A radiation dose measuring apparatus comprising: an identification unit that identifies whether or not radiation has been detected based on a feature of an output signal output from the detection unit. Detection means for detecting radiation and outputting a detection signal;
The characteristics of the output signal output by the detection means, the characteristics of the radiation detection signal output when the detection means actually detects radiation, or the noise detection signal output when the detection means actually detects noise. Identifying means for comparing whether the output signal output by the detecting means is due to detection of radiation by comparing the characteristics;
Radiation dose measurement, comprising: a measurement unit that measures a radiation dose using the output signal when the identification unit identifies that the output signal is a signal resulting from detection of radiation. apparatus. The identification means includes
Pulse width measuring means for measuring the pulse width of the pulsed output signal output by the detecting means;
Pulse width comparing means for comparing the pulse width measured by the pulse width measuring means with a predetermined pulse width threshold;
Have
The said identification means identifies whether the output signal output from the said detection means originates in having detected the radiation based on the comparison result of the said pulse width comparison means. Radiation dose measuring device. The identification means includes
Peak value measuring means for measuring the peak value of the pulsed output signal output by the detecting means;
A peak value comparing means for comparing the peak value measured by the peak value measuring means with a predetermined peak value threshold;
Have
The said identification means identifies whether the output signal output from the said detection means originates in having detected the radiation based on the comparison result of the said peak value comparison means. Radiation dose measuring device. The identification means includes
Pulse width measuring means for measuring the pulse width of the pulsed output signal output by the detecting means;
Pulse width comparing means for comparing the pulse width measured by the pulse width measuring means with a predetermined pulse width threshold;
Peak value measuring means for measuring the peak value of the pulsed output signal output by the detecting means;
A peak value comparing means for comparing the peak value measured by the peak value measuring means with a predetermined peak value threshold;
Have
The identification means identifies whether the output signal output from the detection means is due to detection of radiation based on the comparison result of the pulse width comparison means and the comparison result of the peak value comparison means. The radiation dose measuring apparatus according to claim 2, wherein   The radiation dose measuring apparatus according to claim 2, further comprising a correcting unit that corrects a dose measured by the measuring unit during a period in which noise is generated.   7. The radiation dose measurement according to claim 6, wherein the correction unit corrects a dose measured during a period in which noise is generated, using a dose measured in a period in which noise is not generated. apparatus.   The correction means corrects a dose measured during a period in which noise is generated using a dose measured in a period in which no noise is adjacent to the period in which the noise is generated. The radiation dose measuring apparatus according to claim 7. The measuring means is means for measuring a dose every predetermined measurement period,
The correction means excludes a dose measured during a period in which noise has occurred among the doses measured in the measurement period, and extends the measurement period by the same length of the period in which the noise occurs. The radiation dose measuring apparatus according to claim 6, wherein the measurement is performed.