JP2014020901A - Radiation measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the detecting efficiency of radiation even when any distortion is generated in a scintillation fiber.SOLUTION: A radiation measurement device is configured such that a measurement system 2 constituted of photo-detectors 5a and 5b, amplifiers 6a and 6b, discriminators 7a and 7b, a time-to-pulse height converter 8 for detecting the incident position of a radiation in the longitudinal direction of a scintillation fiber 1 and a multi-channel analyzer 10 for searching the spatial distribution of radiation dose following the longitudinal direction of the scintillation fiber 1 is connected to the scintillation fiber 1. The radiation measurement device includes stain measurement means 3 for measuring the distortion amounts of the scintillation fiber 1 by a stain gauge 11 attached to the scintillation fiber 1 and an adjustment device 4 for inputting the measurement result. The adjustment device 4 adjusts the noise-cut threshold of the discriminators 7a and 7b of the measurement system 2 by expecting the attenuation of scintillation lights due to the distortion of the scintillation fiber 1.

Description

  The present invention relates to a radiation measuring apparatus of a type provided with a scintillation fiber.

  As one of the radiation measurement methods, a method using a scintillation fiber that generates scintillation light by the incidence of radiation has been proposed. This is based on the ratio of the number of photons (attenuation ratio) and the arrival time difference when the scintillation light generated by the incidence of radiation reaches one end and the other end of the scintillation fiber. Along with this, the distribution of the air dose is measured (see, for example, Non-Patent Document 1, Patent Document 1, and Patent Document 2).

Japanese Patent No. 3003843 Japanese Patent No. 3309728

Tetsuo Torii, “Radiation Distribution Measurement Using Optical Fiber”, Radioisotope (RADIOISOTOPES), Japan Isotope Association, 1995, Vol. 44, No. 7, p. 69-70

  However, when the scintillation fiber is bent and distorted, the transmission characteristic of the scintillation light changes so that attenuation is increased in the portion where the distortion occurs. Therefore, when the scintillation fiber is distorted, the amount of attenuation until the scintillation light generated by the incidence of radiation reaches one end side and the other end side of the scintillation fiber increases. Will become weaker.

  Therefore, in this case, if noise is separated from the radiation detection signal using a discriminator in which a certain noise cut threshold is set, detection of radiation weakened due to the influence of the scintillation fiber distortion There is a possibility that the signal becomes smaller than the noise cut threshold and is buried in noise.

  Therefore, when the scintillation fiber is distorted as described above, the detection efficiency of the radiation is lowered. In addition, the statistical accuracy of air dose measurement is lowered, and the measurement time is increased.

  Therefore, the present invention provides a radiation measuring apparatus capable of increasing the radiation detection efficiency by enabling detection without being buried in noise even when the radiation detection signal becomes weak due to the influence of the distortion of the scintillation fiber. It is something to be offered.

  In order to solve the above problems, the present invention comprises a scintillation fiber and a measurement system for the scintillation fiber corresponding to claim 1, the measurement system including a photodetector connected to the scintillation fiber, the light An amplifier for amplifying the radiation detection signal output from the detector, a discriminator for removing noise from the detection signal amplified by the amplifier by a noise cut threshold, and a detection signal input via the discriminator Based on the above, a time-wave height converter for detecting the incident position of the radiation in the longitudinal direction of the scintillation fiber, and a multichannel analyzer for obtaining a spatial distribution of the radiation dose along the longitudinal direction of the scintillation fiber, Strain measuring means for detecting the strain of the scintillation fiber and the strain meter Based on the measurement results of the distortion amount of the scintillation fiber is measured by means a structure comprising an adjustment device for adjusting the noise-cut threshold discriminator of the measurement system.

  In the above configuration, the adjustment device has a function of issuing an alarm when the noise cut threshold value of the discriminator is set and the set value of the noise cut threshold value is lower than a preset allowable level. The configuration is as described above.

  Further, in each of the above-described configurations, the measurement system includes a storage unit, and the storage unit has a radiation dose position at each of the plurality of scintillation fibers where distortion is present using a standard dose. It is possible to memorize the correlation between the radiation incident position in the longitudinal direction of the scintillation fiber and the counting off of the radiation count value obtained by simulating the operation of the scintillation fiber. Based on the detection result of the incident position and the correlation between the radiation incident position in the longitudinal direction of the scintillation fiber stored in the storage means and the count value of the count value of the radiation, the count value of the count value is compensated. After the correction, the radiation dose with respect to the longitudinal direction of the scintillation fiber is calculated based on the corrected radiation count value. The way the configuration includes a function of obtaining between distribution.

  In each configuration described above, the strain measuring means includes a strain gauge attached to the scintillation fiber.

  Similarly, in each of the above-described configurations, the strain measuring means includes an optical fiber strain sensor attached along the scintillation fiber.

According to the radiation measuring apparatus of the present invention, the following excellent effects are exhibited.
(1) Even when the scintillation fiber is distorted and the scintillation light reaching the photo detector of the measurement system is attenuated, the radiation detection signal output from the photo detector becomes weak. It is possible to prevent the detection signal from being buried in noise.
(2) Thereby, even when the scintillation fiber is distorted, the radiation detection efficiency can be increased. For this reason, the time-wave height converter of the measurement system can satisfactorily detect the radiation incident position in the longitudinal direction of the scintillation fiber. In the multichannel analyzer, the statistical accuracy of the measurement result of the spatial distribution of the radiation dose along the longitudinal direction of the scintillation fiber can be improved.
(3) Further, it is possible to shorten the measurement time required to obtain the measurement result of the spatial distribution of the radiation dose by the multichannel analyzer.

It is a schematic diagram showing one embodiment of a radiation measuring device of the present invention. It is a schematic diagram which shows the other form of implementation of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of the radiation measuring apparatus of the present invention.

  That is, the radiation measuring apparatus according to the present invention is indicated by reference numeral I in FIG. 1, and the scintillation fiber 1 serving as a radiation detection unit, the measurement system 2 connected to the scintillation fiber 1, and the distortion of the scintillation fiber 1 are measured. Based on the strain measurement means 3 to be detected and the measurement result of the strain amount of the scintillation fiber 1 measured by the strain measurement means 3, an adjustment device 4 such as a computer for adjusting the measurement system 2 of the scintillation fiber 1 is provided. Prepare.

  The scintillation fiber 1 measuring system 2 includes photodetectors 5 a and 5 b such as photomultiplier tubes attached to both ends of the scintillation fiber 1.

  Further, each of the photodetectors 5a and 5b has amplifiers 6a and 6b and a discriminator 7a on the output side for outputting a radiation detection signal (hereinafter simply referred to as a detection signal) as an electrical signal when the scintillation light is incident. , 7b, the time-wave height converter 8 is connected.

  A signal delay circuit 9 is provided between one of the discriminators 7 a and 7 b and the time-wave height converter 8.

  A multi-channel analyzer 10 is connected to the time-wave height converter 8. Further, the adjusting device 4 is connected to the multi-channel analyzer 10.

  Note that the delay of the detection signal by the signal delay circuit 9 is such that the radiation signal is detected by the other photodetector 5b even when radiation enters the vicinity of the one photodetector 5a in the longitudinal direction of the scintillation fiber 1. Is set to be input to the time-wave height converter 8 prior to the detection signal of the one photodetector 5a.

  Thereby, in the measurement system 2, when radiation is incident on any part of the scintillation fiber 1 to generate scintillation light, the scintillation light is detected by the photodetectors 5a and 5b. Detection signals are output from the photodetectors 5a and 5b. The detection signals are amplified by the corresponding amplifiers 6a and 6b, and then input to the corresponding discriminators 7a and 7b.

  In each of the discriminators 7a and 7b, after the noise is removed from the detection signal by a noise cut threshold set by the adjusting device 4 as described later, the noise is then removed. The detection signal is input to the time-wave height converter 8. At this time, since the signal delay circuit 9 is provided, the detection signal from the other photodetector 5b is sent to the time-wave height converter 8 before the detection signal from the one photodetector 5a. It will be entered.

  The time-wave height converter 8 detects a time difference from the time when the detection signal by the other photodetector 5b is input to the time when the detection signal by the one photodetector 5a is input, and this time difference is detected. From the delay time set in the signal delay circuit 9, the time difference when the scintillation light first reaches the photodetectors 5a and 5b is obtained, and from this time difference, the length of the scintillation fiber 1 is determined. The incident position of the radiation in the direction is detected.

  Furthermore, since the wave height at that time is proportional to the count value (count) of the radiation, the input channel height spectrum is analyzed by the multi-channel analyzer 10 to obtain the radiation dose with respect to the longitudinal direction of the scintillation fiber 1. The spatial distribution is obtained.

  The strain measuring means 3 includes a strain gauge 11 as a strain sensor attached to the scintillation fiber 1 and a strain measuring device 12 to which the strain gauge 11 is connected.

  The strain gauges 11 are, for example, arranged at a plurality of locations spaced apart in the longitudinal direction of the scintillation fiber 1, and the strain gauges 11 are respectively attached to corresponding locations of the scintillation fiber 1. Each strain gauge 11 is connected to a common strain measuring device 12.

  As a result, the strain measuring device 12 can measure the amount of strain generated at each attachment point of the strain gauge 11 in the scintillation fiber 1 in real time based on the signals input from the strain gauges 11. It is. Further, the distortion measuring device 12 can output the measurement result of the distortion amount to the adjusting device 4.

  When the adjustment device 4 receives the measurement result of the strain amount of the scintillation fiber 1 from the strain measurement device 12, the adjustment device 4 calculates the optimum noise cut threshold values of the discriminators 7a and 7b based on the measurement result. I have to do it.

  A specific method for calculating the noise cut threshold by the adjusting device 4 is as follows.

  That is, the scintillation fiber 1 has a different correlation between the amount of distortion generated in the scintillation fiber 1 and a change in transmission characteristics in which the scintillation light is attenuated depending on the type, thickness, length, and the like.

  Therefore, in the radiation measuring apparatus I of the present invention, an experiment is performed in advance to examine the attenuation of scintillation light generated when a certain amount of distortion is applied to the scintillation fiber 1 using the actual scintillation fiber 1. The correlation between the amount of distortion generated in the fiber 1 and the change in the transmission characteristic of the scintillation light is obtained, and the obtained correlation is stored as a correlation table or a correlation coefficient in a storage unit (not shown) of the adjustment device 4. I have to do it.

  By the way, in the scintillation fiber 1, the transmission path until the scintillation light generated at the position reaches one end side and the other end side of the scintillation fiber 1 differs depending on the position where the radiation is incident. In view of this, the adjustment device 4 uses the distortion amount of the scintillation fiber 1 as a representative value measured by the distortion measurement means 3 as a representative value, and changes in the transmission characteristics of the scintillation light of the scintillation fiber 1 described above. It is assumed that the correlation is obtained.

  In the adjustment device 4, when the measurement result of the strain amount of the scintillation fiber 1 is input from the strain measurement device 12, first, based on the correlation table and the correlation coefficient stored in the storage unit (not shown), A transmission characteristic of the scintillation light in the state of the measured strain amount of the scintillation fiber 1 is obtained.

  Next, the adjusting device 4 estimates the attenuation that the scintillation light receives before reaching the photodetectors 5a and 5b based on the transmission characteristics obtained as described above, and the estimated attenuation is calculated. The scintillation light after receiving is incident on the photodetectors 5a and 5b, so that the detection signals output from the photodetectors 5a and 5b are amplified by the corresponding amplifiers 6a and 6b. Is calculated.

  Thereafter, the adjustment device 4 is configured to issue a command to set a signal intensity slightly lower than the intensity of the amplified detection signal calculated based on the scintillation light after receiving the estimated attenuation as the noise cut threshold. Each discriminator 7a, 7b is provided.

As a result, in each of the discriminators 7a and 7b, a noise cut threshold is set based on the command from the adjusting device 4.

  In addition, when setting the noise cut threshold value of the discriminators 7a and 7b by the adjusting device 4 based on the measurement result of the strain amount of the scintillation fiber 1 by the strain measuring device 12, the set value of the noise cut threshold value Is too low, it becomes difficult to separate the detection signal from noise. In this case, in the radiation measuring apparatus I of the present invention, it becomes impossible to accurately measure the distribution of the air dose along the longitudinal direction of the scintillation fiber 1. Therefore, in the adjustment device 4, when it is determined that the noise cut threshold value set in the discriminators 7a and 7b is lower than a preset allowable level and separation from noise becomes difficult, an alarm is generated. It has a function to emit.

  The radiation measuring apparatus I according to the present invention having the above configuration measures the amount of distortion in real time by the strain measuring means 3 when the scintillation fiber 1 is distorted when measuring radiation. Therefore, in the radiation measuring apparatus I of the present invention, each of the discriminators 7a and 7b in a state where the attenuation of scintillation light due to a change in transmission characteristics generated in the scintillation fiber 1 is expected according to the measurement result of the distortion amount. The noise cut threshold is set.

  Therefore, according to the radiation measurement apparatus I of the present invention, the scintillation fiber 1 is distorted, and the scintillation light reaching the photodetectors 5a and 5b is attenuated, whereby the photodetectors 5a and 5b. Even when the detection signal output is weaker, it is possible to prevent the detection signal from being buried in noise.

  As a result, the radiation measuring apparatus I of the present invention can increase the radiation detection efficiency even when the scintillation fiber 1 is distorted. For this reason, the time-wave height converter 8 of the measurement system 2 can satisfactorily detect the incident position of the radiation in the longitudinal direction of the scintillation fiber 1. Therefore, the multi-channel analyzer 10 can improve the statistical accuracy of the measurement result of the radiation dose spatial distribution along the longitudinal direction of the scintillation fiber 1.

  Furthermore, in the radiation measurement apparatus I of the present invention, it is possible to shorten the measurement time required to obtain the measurement result of the spatial distribution of the radiation dose by the multichannel analyzer 10.

  Next, FIG. 2 shows a modification of the embodiment of FIG. 1 as another embodiment of the present invention.

  That is, the radiation measurement apparatus according to the present embodiment has a strain measurement unit 3 attached to the scintillation fiber 1 in the same configuration as shown in FIG. Instead of a configuration comprising the strain measuring device 12, an optical fiber strain sensor 13 attached to the scintillation fiber 1 along the longitudinal direction, and a strain measuring device 12a connected to the optical fiber strain sensor 13; It is set as the structure provided with the distortion measurement means 3a of the structure which consists of these.

  Other configurations are the same as those shown in FIG. 1, and the same components are denoted by the same reference numerals.

  In the strain measuring means 3a, when the scintillation fiber 1 is distorted, the optical fiber strain sensor 13 is similarly distorted. Therefore, the strain measuring device 12a can detect the amount of distortion generated in the scintillation fiber 1 in accordance with the detection of the amount of distortion generated in the optical fiber strain sensor 13.

  Therefore, in the adjusting device 4 in the radiation measuring apparatus of the present embodiment, the strain amount of the scintillation fiber 1 is measured by the strain measuring device 12a, similarly to the adjusting device 4 of the radiation measuring apparatus of the embodiment shown in FIG. Based on the result, the noise cut threshold value of the discriminators 7a and 7b can be set.

  Therefore, the same effect as that of the embodiment of FIG. 1 can be obtained also by the radiation measuring apparatus of the present embodiment.

  By the way, when the scintillation fiber 1 is distorted, it may be considered that the scintillation light is attenuated as the scintillation light is attenuated.

  In view of this point, the radiation measuring apparatus I of the present invention may be configured to be able to add correction of the radiation count value as described below when measuring radiation.

  That is, the measurement system 2 includes a storage unit 14 as indicated by a two-dot chain line in FIGS.

  The radiation measuring apparatus I of the present invention having such a configuration uses a standard dose before starting actual measurement of radiation, and uses the standard dose for each of the plurality of required intervals in the longitudinal direction of the scintillation fiber 1. An operation simulating the case where the place is the radiation incident position is performed. At this time, the radiation count values of the scintillation fiber 1 in the longitudinal direction are measured by measuring the radiation count values based on the scintillation light incident on the photodetectors 5a and 5b at the one end and the other end of the scintillation fiber 1, respectively. The correlation with the counting down of the count value is obtained, and the obtained correlation is stored in the storage means 14.

  Thereafter, when the radiation measurement apparatus I of the present invention starts measurement of actual radiation, the time-wave height converter 8 detects the incident position of the radiation in the longitudinal direction of the scintillation fiber 1 as described above. become.

  As described above, when the time-wave height converter 8 detects the incident position of the radiation in the longitudinal direction of the scintillation fiber 1, the multichannel analyzer 10 stores the detection result of the incident position of the radiation in the storage unit 14. Based on the stored radiation incident position in the longitudinal direction of the scintillation fiber 1 and the correlation of counting off the count value of radiation, correction is made to compensate for the count-down of the count value, and then the corrected radiation The spatial distribution of the radiation dose with respect to the longitudinal direction of the scintillation fiber 1 is obtained on the basis of the counted values.

  In this way, even if the scintillation fiber 1 is distorted, the counting off of the radiation count value can be corrected. Therefore, the multi-channel analyzer 10 allows the radiation in the longitudinal direction of the scintillation fiber 1 to be corrected. The spatial distribution of quantities can be determined more accurately.

  In addition, this invention is not limited only to the said embodiment, You may set the length of the scintillation fiber 1 freely. The arrangement of the scintillation fiber 1 may be any arrangement other than the illustrated arc shape according to the radiation measurement target or the like.

  In the embodiment of FIG. 1, the number of attachments and the attachment interval of the strain gauges 11 in the longitudinal direction of the scintillation fiber 1 may be set freely. Further, the mounting interval of the strain gauges 11 in the longitudinal direction of the scintillation fiber 1 may not be constant. Furthermore, if the scintillation fiber 1 is partially fixed in a linear arrangement or the like, and there is a place where there is no possibility of distortion in the scintillation fiber 1, a strain gauge 11 is attached to the place. It does not have to be.

  In the embodiment of FIG. 2, a plurality of optical fiber strain sensors 13 may be attached in the longitudinal direction of the scintillation fiber 1 according to the longitudinal dimension of the scintillation fiber 1 or the like. In addition, when the scintillation fiber 1 is partially fixed in a linear arrangement or the like, and there is a place where there is no possibility of distortion in the scintillation fiber 1, an optical fiber strain sensor is provided at the place. 13 may not be attached.

  The measuring system 2 connected to the scintillation fiber 1 has a reflecting means on one end side of the scintillation fiber 1 and a photodetector on the other end side, instead of the configuration including the photodetectors 5a and 5b on both ends of the scintillation fiber 1. It is good also as an attached structure. The photodetector may have a configuration in which a time-wave height converter 8 similar to that shown in FIGS. 1 and 2 is connected via an amplifier and a discriminator. In this case, when the scintillation light generated by the incidence of radiation on the scintillation fiber 1 reaches one end side of the scintillation fiber 1, it is reflected by the reflecting means and then travels toward the other end side. For this reason, in the said light detection means, the detection of a scintillation light comes to be detected twice with the time difference according to the incident position of the said radiation with the incidence of one time of radiation. Therefore, based on this time difference, in the measurement system, the time-wave height converter 8 can detect the incident position of the radiation in the longitudinal direction of the scintillation fiber 1. It can be performed.

  Any strain sensor other than the strain gauge 11 and the optical fiber strain sensor 13 may be used as the strain sensor provided in the strain measuring means 3 and 3a as long as the strain amount of the scintillation fiber 1 can be measured.

  Of course, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS I Radiation measuring device 1 Scintillation fiber 2 Measuring system 3, 3a Strain measuring means 4 Adjustment device 5a, 5b Photodetector 6a, 6b Amplifier 7a, 7b Discriminator 8 Time-wave height converter 10 Multichannel analyzer 11 Strain gauge 13 Light Fiber strain sensor 14 Storage means

Claims (5)

Scintillation fiber,
Comprising a scintillation fiber measurement system;
The measurement system includes a photodetector connected to the scintillation fiber, an amplifier that amplifies the radiation detection signal output from the photodetector, and noise is removed from the detection signal amplified by the amplifier using a noise cut threshold. Discriminator, a time-wave height converter for detecting the incident position of the radiation in the longitudinal direction of the scintillation fiber based on a detection signal inputted through the discriminator, and radiation along the longitudinal direction of the scintillation fiber With a multi-channel analyzer that calculates the spatial distribution of quantities,
Furthermore, strain measuring means for detecting strain of the scintillation fiber,
Radiation comprising: an adjustment device that adjusts a noise cut threshold of a discriminator of the measurement system based on a measurement result of a strain amount of the scintillation fiber measured by the strain measurement means Measuring device.   The adjusting device includes a function for issuing an alarm when the noise cut threshold value of the discriminator is set and the set value of the noise cut threshold value is lower than a preset allowable level. The radiation measuring apparatus described. The measurement system is provided with a storage means, and the storage means is obtained by an operation simulating the case where a plurality of locations of the scintillation fiber in which distortion exists using a standard dose, where each location is an incident position of radiation. It is possible to memorize the correlation between the radiation incident position in the longitudinal direction of the scintillation fiber and the counting off of the radiation count value,
Further, the multi-channel analyzer correlates the detection result of the incident position of the radiation by the time-wave height converter and the counting of the radiation incident position in the longitudinal direction of the scintillation fiber stored in the storage means and the counted value of the radiation. Based on the above, a correction to compensate for the count-down of the count value is performed, and then a function for obtaining a spatial distribution of the radiation dose in the longitudinal direction of the scintillation fiber based on the corrected count value of the radiation is provided. The radiation measuring apparatus according to claim 1 or 2.   4. The radiation measuring apparatus according to claim 1, wherein the strain measuring means includes a strain gauge attached to the scintillation fiber.   4. The radiation measuring apparatus according to claim 1, wherein the strain measuring means includes an optical fiber strain sensor attached along the scintillation fiber.

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