JP2014215088A - Radiation detector, radiation detection method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector, a radiation detection method, and a computer program capable of detecting radiation with high sensitivity and accuracy.SOLUTION: A radiation detector 4 collects electrons generated by radiation inside a semiconductor block 13 by any of a plurality of anodes (first electrodes) 11, and counts a detection signal corresponding to a charge amount in a signal processing part 3. The electrons generated by radiation which is incident in the intermediate part among the plurality of anodes 11 are dispersed in the plurality of anodes 11 and then collected. When a peculiar signal which is the detection signal generated at this time is counted, the number of counts and energy of the radiation become obscure. The signal processing part 3 determines whether or not the detection signal is the peculiar signal based on temporal characteristics of the detection signal, and does not count the peculiar signal. As a result, detection accuracy can be increased without requiring a shield for reducing detection sensitivity.

Description

  The present invention relates to a radiation detector having a plurality of radiation detection electrodes, a radiation detection method, and a computer program for executing a part of the processing of the radiation detector.

  Some radiation detectors that detect radiation such as X-rays use semiconductor radiation detection elements. In the semiconductor radiation detection element, a first electrode for signal output and a second electrode for bias application are attached to a semiconductor such as silicon or germanium. When a bias voltage is applied, an electric field is generated between the first electrode and the second electrode inside the semiconductor radiation detection element. When radiation is incident on the semiconductor radiation detection element, the number of electron-hole pairs corresponding to the energy of the radiation is generated, and the electrons and holes move according to the electric field, and the electrons or holes move to the first electrode. The collected signals are output from the first electrode according to the amount of charge of electrons or holes.

  Some conventional semiconductor radiation detection elements include a plurality of first electrodes. For example, a semiconductor radiation detection element having a plurality of first electrodes arranged two-dimensionally on one surface of a plate-like semiconductor and a second electrode on the other surface is used. Patent Document 1 discloses an X-ray detector provided with a plurality of first electrodes in a semiconductor radiation detection element. When radiation is incident, electrons or holes are collected at the nearest first electrode, and a signal is output from the first electrode where the electrons or holes are collected. By dividing the first electrode into a plurality, the leakage current generated in the semiconductor is also divided, the influence of the leakage current included in the signal from each first electrode is reduced, and the S / N ratio of the signal is improved. In addition, when radiation is incident, since a certain amount of time is required for signal processing, a period during which radiation cannot be detected occurs. By providing a plurality of first electrodes, radiation can be detected using another first electrode even immediately after detecting radiation using one first electrode, so that the efficiency of detecting radiation is improved. . Also, since electrons or holes generated by radiation are collected at the nearest first electrode, the time required for electrons or holes to move is shorter than when there is only one first electrode, which is necessary for signal processing for radiation detection. Time is reduced.

Japanese Utility Model Publication No. 6-79162

  In a radiation detector in which a semiconductor radiation detection element includes a plurality of first electrodes, when radiation is incident between the plurality of first electrodes, the generated electrons or holes are dispersed and collected on the plurality of first electrodes. There is. At this time, signals are generated from a plurality of first electrodes for one radiation, and the count number and energy of the radiation are unknown. Although signals from a plurality of first electrodes can be added, noise included in the signal is generated for each first electrode. Therefore, noise included in the added signal is noise generated at the plurality of first electrodes. The signal is added, and the S / N ratio of the signal deteriorates. In order to solve these problems, it is conceivable to provide a shield so that radiation does not enter between the plurality of first electrodes. However, in order to ensure that no radiation is incident, it is necessary to make the shield somewhat large due to processing accuracy, and the area that can be used for radiation detection is reduced, and the radiation detection sensitivity is reduced. There's a problem. In addition, there is a problem that the cost increases by providing the shield.

  This invention is made | formed in view of such a situation, The place made into the objective is by preventing detecting one radiation using a some 1st electrode, without providing a shield. Another object of the present invention is to provide a radiation detector capable of detecting radiation with high sensitivity and accuracy, a radiation detection method, and a computer program for executing part of the processing of the radiation detector.

  A radiation detector according to the present invention is provided in a semiconductor, the semiconductor, a plurality of first electrodes that collect charges generated in the semiconductor by incidence of radiation, and provided in the semiconductor. A second electrode to which a bias voltage necessary for collection is applied, a signal output unit that outputs a signal corresponding to the charge collected by each first electrode, and a signal counting unit that counts the signal output by the signal output unit A determination unit that determines whether the signal is a singular signal having a predetermined characteristic based on a temporal characteristic of the signal output from the signal output unit, and the signal The counting unit is configured not to count the signal determined by the determination unit as a singular signal.

  In the radiation detector according to the present invention, the determination unit calculates a change rate of a signal value with respect to time of a signal output from the signal output unit, and the change rate calculated by the change rate calculation unit. And a singular signal determining unit that determines that the signal is a singular signal when the absolute value of is a predetermined value or less.

  In the radiation detector according to the present invention, the determination unit measures a time length of a signal output from the signal output unit, and the time length measured by the time measurement unit is a predetermined value or more. In some cases, the signal includes a singular signal determination unit that determines that the signal is a singular signal.

  In the radiation detector according to the present invention, the determination unit includes a time interval measurement unit that measures a time interval of a signal generated from two first electrodes as a starting point, and the time interval measured by the time interval measurement unit. And a singular signal determination unit that determines that the signal is a singular signal when the signal is equal to or less than a predetermined value.

  In the radiation detector according to the present invention, the determination unit measures a rate of change of the signal value with respect to time of the signal output from the signal output unit, or a time unit of the signal output from the signal output unit; A time interval measurement unit for measuring a time interval of signals generated from two first electrodes as a starting point, and an absolute value of the change rate measured by the measurement unit is equal to or less than a first predetermined value, or When the time length measured by the measurement unit is equal to or greater than a second predetermined value, and the time interval measured by the time interval measurement unit is equal to or less than a third predetermined value, the signal is a singular signal. And a singular signal determination unit that determines that the signal exists.

  The radiation detection method according to the present invention includes a semiconductor, a plurality of first electrodes that are provided on the semiconductor, collect charges generated in the semiconductor by incidence of radiation, and are provided on the semiconductor. A second electrode to which a bias voltage necessary for collection is applied, a signal output unit that outputs a signal corresponding to the charge collected by each first electrode, and a signal counting unit that counts the signal output by the signal output unit In a method of detecting radiation using a radiation detector comprising: whether or not the signal is a singular signal having a predetermined characteristic based on a temporal characteristic of the signal output by the signal output unit. A signal that is determined and determined to be a singular signal is not counted by the signal counting unit.

  A computer program according to the present invention is provided in a semiconductor, a plurality of first electrodes that are provided in the semiconductor and collects charges generated in the semiconductor by incidence of radiation, and is provided in the semiconductor and collects the charges. A second electrode to which a bias voltage necessary for the first electrode is applied, a signal output unit that outputs a signal corresponding to the charge collected by each first electrode, and a predetermined feature among the signals output by the signal output unit. A process of counting a signal that is not a specific signal and having a signal detector that does not count a specific signal and a calculation unit, and determining whether the signal output from the signal output unit is a specific signal A computer program for causing the arithmetic unit to execute the step of calculating the rate of change of the signal value with respect to the time of the signal output from the signal output unit to the arithmetic unit; If the absolute value of a more calculated the rate of change is less than the predetermined value, the signal is characterized in that to execute the processing including determining that a specific signal.

  In the present invention, a radiation detector that generates a detection signal by collecting charges generated in a semiconductor by radiation at any one of the plurality of first electrodes, has a specific characteristic when the detection signal is counted. Do not count signals. More specifically, the radiation detector does not count a signal having a characteristic that is generated when electric charges generated by the same radiation are dispersed to a plurality of first electrodes. Radiation is detected such that the number of counts and energy are unknown due to the charge being dispersed and collected by the plurality of first electrodes.

  In the present invention, the radiation detector determines that the detection signal is a singular signal when the rate of change of the signal value with respect to time of the detection signal is a predetermined value or less. The charge collected by the plurality of first electrodes takes a long time from generation to collection by the first electrode, and the rate of change of the signal rate becomes small. Therefore, the specific signal is based on the rate of change of the signal rate. Can be determined.

  In the present invention, the radiation detector determines that the detection signal is a singular signal when the time length of the detection signal is a predetermined value or more. The charge collected by the plurality of first electrodes takes a long time from generation to collection by the first electrode, and the rise time of the specific signal becomes long. Based on this, the singular signal can be determined.

  In the present invention, the radiation detector determines that the detection signal is a singular signal when the time interval between the two detection signals is a predetermined value or less. Since the charges generated by the same radiation are distributed and collected by the plurality of first electrodes, a plurality of detection signals are generated almost simultaneously, so that the singular signal is determined based on the time interval between the two detection signals. Is possible.

  In the present invention, the radiation detector is such that the rate of change of the signal value with respect to the time of the detection signal is equal to or less than the first predetermined value, or the time length of the detection signal is equal to or greater than the second predetermined value. And the condition that the time interval between the two detection signals is equal to or smaller than the third predetermined value is satisfied, it is determined that the detection signal is a singular signal.

  In the present invention, the radiation detector can prevent detection of radiation in which the count number and energy are unknown without using a shield. Therefore, the present invention has excellent effects such as that the radiation detector can detect radiation with high sensitivity and accuracy without increasing the cost.

It is a block diagram which shows the structure of a radiation detector. It is a typical top view which shows the example of the external appearance of a semiconductor radiation detection element. It is a schematic plan view which shows the other example of the external appearance of a semiconductor radiation detection element. It is a characteristic view which shows typically the electric potential distribution inside a semiconductor block. It is a characteristic view which shows the example of the detection signal which an amplifier outputs. 3 is a block diagram illustrating a functional configuration of a signal processing unit according to Embodiment 1. FIG. It is a characteristic view which shows the example of the detection signal which two amplification parts output. 10 is a block diagram illustrating a functional configuration of a signal processing unit according to Embodiment 3. FIG. FIG. 10 is a block diagram illustrating a functional configuration of a signal processing unit according to a fourth embodiment. FIG. 10 is a block diagram illustrating a functional configuration of a signal processing unit according to a fifth embodiment. It is a flowchart which shows the procedure of the process which CPU performs.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the radiation detector. The radiation detector 4 includes a semiconductor radiation detection element 1. In FIG. 1, the semiconductor radiation detection element 1 is shown in a partial cross-sectional view. The semiconductor radiation detection element 1 is configured by bonding a plurality of anodes (first electrodes) 11 to the surface of a plate-like semiconductor block 13 and bonding a cathode (second electrode) 12 to the back surface of the semiconductor block 13. . The semiconductor block 13 is formed of a semiconductor crystal such as silicon or germanium or a compound semiconductor such as cadmium / tellurium. FIG. 2 is a schematic plan view showing an example of the appearance of the semiconductor radiation detection element 1. As shown in FIG. 2, the plurality of anodes 11 are two-dimensionally arranged on the surface of the semiconductor block 13. The cathode 12 is disposed on the entire back surface of the semiconductor block 13. The semiconductor radiation detection element 1 is used so that radiation enters from the back side of the semiconductor block 13. A bias power source 21 is connected to the cathode 12, and a negative bias voltage is applied from the bias power source 21 compared to the ground potential. The bias power supply 21 may be configured to apply a bias voltage between the plurality of anodes 11 and the cathodes 12. Further, the radiation detector 4 may have a configuration including a cooling mechanism (not shown) for cooling the semiconductor radiation detection element 1 such as a cooler or a Peltier element using liquid nitrogen.

  The semiconductor radiation detection element 1 may have a form in which the cathode 12 is provided around the anode 11 on the surface of the semiconductor block 13 in addition to the cathode 12 arranged on the back surface of the semiconductor block 13. FIG. 3 is a schematic plan view showing another example of the appearance of the semiconductor radiation detection element 1. An annular cathode 12 is arranged around each anode 11. FIG. 3 shows an example in which the cathodes 12 surrounding the anodes 11 in a double manner are shown. However, the cathodes 12 may surround each anode 11 in a single layer, or may surround three or more layers. Good. As described above, the semiconductor radiation detection element 1 may be provided with a plurality of cathodes 12.

  By applying a bias voltage to the cathode 12, an electric field is generated in the semiconductor block 13 with the potentials of the plurality of anodes 11 being positive and the potential of the cathode 12 being negative. When radiation enters the semiconductor radiation detection element 1, a number of electron-hole pairs corresponding to the energy of the radiation are generated in the semiconductor block 13. Electrons in the generated electron-hole pairs are accelerated by the electric field in the semiconductor block 13 and collected by any one of the anodes 11 having a positive potential. Usually, electrons generated by radiation are collected at the anode 11 closest to the generated position in the semiconductor block 13. The anode 11 that has collected the electrons outputs a charge signal corresponding to the amount of charges of the collected electrons.

  An amplification unit 22 is connected to the anode 11. The amplifying unit 22 includes a preamplifier that converts a charge signal output from the anode 11 into a voltage signal, and a main amplifier that amplifies a signal from the preamplifier. The amplifying unit 22 outputs the amplified signal. Thus, the amplification unit 22 corresponds to a signal output unit that outputs a signal having an intensity corresponding to the amount of charge of electrons collected by the anode 11. Hereinafter, a signal output from the amplifying unit 22 is referred to as a detection signal. Note that the amplifying unit 22 may be configured to output a current signal.

  The signal processing unit 3 is connected to the amplification unit 22. The signal processing unit 3 counts the detection signal output from the amplification unit 22 for each signal intensity, and performs a process of generating a spectrum in which the radiation energy corresponding to the signal intensity is associated with the count number. The amplification unit 22 and the signal processing unit 3 are connected to each of the plurality of anodes 11. The amplification unit 22 and the signal processing unit 3 connected to each anode 11 operate independently of the amplification unit 22 and the signal processing unit 3 connected to the other anodes 11. The plurality of signal processing units 3 are connected to an information processing device 5 outside the radiation detector 4. The information processing device 5 is a computer such as a personal computer, and integrates the spectra generated by the signal processing units 3, generates the radiation spectrum by adding the integrated spectra, and outputs the spectrum as necessary. Execute.

  FIG. 4 is a characteristic diagram schematically showing the potential distribution inside the semiconductor block 13. The horizontal axis in the figure indicates the position, and the vertical axis indicates the negative potential. FIG. 4 shows a potential distribution between two points located directly below the centers of the two anodes 11. Further, the potential distribution in the semiconductor block 13 in the semiconductor radiation detection element 1 shown in FIG. 2 is indicated by a solid line, and the potential distribution in the semiconductor block 13 in the semiconductor radiation detection element 1 shown in FIG. 3 is indicated by a broken line. The closer to the center of each anode 11, the lower the negative potential (higher potential) and the farther from the center of any anode 11 between the two anodes 11, the higher the negative potential (lower potential). Yes. At a position close to the center of one anode 11, the negative potential decreases when moving toward the center of the nearest anode 11, and the negative potential increases when moving toward the center of another anode 11. For this reason, the electrons generated at this position move toward the center of the nearest anode 11 and are collected by the nearest anode 11. In the middle of the two anodes 11, the generated electrons can move to either anode 11 and be collected. Also, in the vicinity of the middle of the two anodes 11, even if the negative potential moves in a higher direction, the potential difference from the position where the negative potential is maximum is small (the electric field is small), so that the generated electrons overcome the potential difference. There is a possibility of moving toward the center of the distant anode 11. As described above, the semiconductor block 13 includes a main region in which the anode 11 from which electrons generated by radiation are collected is uniquely determined, and a boundary region in which the anode 11 from which electrons are collected is not uniquely determined. Exists. The main region corresponds to a portion directly below each anode 11, and the boundary region corresponds to a portion directly below the gap between the plurality of anodes 11.

  When radiation enters the semiconductor block 13 and electron-hole pairs are generated in the boundary region, the generated electrons may be dispersed and collected by the plurality of anodes 11. When electrons are dispersed in the two anodes 11, two detection signals are generated starting from the two anodes 11, the radiation count is doubled, and the radiation count is inaccurate. Moreover, the amount of electrons collected by one anode 11 is reduced due to the dispersion of the electrons, the signal intensity of the detection signal is lowered, and the energy of the radiation becomes inaccurate. In order to avoid these problems, the signal processing unit 3 according to the present embodiment, when counting the detection signal, has a specific signal having a predetermined characteristic due to electrons generated in the boundary region in the detection signal. Execute processing to prevent counting.

  FIG. 5 is a characteristic diagram illustrating an example of a detection signal output from the amplification unit 22. The amplifying unit 22 outputs a detection signal whose signal value rises in a stepped manner according to the amount of charge of electrons collected by the anode 11. The amount of electrons generated by the radiation and collected by the anode 11 corresponds to the energy of the radiation, and the amount of electrons corresponds to the amount of charge, so that the signal intensity rising in a step shape corresponds to the energy of the radiation. FIG. 5A shows a detection signal when electrons are generated in the main region of the semiconductor block 13, and FIG. 5B shows a singular signal due to electrons generated in the boundary region. In the figure, the horizontal axis represents time, and the vertical axis represents the signal value. In the boundary region, the electric field strength in the semiconductor block 13 is lower than that in the main region, and the physical distance to the anode 11 is long. Therefore, it takes a long time for the generated electrons to be collected by the anode 11. Therefore, as shown in FIG. 5, the signal value of the singular signal changes more slowly with respect to time than the detection signal caused by the electrons generated in the main region. The signal processing unit 3 performs processing for determining a singular signal based on the change rate of the signal value.

  FIG. 6 is a block diagram illustrating a functional configuration of the signal processing unit 3 according to the first embodiment. The signal processing unit 3 includes an A / D (analog / digital) conversion unit 31. The A / D conversion unit 31 is connected to the amplification unit 22, and receives the detection signal output from the amplification unit 22, and performs A / D conversion. A delay circuit 311 and a filter circuit 32 are connected to the A / D conversion unit 31, and the A / D conversion unit 31 inputs a detection signal after A / D conversion to the delay circuit 311 and the filter circuit 32. The filter circuit 32 performs Fast-type filter processing and Slow-type filter processing on the detection signal. The fast filter processing extracts a rapid time change of the detection signal, and generates a fast signal that indicates the rising start of the detection signal in a pulse shape. The slow filtering process extracts a gradual time change of the detection signal, and generates a slow signal having a high S / N ratio and a wave height corresponding to the signal strength of the detection signal. A pulse detection circuit 33 is connected to the filter circuit 32, and the filter circuit 32 inputs a Fast system signal and a Slow system signal to the pulse detection circuit 33.

  The pulse detection circuit 33 detects the rising start point of the detection signal from the Fast system signal. For example, the pulse detection circuit 33 stores a predetermined threshold value in advance, and detects a time point when the signal value of the Fast system signal is equal to or greater than the threshold value. A delay circuit 331 is connected to the pulse detection circuit 33, and the pulse detection circuit 33 inputs a signal indicating the rising start time of the detection signal to the delay circuit 331. Further, a P / H (peak / hold) circuit 34 is connected to the pulse detection circuit 33, and the pulse detection circuit 33 inputs a slow system signal to the P / H circuit 34.

  The P / H circuit 34 detects the signal strength of the detection signal from the Slow system signal. Specifically, the P / H circuit 34 detects the maximum value of the signal value of the Slow system signal. The maximum signal value of the slow signal corresponds to the signal intensity of the detection signal, and the signal intensity of the detection signal corresponds to the energy of the radiation. A delay circuit 341 is connected to the P / H circuit 34, and the P / H circuit 34 inputs a signal indicating the rising end point of the detection signal to the delay circuit 341. Also, delay circuits 342 and 343 are connected to the P / H circuit 34, and the P / H circuit 34 inputs a signal indicating the signal strength of the detection signal to the delay circuits 342 and 343.

  The signal processing unit 3 includes a time measuring unit 35 that measures the time length of the detection signal. The time measurement unit 35 is connected to the delay circuits 311, 331, and 341, receives a detection signal from the delay circuit 311, receives a signal indicating a rising start time of the detection signal from the delay circuit 331, and receives from the delay circuit 341. A signal indicating the rising end time of the detection signal is input. The delay circuits 311, 331, and 341 perform processing for adjusting the input timing so that the respective signals are input to the time measuring unit 35 in synchronization. The time measurement unit 35 sets the signal value to a value corresponding to the second predetermined ratio of the signal strength from the time when the signal value reaches the value corresponding to the first predetermined ratio of the signal strength as the time length of the detection signal. Measure the length of time elapsed until the point is reached. For example, the detection signal detects when the signal value reaches a value corresponding to 10% of the change amount of the signal from the rising start time to the rising end time and when the signal value reaches a value corresponding to 90%. And the length of elapsed time between the detected time points is calculated. Note that the time measuring unit 35 may perform a process of calculating the length of elapsed time from the rising start point to the rising end point.

  The signal processing unit 3 includes a determination processing unit 36 that executes processing for determining a singular signal. The determination processing unit 36 is connected to the time measuring unit 35 and the delay circuit 342, and receives a signal indicating the signal strength of the detection signal from the delay circuit 342. In addition, the time measuring unit 35 inputs a signal indicating the measured time length of the detection signal to the determination processing unit 36. The delay circuit 342 performs a process of adjusting the input timing so that a signal indicating the time length of the detection signal and a signal indicating the signal strength of the detection signal are input to the determination processing unit 36 in synchronization. The determination processing unit 36 measures the rate of change of the signal value with respect to time of the detection signal. For example, the rate of change of the signal value is calculated by dividing a value of 80% of the signal intensity of the detection signal by the time length of the detection signal measured by the time measurement unit 35. Next, the determination processing unit 36 determines whether or not the change rate of the measured signal value is equal to or less than a predetermined value. The predetermined value is stored in the determination processing unit 36 in advance. For example, the determination processing unit 36 represents the signal value as a voltage, and determines whether the change rate of the signal value is 1 mV / ns or less. As shown in FIG. 5, the singular signal has a slow change in signal value with respect to time, and the change rate of the signal value becomes small. For this reason, when the rate of change of the signal value is less than or equal to the reference value, it can be determined that the detection signal is a singular signal. Next, the determination processing unit 36 determines that the detection signal is a singular signal when the change rate of the signal value is equal to or less than a predetermined value, and the detection signal is the singular signal when the change rate of the signal value is larger than the predetermined value. It determines that it is not, and outputs the signal which shows the determination result.

  The signal processing unit 3 includes an MCA (multichannel analyzer) 37. The MCA 37 corresponds to a signal counting unit. The MCA 37 is connected to the determination processing unit 36 and the delay circuit 343. The MCA 37 receives a signal indicating the determination result of the detection signal from the determination processing unit 36, and receives a signal indicating the signal strength of the detection signal from the delay circuit 343. The The delay circuit 343 performs a process of adjusting the input timing so that the signal indicating the detection result of the detection signal and the signal indicating the signal strength of the detection signal are input to the determination processing unit 36 in synchronization. When receiving a signal indicating a determination result that the detection signal is not a singular signal, the MCA 37 counts the detection signal in association with the signal strength. Further, the MCA 37 does not perform counting associated with the signal strength when a signal indicating a determination result that the detection signal is a singular signal is input. As a result, the singular signal is not counted by the MCA 37, and detection of radiation that generates electrons in the boundary region of the semiconductor block 13 is prevented. In this way, the MCA 37 counts detection signals other than singular signals for each signal intensity, and generates a spectrum that associates the energy of radiation with the number of counts. The MCA 37 outputs data indicating the generated spectrum to the information processing device 5.

  In the present embodiment, the time measurement unit 35 and the determination processing unit 36 correspond to a determination unit. In addition, the time measurement unit 35 and a part of the processing of the determination processing unit 36 correspond to the change rate calculation unit, and the other part of the processing of the determination processing unit 36 corresponds to the singular signal determination unit. The signal processing unit 3 may include an independent change rate calculation unit that calculates the change rate of the signal value without using the time measurement unit 35 by a method such as differentiation of the signal value.

  As described in detail above, in the present embodiment, when the radiation detector 4 counts detection signals according to the incidence of radiation, electrons generated by the same radiation are collected by the plurality of anodes 11. Do not count singular signals having characteristics due to. The radiation detector 4 determines that the detection signal is a singular signal when the rate of change of the signal value with respect to time of the detection signal is equal to or less than a predetermined value. Since electrons collected by the plurality of anodes 11 take a long time from generation to collection by the anode 11, the change rate of the signal rate becomes small. Therefore, the singular signal can be determined based on the rate of change of the signal rate. By not counting the singular signal, it is possible to detect the radiation such that electrons generated in the boundary region of the semiconductor block 13 are collected by the plurality of anodes 11 and prevent the radiation count number and energy from becoming inaccurate. be able to. On the other hand, the radiation detector 4 can accurately obtain the count number and energy for the radiation that generates electrons in the main region of the semiconductor block 13. In addition, since the anode 11, the amplification unit 22, and the signal processing unit 3 used to detect one radiation are limited to one, the amount of noise is limited, and deterioration of the signal S / N ratio is prevented. The Further, since it is not necessary to use a shield for preventing radiation from entering the boundary region, it is possible to prevent a decrease in radiation detection sensitivity and an increase in cost caused by the shield. Therefore, the radiation detector 4 can detect radiation with high sensitivity and accuracy without increasing costs.

(Embodiment 2)
In the second embodiment, a specific signal is determined based on the time length of the detection signal. As described in the first embodiment, it takes a long time for the electrons generated in the boundary region in the semiconductor block 13 to be collected by the anode 11. For this reason, as shown in FIG. 5, the singular signal has a longer rise time than the detection signal caused by electrons generated in the main region. Therefore, it is possible to determine a singular signal based on the time length of the detection signal.

  The configuration of the radiation detector 4 according to the present exemplary embodiment is the same as that of the first exemplary embodiment illustrated in FIG. The functional configuration of the signal processing unit 3 according to the present invention is the same as that of the second embodiment shown in FIG. The determination processing unit 36 stores in advance a predetermined reference value of the time length of the detection signal for determining the singular signal in association with the signal strength of the detection signal. When the energy of radiation is high, the signal intensity of the detection signal is also high, and the rise time length is also long. Therefore, the determination processing unit 36 stores in advance a time length reference value corresponding to each of a plurality of signal intensities. The determination processing unit 36 may store a time length reference value in association with the radiation energy. Further, the determination processing unit 36 may store a reference value common to all signal intensities.

  The A / D conversion unit 31, the filter circuit 32, the pulse detection circuit 33, the P / H circuit 34, the delay circuits 311, 331, 341, 342 and 343, and the time measurement unit 35 operate in the same manner as in the first embodiment. . The determination processing unit compares the time length of the detection signal measured by the time measurement unit with the reference value of the time length stored in association with the signal intensity indicated by the signal from the delay circuit 342, and detects the detection signal. It is determined whether or not the length of time is equal to or greater than a reference value. For example, the determination processing unit 36 determines whether or not the time length of the detection signal is 100 ns or more. As shown in FIG. 5, when the time length of the detection signal is longer than a certain level, it can be determined that the detection signal is a singular signal. Next, the determination processing unit 36 determines that the detection signal is a singular signal when the time length of the detection signal is equal to or greater than the reference value, and the detection signal is determined when the time length of the detection signal is shorter than the reference value. It is determined that the signal is not a unique signal, and a signal indicating the determination result is input to the MCA 37. The MCA 37 operates in the same manner as in the first embodiment. In the present embodiment, the determination processing unit 36 corresponds to a singular signal determination unit.

  As described above in detail, also in the present embodiment, the radiation detector 4 collects electrons generated by the same radiation at the plurality of anodes 11 when counting detection signals according to the incidence of radiation. Do not count singular signals having characteristics due to. The radiation detector 4 determines that the detection signal is a singular signal when the time length of the detection signal is equal to or greater than a predetermined reference value. Since electrons collected by the plurality of anodes 11 take a long time from generation to collection by the anode 11, the time length of rise of the specific signal becomes long. Therefore, the singular signal can be determined based on the time length of the detection signal. Also in the present embodiment, as in the first embodiment, the radiation detector 4 can detect radiation with high sensitivity and accuracy without increasing costs.

(Embodiment 3)
In the third embodiment, a specific signal is determined based on the time interval between two detection signals. FIG. 7 is a characteristic diagram illustrating an example of detection signals output from the two amplifying units 22. In the figure, the horizontal axis represents time, and the vertical axis represents the signal value. In FIG. 7, the detection signals output from the amplification units 22 connected to the two anodes 11 are compared on the same time axis. FIG. 7A shows a detection signal when electrons are generated in one main region of the semiconductor block 13 by the incidence of radiation and electrons are generated in another main region by another radiation. FIG. 7B shows a detection signal when electrons generated in the boundary region due to the incidence of radiation are collected by the two anodes 11. When electrons are generated in the main region, the rise time of the detection signal is short, and the probability that two detection signals are generated simultaneously is low. When electrons generated in the boundary region are distributed and collected by the two anodes 11, the electrons are collected by the two anodes 11 almost simultaneously, and two singular signals are generated almost simultaneously. Therefore, it is possible to determine the singular signal based on the time interval of generation of the detection signal output from the two amplifying units 22.

  The configuration of the radiation detector 4 according to the present exemplary embodiment is the same as that of the first exemplary embodiment illustrated in FIG. FIG. 8 is a block diagram illustrating a functional configuration of the signal processing unit 3 according to the third embodiment. The A / D conversion unit 31 A / D converts the detection signal output from the amplification unit 22 and inputs the detection signal after the A / D conversion to the filter circuit 32. The filter circuit 32 operates in the same manner as in the first embodiment. The pulse detection circuit 33 detects the rising start time of the detection signal from the Fast system signal, and inputs a signal indicating the rising start time to the delay circuit 332. Further, the pulse detection circuit 33 inputs a Slow system signal to the P / H circuit 34. Further, the pulse detection circuit 33 outputs a signal indicating the rising start point of the detection signal to the other signal processing unit 3. The P / H circuit 34 detects the signal strength of the detection signal from the Slow system signal, and inputs a signal indicating the signal strength to the delay circuit 343. Delay circuit 343 operates in the same manner as in the first embodiment.

  The signal processing unit 3 includes a time interval measuring unit 38 that measures a time interval between two detection signals. The time interval measuring unit 38 is connected to the delay circuit 332 and receives a signal indicating the rising start time of the detection signal from the delay circuit 332. Further, the time interval measurement unit 38 receives a signal indicating the rising start time of another detection signal output from the pulse detection circuit 33 of the other signal processing unit 3. The other signal is a detection signal output from another amplification unit 22 connected to another anode 11. The delay circuit 332 performs a process of adjusting the input timing so that the two signals are input to the time interval measurement unit 38 in synchronization. The time interval measurement unit 38 measures the time interval at which the two detection signals are generated by calculating the difference between the rising start points of the two detection signals. The time interval measurement unit 38 is connected to the determination processing unit 36 and inputs a signal indicating the time interval between the two detection signals to the determination processing unit 36.

  The determination processing unit 36 determines whether or not the time interval between the two detection signals measured by the time interval measuring unit 38 is equal to or less than a predetermined value. The predetermined value is stored in the determination processing unit 36 in advance. For example, the determination processing unit 36 determines whether the time interval is 50 ns or less. As shown in FIG. 7, the two singular signals generated when the electrons generated in the boundary region by the same radiation are collected by the two anodes 11 are generated almost simultaneously. Therefore, if the time interval between the two detection signals is considered to be simultaneous, such as when the time interval between the two detection signals is shorter than the rise time of the detection signal, the two detection signals can be determined to be singular signals. . Next, the determination processing unit 36 determines that the detection signal is a singular signal when the time interval is equal to or less than a predetermined value, and determines that the detection signal is not a singular signal when the time interval is greater than the predetermined value. A signal indicating the determination result is input to the MCA 37. The MCA 37 operates in the same manner as in the first embodiment. In the present embodiment, the determination processing unit 36 corresponds to a singular signal determination unit.

  As described in detail above, in the present embodiment, when the radiation detector 4 counts detection signals according to the incidence of radiation, electrons generated by the same radiation are collected by the plurality of anodes 11. Do not count singular signals having characteristics due to. The radiation detector 4 determines that the detection signal is a singular signal when the time interval between the two detection signals is equal to or less than a predetermined value. Also in the present embodiment, as in the first and second embodiments, the radiation detector 4 can detect radiation with high sensitivity and accuracy without increasing costs.

(Embodiment 4)
The configuration of the radiation detector 4 according to the fourth embodiment is the same as that of the first embodiment shown in FIG. FIG. 9 is a block diagram illustrating a functional configuration of the signal processing unit 3 according to the fourth embodiment. The signal processing unit 3 includes a time measurement unit 35 and a time interval measurement unit 38, and the time measurement unit 35 and the time interval measurement unit 38 are connected to the determination processing unit 36. The A / D converter 31 and the filter circuit 32 operate in the same manner as in the first embodiment. The pulse detection circuit 33 detects the rising start time of the detection signal and inputs a signal indicating the rising start time to the delay circuits 331 and 332. Further, the pulse detection circuit 33 inputs a Slow system signal to the P / H circuit 34. Further, the pulse detection circuit 33 outputs a signal indicating the rising start point of the detection signal to the other signal processing unit 3. The P / H circuit 34 operates in the same manner as in the first embodiment. The delay circuits 311, 331, 341, 342 and 343 and the time measuring unit 35 operate in the same manner as in the first embodiment. Further, the delay circuit 332 and the time interval measurement unit 38 operate in the same manner as in the third embodiment.

  The determination processing unit 36 uses the time length of the detection signal measured by the time measurement unit 35 to measure the rate of change of the signal value with respect to the time of the detection signal, as in the first embodiment. Next, the determination processing unit 36 determines whether or not the measured change rate of the signal value is equal to or less than a predetermined value (first predetermined value). Next, the determination processing unit 36 determines whether or not the time interval between the two detection signals measured by the time interval measuring unit 38 is equal to or less than another predetermined value (third predetermined value). Next, when the rate of change in the signal value of the detection signal is equal to or smaller than a predetermined value and the time interval between the two detection signals is equal to or smaller than the other predetermined value, the determination processing unit 36 determines that the detection signal is a singular signal. In other cases, it is determined that the detection signal is not a singular signal, and a signal indicating the determination result is input to the MCA 37. The MCA 37 operates in the same manner as in the first embodiment.

  The determination processing unit 36 may be configured to perform determination based on the time length of the detection signal. In this embodiment, the determination processing unit 36 associates and stores the time length of the detection signal measured by the time measuring unit 35 and the signal length indicated by the signal from the delay circuit 342 (second value). To determine whether the time length of the detection signal is equal to or greater than a reference value. Next, the determination processing unit 36 determines whether or not the time interval between the two detection signals measured by the time interval measuring unit 38 is equal to or less than a predetermined value (third predetermined value). Next, the determination processing unit 36 determines that the detection signal is a singular signal when the time length of the detection signal is equal to or greater than a reference value and the time interval between the two detection signals is equal to or less than a predetermined value. In other cases, it is determined that the detection signal is not a singular signal, and a signal indicating the determination result is input to the MCA 37. The MCA 37 operates in the same manner as in the first embodiment.

  Further, the determination processing unit 36 may be configured to perform determination using both the change rate of the signal value and the time length of the detection signal. In this embodiment, the determination processing unit 36 uses the time length of the detection signal measured by the time measurement unit 35 to measure the change rate of the signal value with respect to the time of the detection signal, and the change rate of the measured signal value is predetermined. It is determined whether or not it is equal to or less than a value (first predetermined value). The determination processing unit 36 further includes a reference value (second predetermined value) of the time length stored in association with the time length of the detection signal measured by the time measuring unit 35 and the signal intensity indicated by the signal from the delay circuit 342. Value) to determine whether or not the time length of the detection signal is greater than or equal to the reference value. Next, the determination processing unit 36 determines whether or not the time interval between the two detection signals measured by the time interval measuring unit 38 is equal to or less than a predetermined value (third predetermined value). Next, the determination processing unit 36 determines whether at least one of the change rate of the signal value of the detection signal is equal to or less than a predetermined value and that the time length of the detection signal is equal to or greater than a reference value. When the time interval between two detection signals is equal to or smaller than a predetermined value, the detection signal is determined to be a singular signal, and in other cases, the detection signal is determined not to be a singular signal. The determination processing unit 36 inputs a signal indicating the determination result to the MCA 37, and the MCA 37 operates in the same manner as in the first embodiment. In the fourth embodiment, the time measurement unit 35 and a part of the processing of the determination processing unit 36 correspond to the measurement unit.

  As described above in detail, in the present embodiment, the radiation detector 4 has a rate of change of the signal value with respect to the time of the detection signal being a predetermined value or less, or the time length of the detection signal is not less than a predetermined reference value. In addition, when the time interval between the two detection signals is equal to or less than another predetermined value, it is determined that the detection signal is a singular signal. Thereby, the radiation detector 4 can prohibit the count of a specific signal reliably. Even if a detection signal has a small change rate of a signal value or a detection signal having a long time length, electrons generated by the same radiation are collected by a plurality of anodes 11 as long as the time interval between the two detection signals is long. Since this phenomenon does not occur, the radiation count and energy can be accurately obtained without eliminating the detection signal as a singular signal. Even if the time interval between the two detection signals is short, if the rate of change of the signal value is large or the time length of the detection signal is short, electrons generated by the same radiation are collected by the plurality of anodes 11. Since this phenomenon does not occur, the radiation count and energy can be accurately obtained without eliminating the detection signal as a singular signal. Therefore, in the present embodiment, the radiation detector 4 can detect radiation with higher sensitivity and accuracy.

(Embodiment 5)
In the fifth embodiment, a form in which part of the processing is realized by software is shown. The configuration of the radiation detector 4 according to the fifth embodiment is the same as that of the first embodiment shown in FIG. FIG. 10 is a block diagram illustrating a functional configuration of the signal processing unit 3 according to the fifth embodiment. The signal processing unit 3 includes a CPU (Central Processing Unit) 61 that performs calculations, a RAM (Random Access Memory) 62 that stores temporary data generated along with the calculations, and a non-volatile storage unit 63 such as a flash memory. And. The CPU 61 corresponds to a calculation unit. The storage unit 63 stores a computer program 64. The CPU 61 is connected to the delay circuits 311, 331, 341 and 342 and the MCA 37.

  FIG. 11 is a flowchart showing a procedure of processing executed by the CPU 61. The CPU 61 executes the following processing according to the computer program 64. The A / D conversion unit 31, the filter circuit 32, the pulse detection circuit 33, the P / H circuit 34, and the delay circuit 343 operate in the same manner as in the first embodiment. The CPU 61 receives a detection signal from the delay circuit 311, receives a signal indicating the rising start time of the detection signal from the delay circuit 331, and receives a signal indicating the rising end time of the detection signal from the delay circuit 341, and the delay circuit 342. The signal indicating the signal strength of the detection signal is input (S1). Next, the CPU 61 calculates the time length of the detection signal in the same manner as the time measurement unit 35 (S2), and calculates the rate of change of the signal value with respect to the time of the detection signal using the calculated time length. (S3). Next, the CPU 61 determines whether or not the calculated change rate of the signal value is equal to or less than a predetermined value (S4). The predetermined value is included in the computer program 64 in advance or stored in the storage unit 63. When the change rate of the signal value of the detection signal is equal to or less than the predetermined value (S4: YES), the CPU 61 determines that the detection signal is a singular signal (S5). When the change rate of the signal value of the detection signal is larger than the predetermined value (S4: NO), the CPU 61 determines that the detection signal is not a singular signal (S6). After step S5 or S6 ends, the CPU 61 outputs a signal indicating the determination result to the MCA 37 (S7) and ends the process. The MCA 37 receives a signal indicating the determination result from the CPU 61 and operates in the same manner as in the first embodiment. As described above, also in the present embodiment, the radiation detector 4 collects electrons generated by the same radiation at the plurality of anodes 11 when counting detection signals according to the incidence of radiation. Do not count singular signals with the resulting characteristics.

  As in the second embodiment, the computer program 64 is configured to cause the CPU 61 to execute processing for determining that the detection signal is a singular signal when the time length of the detection signal is equal to or greater than a predetermined reference value. May be. Similarly to the third embodiment, the computer program 64 causes the CPU 61 to execute processing for determining that the detection signal is a singular signal when the time interval between the two detection signals is equal to or less than a predetermined value. Also good. Similarly to the fourth embodiment, the computer program 64 has a change rate of the signal value of the detection signal equal to or smaller than a predetermined value, or the time length of the detection signal is equal to or larger than a predetermined reference value. When the time interval between two detection signals is equal to or less than another predetermined value, the CPU 61 may be configured to execute a process of determining that the detection signal is a singular signal. Also in the present embodiment, the radiation detector 4 can detect radiation with high sensitivity and accuracy.

  In the first to fifth embodiments, an n-type semiconductor is used for the semiconductor block 13. The radiation detector 4 may have a form using a p-type semiconductor for the semiconductor block 13. In this embodiment, the radiation detector 4 includes the semiconductor block 13 made of a p-type semiconductor, the arrangement of the anode and the cathode is opposite to that of the first to fifth embodiments, the first electrode is the cathode, and the second electrode Is the anode. The radiation detector 4 applies a bias voltage so that the potential of the second electrode becomes positive, and collects holes generated by radiation at each of the plurality of first electrodes that are cathodes. The radiation detector 4 performs the same signal processing as in the first to fifth embodiments in the amplification unit 22 and the signal processing unit 3 except that electrons are replaced with holes. Also in this embodiment, the radiation detector 4 can detect the radiation with high sensitivity and accuracy without counting the singular signal.

  In the first to fifth embodiments, the detection signal is a signal that rises in a staircase pattern, but the radiation detector 4 may be a signal in which the detection signal is a falling signal or a pulse signal. Good. In the first to fifth embodiments, the detection signal output from the amplification unit 22 is A / D converted by the A / D conversion unit 31. However, the radiation detector 4 performs A / D conversion at other timings. The form which performs D conversion may be sufficient. For example, the radiation detector 4 may be configured to perform A / D conversion in the amplification unit 22, or may be configured to perform A / D conversion after the filter circuit 32. Moreover, in Embodiment 1-5, although the form which provided the signal processing part 3 separately about each anode 11 was shown, the radiation detector 4 has some in the signal processing parts 3, such as MCA37, severally. It may be configured in common with the anode 11.

DESCRIPTION OF SYMBOLS 1 Semiconductor radiation detection element 11 Anode (1st electrode)
12 Cathode (second electrode)
13 Semiconductor Block 21 Bias Power Supply 22 Amplification Unit (Signal Output Unit)
3 Signal Processing Unit 35 Time Measurement Unit 36 Judgment Processing Unit 37 MCA (Signal Counting Unit)
38 Time interval measurement unit 4 Radiation detector 61 CPU (calculation unit)
63 storage unit 64 computer program

Claims (7)

A semiconductor, a plurality of first electrodes provided on the semiconductor and collecting charges generated in the semiconductor upon incidence of radiation, and a bias voltage provided on the semiconductor and necessary for collecting the charge are applied. A radiation detector comprising: a second electrode; a signal output unit that outputs a signal corresponding to the charge collected by each first electrode; and a signal counting unit that counts a signal output from the signal output unit.
A determination unit that determines whether the signal is a singular signal having a predetermined characteristic based on a temporal characteristic of the signal output by the signal output unit;
The signal counter is
The radiation detector is configured not to count the signal determined by the determination unit as a singular signal. The determination unit
A rate of change calculation unit for calculating a rate of change of the signal value with respect to time of the signal output by the signal output unit;
2. The singular signal determination unit that determines that the signal is a singular signal when the absolute value of the variation rate calculated by the change rate calculation unit is equal to or less than a predetermined value. Radiation detector. The determination unit
A time measuring unit for measuring the time length of the signal output by the signal output unit;
The radiation detection according to claim 1, further comprising: a singular signal determination unit that determines that the signal is a singular signal when the time length measured by the time measurement unit is a predetermined value or more. vessel. The determination unit
A time interval measuring unit for measuring a time interval of a signal generated from two first electrodes as a starting point;
The radiation detection according to claim 1, further comprising: a singular signal determination unit that determines that the signal is a singular signal when the time interval measured by the time interval measurement unit is equal to or less than a predetermined value. vessel. The determination unit
A measurement unit that measures a rate of change of a signal value with respect to time of a signal output by the signal output unit, or a time length of a signal output by the signal output unit;
A time interval measuring unit for measuring a time interval of a signal generated from two first electrodes as a starting point;
The absolute value of the change rate measured by the measurement unit is less than or equal to a first predetermined value, or the time length measured by the measurement unit is greater than or equal to a second predetermined value, and the time interval measurement The radiation detector according to claim 1, further comprising: a singular signal determination unit that determines that the signal is a singular signal when the time interval measured by the unit is equal to or less than a third predetermined value. . A semiconductor, a plurality of first electrodes provided on the semiconductor and collecting charges generated in the semiconductor upon incidence of radiation, and a bias voltage provided on the semiconductor and necessary for collecting the charge are applied. A radiation detector including a second electrode, a signal output unit that outputs a signal corresponding to the charge collected by each first electrode, and a signal counter that counts a signal output from the signal output unit. In the method of detecting radiation,
Based on the temporal characteristics of the signal output by the signal output unit, determine whether the signal is a singular signal having a predetermined characteristic,
A radiation detection method, wherein a signal determined to be a singular signal is not counted by the signal counting unit. A semiconductor, a plurality of first electrodes provided on the semiconductor and collecting charges generated in the semiconductor upon incidence of radiation, and a bias voltage provided on the semiconductor and necessary for collecting the charge are applied. The second electrode, a signal output unit that outputs a signal corresponding to the charge collected by each first electrode, and a signal that is not a singular signal having a predetermined characteristic among the signals output by the signal output unit A computer that causes the arithmetic unit to execute a process of determining whether or not the signal output from the signal output unit is a singular signal in a radiation detector that includes a signal counting unit that does not count a singular signal and an arithmetic unit. A program,
In the calculation unit,
Calculating a change rate of a signal value with respect to time of a signal output by the signal output unit;
And a step of determining that the signal is a singular signal when the absolute value of the rate of change calculated in the step is equal to or less than a predetermined value.

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