JP2018179744A - Radiation detection apparatus, radiation detection method and radiation detection program - Google Patents

Abstract

A radiation detection apparatus, a radiation detection method, and a radiation detection program capable of obtaining high energy resolution with a simple configuration are provided. A radiation detection apparatus according to an embodiment of the present invention is a position indicating a position where the charge is generated, extracted from an output signal output based on a charge generated according to the energy of radiation incident on a semiconductor. Correction means for correcting the peak value of the waveform of the output signal using related information; and energy calculating means for obtaining energy of the radiation incident on the semiconductor using the peak value corrected by the correction means; Prepare. [Selection] Figure 1

Description

  Embodiments of the present invention relate to a radiation detection apparatus, a radiation detection method, and a radiation detection program.

  As a radiation detection device for detecting radiation such as gamma rays, beta rays, α rays, and X rays, a radiation detection device using a Ge semiconductor or a Si semiconductor as a radiation detection element is known. Since Ge and Si have small band gaps, many electron-hole pairs are generated when irradiated with radiation. Therefore, a radiation detection apparatus using Ge semiconductor or Si semiconductor for the detection element has higher energy resolution than a radiation detection apparatus using a scintillator for the detection element.

  However, since Ge semiconductors and Si semiconductors have small band gaps and are easily affected by thermal noise, they need to be cooled when detecting radiation. Therefore, conventionally, a radiation detection apparatus using a detection element which is resistant to thermal noise and usable at room temperature has been developed. As a detection element of this type, a compound semiconductor composed of two or more elements can be used.

  Compound semiconductors include II-IV semiconductors, III-V semiconductors, etc. For example, CdTe, HgI2, TlBr, etc. can be used as this kind of detection element. Compound semiconductors have a larger band gap and are less affected by thermal noise than Ge, Si, and the like. For this reason, it can be used at room temperature at the time of detection without requiring a large-scale cooling device used in a radiation detection device using Ge or Si.

JP, 2005-265859, A

  However, a compound semiconductor has a band gap larger than that of Ge, Si, and the like, mobility of electrons and holes is small, and carrier life is short because it is easily trapped in a crystal. For this reason, the radiation detection device using the compound semiconductor has poorer energy resolution than the radiation detection device using Ge or Si.

  As a method of improving the energy resolution of a compound semiconductor, there is known a method of correcting the magnitude of a signal by using a pixel electrode and estimating a detection position from the output signal intensity of a detection element. However, in this method, the number of circuits for extracting signals from the electrodes is significantly increased, and the configuration of the apparatus becomes complicated. Further, as another method for improving the energy resolution of a compound semiconductor, there is known a method in which the resistance value of the element is increased by cooling the detection element to increase the applied withstand voltage. However, this method requires a cooling device and a dehumidifier, which also makes the configuration very complicated.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a radiation detection apparatus, a radiation detection method, and a radiation detection program capable of obtaining high energy resolution with a simple configuration.

  In order to solve the problems described above, a radiation detection apparatus according to an embodiment of the present invention extracts the output signal output based on the charge generated according to the energy of the radiation incident on the semiconductor. A correction unit that corrects the crest value of the waveform using position related information indicating a generation position; and an energy calculation unit that calculates the energy of the incident radiation using the crest value corrected by the correction unit It is a thing.

Further, in the radiation detection method according to one embodiment of the present invention, in order to solve the problems described above, the electric charge is generated from the waveform of the signal output based on the electric charge generated according to the energy of the radiation incident on the semiconductor. Extracting position related information indicating a generation position of the wave, correcting a peak value of the waveform using the position related information, energy of the radiation incident on the semiconductor using the corrected peak value And a step of determining.
Furthermore, the radiation detection program according to one embodiment of the present invention is a computer program that indicates the generation position of the charge from the waveform of the signal output based on the charge generated according to the energy of the radiation incident on the semiconductor. Performing the steps of extracting related information, correcting the peak value of the waveform using the position related information, and determining the energy of the radiation incident on the semiconductor using the corrected peak value It is to make

  According to a radiation detection apparatus, a radiation detection method, and a radiation detection program according to an embodiment of the present invention, high energy resolution can be obtained with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows one structural example of the radiation detection apparatus which concerns on 1st Embodiment of this invention. Explanatory drawing which shows an example of a mode that the time (rise time) T0 which the output signal of the radiation detection means generate | occur | produced is acquired. Explanatory drawing which shows an example of the relationship between the generation | occurrence | production position of an electric charge, and a wave height value. Explanatory drawing which shows an example of the relationship between wave height value Vmax and peak time Tmax-T0. (A) is an explanatory drawing showing an example of how to extract peak time Tmax-T0 as position related information from the waveform of the output signal of the radiation detection means, (b) is a predetermined output signal as position related information from the waveform of the output signal Explanatory drawing which shows an example of a mode that T2-T1 during time to give the value V1 is extracted. FIG. 7 is a flow chart showing an example of a procedure for correcting the peak value Vmax of the waveform by the main control unit shown in FIG. 1 using the position related information extracted from the waveform of the output signal of the radiation detection unit. (A) is an explanatory view showing an example of the relationship between the output signal waveform of the radiation detection means and the electron contribution period Te, (b) is a diagram for explaining the relationship between the charge generation position Z and the moving distance d-Z of electrons Figure. The block diagram which shows an example of the radiation detection apparatus which concerns on 3rd Embodiment of this invention. The block diagram which shows an example of the radiation detection apparatus which concerns on 4th Embodiment of this invention. The block diagram which shows an example of the radiation detection apparatus which concerns on 5th Embodiment of this invention.

  Embodiments of a radiation detection apparatus, a radiation detection method, and a radiation detection program according to the present invention will be described with reference to the attached drawings.

First Embodiment
FIG. 1 is a block diagram showing a configuration example of a radiation detection apparatus 10 according to a first embodiment of the present invention.

  The radiation detection apparatus 10 includes, as shown in FIG. 1, a radiation detection means 11, a signal generation time acquisition means 12, a waveform acquisition means 13, and an information processing device 14.

  The radiation detection means 11 has a detection element 21, a high voltage power supply 22 and a charge amplifier 23. The detection element 21 has a semiconductor 24, an anode 25 and a cathode 26.

  The semiconductor 24 of the detection element 21 generates a charge according to the energy of the incident radiation. The radiation detection unit 11 outputs a signal corresponding to the charge generated by the semiconductor 24 to the signal generation time acquisition unit 12 and the waveform acquisition unit 13.

  As the semiconductor 24 of the detection element 21, for example, a compound semiconductor such as a II-IV group semiconductor or a III-V group semiconductor can be used in addition to a Ge semiconductor and a Si semiconductor. As a compound semiconductor used for semiconductor 24, CdTe, HgI2, TlBr etc. are mentioned, for example. When a compound semiconductor is used as the semiconductor 24, the radiation detection means 11 is more resistant to thermal noise than when using a Ge semiconductor or a Si semiconductor. In the following description, an example in the case of using a compound semiconductor such as CdTe or TlBr as the semiconductor 24 will be described.

  The anode 25 and the cathode 26 can be arbitrarily selected according to the material and shape of the semiconductor 24. For example, the anode 25 and the cathode 26 may be ohmic electrodes or Schottky electrodes. Further, the anode 25 and the cathode 26 may be pixel electrodes or Frisch grid electrodes.

  The high voltage power supply 22 is a voltage source that applies a voltage to the semiconductor 24 via the anode 25 and the cathode 26 in order to form an electric field in the semiconductor 24 of the detection element 21. The voltage applied by the high voltage power supply 22 may be determined according to the type, thickness, shape, and the like of the semiconductor 24.

  The high voltage power supply 22 may have a current limiting function. When the high voltage power supply 22 has a current limiting function, the current can be limited when a leak current occurs in the semiconductor 24, for example, when a high voltage is applied to the semiconductor 24 too much.

  The charge amplifier 23 is a discrete amplifier composed of an operational amplifier, a transistor, and the like. As charge amplifier 23, for example, a charge sensitive preamplifier or a current amplification preamplifier can be used.

  The charge amplifier 23 amplifies the output signal of the semiconductor 24 and supplies the amplified signal to the signal generation time acquisition means 12 and the waveform acquisition means 13. Specifically, the charge amplifier 23 converts the minute charge generated in the semiconductor 24 into a voltage with a predetermined conversion constant. The conversion constant may be set to a value that allows the signal generation time acquisition means 12 to correspond to the rising speed of the waveform of the output signal of the semiconductor 24. The charge amplifier 23 may have a circuit that integrates and differentiates the charge, and integrates the charge of the input pulse, for example, converts it into a pulse having a pulse wave height corresponding to the amount of the charge, and outputs it.

  As described above, the radiation detection unit 11 outputs a signal corresponding to the charge generated by the semiconductor 24, and supplies the output signal to the signal generation time acquisition unit 12 and the waveform acquisition unit 13.

  The type of radiation (eg, gamma rays, beta rays, alpha rays, etc.) detected by the semiconductor 24 is not particularly limited. Although FIG. 1 shows an example in which the coupling capacitor is provided at the front stage of the charge amplifier 23, when the leak current of the detection element 21 is small, the coupling capacitor may be omitted and DC coupling may be performed.

  FIG. 2 is an explanatory drawing showing an example of how the time (rise time) T0 at which the output signal of the radiation detection means 11 is generated is acquired. The upper part of FIG. 2 shows an example of the waveform of the output signal of the radiation detection means 11. The lower part of FIG. 2 shows an example of a signal indicating the rise time T0, which is output from the signal generation time acquiring means 12 to which the output signal having the waveform shown in the upper part of FIG. 2 is input.

  The signal generation time acquiring unit 12 is a device for acquiring a time T0 (hereinafter referred to as a rising time) at which an output signal of the radiation detecting unit 11 is generated according to the charge generated by the radiation incident on the semiconductor 24. Various circuits can be used as the signal generation time acquisition means 12. For example, a discriminator that generates a pulse signal when the output signal of the radiation detection means 11 exceeds a predetermined threshold voltage Vth may be used. The digital data obtained by Analog to Digital Converter) may be processed to generate a signal indicating the rise time T0 (see FIG. 2).

  The waveform acquisition means 13 acquires the waveform of the output signal generated by the radiation incident on the semiconductor 24 and the peak value of this waveform (hereinafter referred to as the peak value). As the waveform acquisition means 13, for example, a Flash-ADC, a multi-channel analyzer, or various circuits constituting these can be used. Various multi-channel analyzers are conventionally known, and any of these can be used. For example, when the waveform acquisition unit 13 is configured by combining a Flash-ADC and an FPGA (Field Programmable Gate Array), the number of times of sampling of the Flash-ADC can be used as time information and a reading of the ADC can be used as peak value information. In the present embodiment, an example in which the signal generation time acquiring means 12 is used to specify the radiation input timing as the rising time T0 has been described, but based on the waveform of the output signal of the waveform acquiring means 13 The control means 34 may specify the rise time T0, and in this case, the radiation detection apparatus 10 may not include the signal generation time acquisition means 12.

  The waveform acquisition means 13 acquires an output signal from the rise time T0 acquired from the signal generation time acquisition means 12 to, for example, an arbitrary time designated by the user, and the waveform and peak value (peak value) of the output signal To get The information on the waveform of the output signal of the radiation detection means 11 acquired by the waveform acquisition means 13 is stored in a storage medium such as the storage means 33 or RAM of the information processing apparatus 14 and used by the processor of the main control means 34, for example. .

  Here, the relationship between the position related information indicating the generation position of the charge in the semiconductor 24 of the detection element 21 and the peak value of the waveform of the output signal of the radiation detection means 11 will be described.

When radiation enters the semiconductor 24, electrons and holes are generated. The number of electrons and holes depends on the energy E of the radiation given to the semiconductor. For example, when TlBr having a band gap of 2.68 eV is used as the semiconductor 24, (E / 2.68) electron / hole pairs are generated. In this case, for example, when all the gamma rays 662 keV of cesium-137 lose energy in the semiconductor 24, about 2.5 × 10 ⁵ electron / hole pairs are generated. In this case, in an ideal state where everything can be obtained as a signal, the statistical error is as small as 0.2%.

  That is, in an ideal state in which all the charges generated in the semiconductor 24 contribute to the output signal of the semiconductor 24 according to the incident energy, the magnitude of the output signal of the radiation detection means 11 is the number of generated electron / hole pairs. Proportional to The number of electron / hole pairs generated is proportional to the energy E of the incident radiation. Therefore, the peak value of the waveform of the output signal of the radiation detection means 11 is a value reflecting the energy of the incident radiation. For this reason, if it is an ideal state in which all of the charges generated in the semiconductor 24 contribute to the output signal of the semiconductor 24 according to the incident energy, the wave height value of the waveform of the output signal of the radiation detection means 11 accurately enters. The energy of radiation can be determined.

  However, in practice, not all of the charge generated in the semiconductor 24 contributes to the output signal of the semiconductor 24, and a part of the charge is trapped in the semiconductor 24 while moving to the electrode, etc. Decrease. For example, assuming that when the electron / hole pair is generated at depth z = Z and the electrons move to the anode 25 and the holes move to the cathode 26, respectively, the electric field is uniformly distributed in the semiconductor 24. , And electrons decrease exponentially as shown by the following equations (1) and (2) as they move.

Where n is the number of generated charges, e ₀ is an elementary charge, μ _e and τ _e are the mobility and average lifetime of electrons in the semiconductor 24 respectively, and μ _h and τ _h are holes in the semiconductor 24 respectively The mobility and the average lifetime of

For example, TlBr is known to be τ _e μ _e to 10 ⁻³ cm ² / V for electrons and τ _h μ _h 10 to 10 ⁻⁴ cm ² / V for holes. When calculated using these, for example, in the case of the thickness d = 5 mm and the applied voltage of 500 V, the peak value changes by about 40% depending on the position. Therefore, when energy is obtained from the peak value measured from the waveform, the energy spectrum draws a large tail on the low energy side. Therefore, in order to obtain high energy resolution, it is important to correct the crest value according to the generation position of the charge in the semiconductor 24.

  FIG. 3 is an explanatory view showing an example of the relationship between the charge generation position and the peak value. In general, the value of τμ of the semiconductor 24 used for the detection element 21 is larger for electrons by about one digit. For this reason, the contribution to the output signal of the radiation detection means 11 is larger in the signal derived from electrons on average.

  Specifically, as shown in FIG. 3, when charge is generated at a position close to the anode 25 to which the electrons move, the peak value (peak value) is higher than that at a position far from the anode 25. The time to reach) is short (hereinafter referred to as peak time).

  On the other hand, as the charge generation position moves away from the anode 25 and approaches the cathode 26, the peak value increases. The reason for this is that although the contribution of the hole signal increases as the charge generation position is closer to the anode 25, the holes drift more as the charge generation position is closer to the anode 25 because the mean free path of the holes is short. It is mentioned that it is lost inside.

  Thus, if the incident radiation energy is the same, the peak value of the waveform of the output signal of the radiation detection means 11 should be the same regardless of the charge generation position in the semiconductor 24. Actually, the radiation detection means 11 The crest value of the waveform of the output signal of H changes according to the charge generation position in the semiconductor 24.

  On the other hand, as shown in FIG. 3, if the incident radiation energy is the same, it can be said that there is a correlation between the charge generation position and the peak value. Therefore, the radiation detection apparatus 10 according to an embodiment of the present invention extracts position related information indicating the generation position of the charge from the waveform of the output signal of the radiation detection means 11, and corrects the peak value using this position related information. Do.

  FIG. 4 is an explanatory view showing an example of the relationship between the peak value Vmax and the peak time Tmax-T0. FIG. 5 (a) is an explanatory view showing an example of how a peak time Tmax-T0 is extracted as position related information from the waveform of the output signal of the radiation detecting means 11, and FIG. 5 (b) is a position from the waveform of the output signal. It is explanatory drawing which shows an example of a mode that T2-T1 during time to which the predetermined | prescribed output signal value V1 is given as related information is extracted.

  The peak time is represented by a time Tmax-T0 from the rise time T0 of the output signal to the time Tmax at which the peak value Vmax is reached (see FIG. 5A). As shown in FIG. 3, as the charge generation position moves away from the anode 25, the peak value Vmax increases and the peak time Tmax-T0 increases. Therefore, the ratio Vmax / (Tmax-T0) between the peak value Vmax actually measured from the waveform and the peak time Tmax-T0 has a correlation as shown in FIG. 4 according to the generation position of the charge.

  Therefore, the information processing apparatus 14 of the radiation detection apparatus 10 according to the first embodiment uses the peak time Tmax-T0 as the position-related information extracted from the waveform of the output signal of the radiation detection means 11 to obtain in advance. The peak value Vmax is corrected using the correction equation or the look-up table, etc.

  The information processing apparatus 14 is constituted of, for example, a general personal computer, a work station or the like, and has an input unit 31, a display unit 32, a storage unit 33, and a main control unit 34.

  The input unit 31 is formed of a general input device such as a keyboard, a touch panel, and a numeric keypad, and outputs an operation input signal corresponding to the user's operation to the main control unit 34.

  The display means 32 is constituted by a general display output device such as a liquid crystal display or an OLED (Organic Light Emitting Diode) display, and the waveform of the output signal or the information of the peak value Vmax or corrected according to the control of the main control means 34 Display various information such as information on the energy of incident radiation obtained using peak values.

  The storage means 33 has a configuration including a processor readable recording medium such as a magnetic or optical recording medium or a semiconductor memory. Some or all of the programs and data in these recording media may be configured to be downloaded by communication via an electronic network. The storage unit 33 stores at least association information in which position related information indicating the generation position of the charge in the semiconductor 24 of the detection element 21 and the ideal peak value are associated in advance.

  The association information stored in the storage unit 33 according to the first embodiment is a correction formula or a look-up table for correcting the peak value Vmax of the waveform so as to approach the ideal peak value using the peak time Tmax-T0. . The correction equation may be, for example, an equation that is inversely proportional to the peak time Tmax−T0, or a variety of equations such as a polynomial function including a quadratic function or an exponential function. The correction formula and the lookup table as association information are generated in advance according to the configuration of the radiation detection apparatus 10 and stored in the storage unit 33.

  The main control means 34 is configured of a storage medium such as a ROM, a processor such as a CPU, a RAM, and the like.

  The processor of the main control means 34 loads the radiation detection program stored in the storage medium such as the ROM and data necessary for the execution of this program into the RAM, and extracts the waveform of the output signal according to the program The processing for obtaining high energy resolution with a simple configuration is performed by correcting the waveform peak value Vmax using the position related information.

  Instead of storing the program in the storage medium, the program may be directly incorporated in the circuit of the processor. In this case, the processor functions as various function implementing means by reading and executing a program incorporated in the circuit. Also, the main control means 34 may be configured by a single processor, and a single processor may realize each function, or a plurality of independent processors may be combined to form a main control means, and each processor may execute a program. Each function may be realized by execution. In addition, when a plurality of processors are provided, storage media for storing programs may be individually provided for each processor, or a single storage medium collectively stores programs corresponding to the functions of all the processors. May be

  The RAM of the main control means 34 provides a work area for temporarily storing programs executed by the CPU and data.

  A storage medium such as the ROM of the main control means 34 stores a start program of the radiation detection apparatus 10, a radiation detection program, and various data necessary for executing these programs.

  A storage medium such as a ROM has a configuration including a recording medium readable by a processor, such as a magnetic or optical storage medium or a semiconductor memory, and a part of programs and data in the storage medium. Alternatively, all may be configured to be downloaded via the electronic network.

  As shown in FIG. 1, the processor of the main control unit 34 functions as at least a correction unit 41 and an energy calculation unit 42 according to a radiation detection program. Each of these function implementing means 41-42 utilizes a required work area of the RAM as a temporary storage place of data. Note that these function implementing means 41-42 may be implemented by hardware logic such as a circuit without using a processor.

  The correction unit 41 extracts, from the waveform of the output signal of the radiation detection unit 11 acquired by the waveform acquisition unit 13, position related information indicating the generation position of the charge in the semiconductor 24 of the detection element 21. The peak value Vmax of the waveform is corrected using the position related information.

  The correction means 41 according to the first embodiment extracts, for example, peak time Tmax-T0 from the waveform as position related information (see FIG. 5A). Then, using the association information stored in the storage unit 33 and the extracted peak time Tmax-T0, the correction unit 41 corrects the waveform peak value Vmax. The association information is a correction formula or a look-up table or the like for correcting the peak value Vmax using the peak time Tmax-T0 so as to approach the ideal peak value.

  As position related information according to the first embodiment, in addition to peak time Tmax-T0, for example, time T2-T1 for giving a predetermined output signal value V1 can be used (FIG. 5 (b)). reference). It can be said that time T2-T1 for giving a predetermined output signal value V1 also has a correlation with the charge generation position, for example, the charge generation position becomes longer as the distance from the anode 25 increases.

  The energy calculating means 42 obtains the energy of the radiation actually incident on the semiconductor 24 on-line in real time using the peak value corrected by the correcting means 41. The crest value used by the energy calculation means 42 is a value obtained by correcting the crest value Vmax according to the generation position of the charge by the correction means 41. For this reason, the energy calculating means 42 can obtain energy very accurately as compared with the case of using the waveform peak value Vmax as it is without considering the generation position of the charge.

  Next, an example of the operation of the radiation detection apparatus 10, the radiation detection method, and the radiation detection program according to an embodiment of the present invention will be described.

  FIG. 6 is a flow chart showing an example of a procedure for correcting the peak value Vmax of the waveform by the main control unit 34 shown in FIG. 1 using the position related information extracted from the waveform of the output signal of the radiation detection unit 11. . In FIG. 6, reference numerals with S attached indicate steps in the flowchart. In this procedure, radiation enters the semiconductor 24 and charges are generated in the semiconductor 24 to start.

  First, in step S1, the waveform acquisition unit 13 acquires the waveform of the output signal of the radiation detection unit 11 from the rise time T0 acquired from the signal generation time acquisition unit 12 to any time specified by the user. Next, in step S2, the waveform acquisition means 13 acquires the peak value Vmax from the waveform.

  Next, in step S3, the correction unit 41 extracts position related information indicating the generation position of the charge in the semiconductor 24 of the detection element 21 from the waveform of the output signal of the radiation detection unit 11 acquired by the waveform acquisition unit 13. Do. In the first embodiment, the correction unit 41 extracts, for example, a peak time Tmax-T0 from the waveform as position related information (see FIG. 5A).

  Next, in step S4, the correction unit 41 reads out and acquires association information between the position related information and the ideal peak value from the storage unit 33. In the first embodiment, the correction unit 41 reads from the storage unit 33 a correction formula, a lookup table, or the like as association information for correcting the peak value Vmax using the peak time Tmax−T0 so as to approach the ideal peak value. .

  Next, in step S5, the correction means 41 corrects the peak value Vmax actually measured from the waveform, using the position related information extracted from the waveform and the association information. In the first embodiment, the correction unit 41 corrects the waveform peak value Vmax using the association information and the peak time Tmax-T0 (see FIG. 4).

  Next, in step S6, the energy calculating unit 42 obtains the energy of the radiation incident on the semiconductor 24 using the corrected peak value.

  According to the above-described procedure, the peak value Vmax of the waveform can be corrected so as to approach the ideal peak value, using the position related information extracted from the waveform of the output signal of the radiation detection means 11. For this reason, the energy calculating means 42 can obtain energy very accurately as compared with the case of using the waveform peak value Vmax as it is without considering the generation position of the charge.

  The radiation detection apparatus 10 according to the first embodiment corrects the crest value Vmax of the waveform by using the peak time Tmax-T0 as position-related information extracted from the waveform by the correction means 41, and the corrected crest value The energy can be determined using For this reason, the radiation detection apparatus 10 can obtain | require energy correctly using the wave height value which correct | amended suitably the shift | offset | difference of the wave height value Vmax according to the generation | occurrence | production position of an electric charge. Therefore, according to the radiation detection apparatus 10, high energy resolution can be obtained with a simple configuration without using a cooling device or a dehumidifier.

Second Embodiment
Next, a second embodiment of a radiation detection apparatus, a radiation detection method, and a radiation detection program according to the present invention will be described.

  The radiation detection apparatus 10 according to the second embodiment differs from the radiation detection apparatus 10 according to the first embodiment in that the generation position Z of the charge is obtained from the output signal waveform of the radiation detection unit 11 and used as position related information. The other configurations and functions are substantially the same as those of the radiation detection apparatus 10 according to the first embodiment shown in FIG.

  FIG. 7 (a) is an explanatory view showing an example of the relationship between the output signal waveform of the radiation detection means 11 and the electron contribution period Te, and FIG. 7 (b) is the relationship between the charge generation position Z and the electron movement distance d-Z. It is a figure for demonstrating.

  The waveform up to the peak time of the output signal of the radiation detection means 11 can be roughly classified into two periods. The first period (hereinafter referred to as the electron contribution period Te) is a period in which contributions of both electrons and holes are obtained, and is a period in which only Te immediately after the rise time T0. The second period is a period after the electron contribution period Te, and is a period in which only the hole contribution is obtained.

  In the electron contribution period Te, since both electrons and holes contribute to the signal, the signal amount is larger than in the second period in which only the hole contribution is made. Therefore, the time change of the output signal of the charge amplifier 23 in the first period is larger than that of the output signal in the second period.

  Therefore, the electron contribution period Te can be obtained by determining the time Te + T0 at which the time change amount ΔVi / ΔTi of the output signal of the waveform becomes equal to or less than the predetermined time change amount.

The electron contribution period Te can be estimated to give the time taken for all electrons generated in the semiconductor 24 to reach the anode 25. Electronic drift distance, the thickness of the semiconductor 24 d, when the occurrence location of a charge Z, and the electric field E1, written as _{d-Z = μ e · E1} · Te. Since the electron mobility μ _e is known, the charge generation position Z can be obtained from the electron contribution period Te.

  Therefore, the information processing apparatus 14 of the radiation detection apparatus 10 according to the second embodiment is previously obtained using the charge generation position Z as position related information extracted from the waveform of the output signal of the radiation detection means 11. The peak value Vmax is corrected using a correction equation or a look-up table.

  The association information stored in the storage unit 33 according to the second embodiment is a correction formula or a look-up table for correcting the waveform peak value Vmax so as to approach the ideal peak value using the charge generation position Z. .

The correction means 41 according to the second embodiment extracts the electron contribution period Te from the waveform, and based on the electron contribution period Te extracted from this waveform and the electron mobility μ _{e of the} semiconductor 24, as position related information The generation position Z of the charge is determined. The correction unit 41 corrects the waveform peak value Vmax using the charge generation position Z obtained from the waveform and the association information stored in the storage unit 33. The association information is a correction formula or a look-up table for correcting the peak value Vmax using the charge generation position Z so as to approach the ideal peak value.

  In the radiation detection apparatus 10 according to the second embodiment, the correction unit 41 corrects the waveform peak value Vmax using the charge generation position Z as position-related information extracted from the waveform, and the corrected peak value The energy can be determined using For this reason, the radiation detection apparatus 10 according to the second embodiment uses a peak value obtained by appropriately correcting the shift of the peak value Vmax according to the generation position of the charge, similarly to the radiation detection apparatus 10 according to the first embodiment. Energy can be determined accurately. Therefore, according to the radiation detection apparatus 10 according to the second embodiment, high energy resolution can be obtained with a simple configuration without using a cooling device or a dehumidifier.

Third Embodiment
FIG. 8 is a block diagram showing an example of a radiation detection apparatus 10 according to the third embodiment of the present invention. The radiation detection apparatus 10 according to the third embodiment corrects the wave height value Vmax in accordance with the temperature of the semiconductor 24. The radiation detection apparatus 10 according to the first embodiment is further provided with a temperature measuring unit 51 for measuring the temperature of the semiconductor 24. It differs from the radiation detection apparatus 10 which concerns. The other configurations and functions are substantially the same as those of the radiation detection apparatus 10 according to the first embodiment shown in FIG.

  The radiation detection apparatus 10 according to the third embodiment includes a temperature measurement unit 51 that measures the temperature of the semiconductor 24. As the temperature measurement means 51, a thermocouple thermometer, a semiconductor thermometer, a resistance temperature detector, etc. can be used.

  The mobility μ and the average lifetime τ of the charge of the semiconductor 24 depend on the temperature. For this reason, the radiation detection apparatus 10 according to the present embodiment corrects the crest value Vmax in accordance with the temperature of the semiconductor 24 measured by the temperature measurement unit 51.

  Specifically, the association information stored in the storage unit 33 according to the third embodiment is a correction formula or a look-up table according to the temperature of the semiconductor 24.

  The correction unit 41 according to the third embodiment corrects the crest value Vmax of the waveform using the temperature of the semiconductor 24 acquired from the temperature measurement unit 51 and the association information stored in the storage unit 33. For example, when the peak time Tmax-T0 is used as position related information as described in the first embodiment, the association information includes the temperature of the semiconductor 24, the peak time Tmax-T0, and the peak value Vmax of the waveform. It is a correction formula or a lookup table in which the ideal peak values are associated with one another. In the case where the charge generation position Z is used as position related information as described in the second embodiment, the association information includes the temperature of the semiconductor 24, the charge generation position Z, the peak value Vmax of the waveform, and the ideal wave. It is a correction expression or a look-up table in which high values are associated with one another.

Furthermore, when the charge generation position Z is used as position related information as shown in the second embodiment, the correction means 41 according to the third embodiment generates the charge after extracting the electron contribution period Te from the waveform. when obtaining the position Z, it may be used electron mobility mu _e in accordance with the temperature of the semiconductor 24. In this case, the estimation accuracy of the charge generation position Z can be improved, and the energy resolution can be further enhanced.

  The radiation detection apparatus 10 according to the third embodiment has the same effects as the radiation detection apparatus 10 according to the first embodiment and the radiation detection apparatus 10 according to the second embodiment. Moreover, since the radiation detection apparatus 10 according to the third embodiment can correct the wave height value Vmax in accordance with the temperature of the semiconductor 24, energy can be determined more accurately.

Fourth Embodiment
FIG. 9 is a block diagram showing an example of a radiation detection apparatus 10 according to the fourth embodiment of the present invention. The radiation detection device 10 according to the fourth embodiment differs from the radiation detection device 10 according to the third embodiment in that the temperature of the semiconductor 24 is controlled. The other configurations and functions are substantially the same as those of the radiation detection apparatus 10 according to the third embodiment shown in FIG.

  The radiation detection apparatus 10 according to the fourth embodiment includes a temperature adjustment unit 52 controlled by the main control unit 34 to adjust the temperature of the semiconductor 24. Various kinds of temperature control means 52 such as a Peltier element, a heater, and a fan are conventionally known, and any one of them can be used.

  The processor of the main control means 34 according to the fourth embodiment further functions as a temperature control means 61 according to the radiation detection program. The temperature control means 61 controls the temperature adjustment means 52 to keep the temperature of the semiconductor 24 constant, for example, according to the temperature of the semiconductor 24 measured by the temperature measurement means 51.

  The radiation detection apparatus 10 according to the fourth embodiment has the same effects as the radiation detection apparatus 10 according to the third embodiment. The radiation detection apparatus 10 according to the fourth embodiment includes, for example, the temperature of the semiconductor 24 at the time of obtaining the association information shown in the first embodiment and the second embodiment in advance, and the temperature of the semiconductor 24 at the time of signal measurement. Can be matched. Therefore, according to the radiation detection apparatus 10 according to the fourth embodiment, the accuracy of the correction of the wave height value Vmax can be further improved, and the energy resolution can be further improved.

Fifth Embodiment
FIG. 10 is a block diagram showing an example of a radiation detection apparatus 10 according to the fifth embodiment of the present invention. The radiation detection device 10 according to the fifth embodiment differs from the radiation detection device 10 according to the first embodiment in that the shape of the anode 25 is a pixel type. The other configurations and functions are substantially the same as those of the radiation detection apparatus 10 according to the first embodiment shown in FIG.

  The anode 25 of the radiation detection device 10 according to the fifth embodiment is a so-called pixel electrode. In this case, the anode 25 is divided, for example, into a plurality of electrode elements 25a which are divided in one vertical or horizontal direction and arranged in one dimension of 1 × k (where k is a positive integer), or divided in two vertical and horizontal directions. It is constituted by a plurality of electrode elements 25a arranged in two dimensions of m × n (where m and n are positive integers). The anode 25 as the pixel electrode can be formed, for example, by sputtering. In addition, the anode 25 may further include a guard ring electrode for reducing the leakage current from the side surface. The guard link electrode is provided, for example, to surround the entire outer periphery of the plurality of electrode elements 25a.

  When parallel plate electrodes of the same shape are attached to both sides of the crystal of the semiconductor 24, the electric field gradient is uniform inside the semiconductor 24. On the other hand, when one of the electrodes is a pixel electrode, the electric field gradient on the pixel electrode side can be increased.

  For example, when the anode 25 is a pixel electrode, the electric field gradient is large around the anode 25. For this reason, electrons moving to the anode 25 move more easily, and holes moving to the cathode 26 become harder to move. Therefore, by using the anode 25 as a pixel electrode, it is possible to selectively acquire a signal of electrons having a relatively long life, and the influence of holes whose contribution to the signal is largely changed depending on the position of charge generation is output. It can be significantly reduced from the signal.

  The radiation detection apparatus 10 according to the fifth embodiment can be combined with each of the radiation detection apparatus 10 according to the first to fourth embodiments, and the same effects can be obtained. In addition, the radiation detection device 10 according to the fifth embodiment can reduce the influence of holes on the output signal, so that the charge generation position dependency of the wave height value Vmax of the waveform can be reduced, and thus more accurately. You can ask for energy.

  According to at least one embodiment described above, the peak value Vmax of the waveform is corrected using the position related information extracted from the waveform of the output signal of the radiation detection means 11, and the energy is determined using the corrected peak value. Therefore, high energy resolution can be obtained with a simple configuration.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 10 ... Radiation detection apparatus, 11 ... Radiation detection means, 24 ... Semiconductor, 25 ... Anode, 41 ... Correction means, 42 ... Energy calculation means, 51 ... Temperature measurement means, 61 ... Temperature control means, E ... Energy, T0 ... Rise Time, Te ... electron contribution period, Tmax-T0 ... peak time, Vmax ... peak value, Z ... charge generation position.

Claims (11)

Correction for correcting the crest value of the waveform of the output signal using position related information indicating the generation position of the charge extracted from the output signal output based on the charge generated according to the energy of the radiation incident on the semiconductor Means,
Energy calculating means for obtaining energy of the radiation incident on the semiconductor using the peak value corrected by the correcting means;
Radiation detector equipped with The correction means is
The peak value is corrected based on association information in which the peak value and position related information are associated in advance.
The radiation detection device according to claim 1. The position related information is
A peak time which is a time from a rising time to a time when the waveform of the output signal reaches the peak value;
The radiation detection device according to claim 2. The association information is
Using the ratio of the peak value of the waveform to the peak time,
The radiation detection apparatus according to claim 3. The position related information is
An electron contribution period which is a period from the rise time of the waveform of the output signal to the time when the waveform becomes less than or equal to a predetermined time change amount,
The radiation detection device according to claim 2. Temperature measuring means for measuring the temperature of the semiconductor;
And further
The correction means is
Correcting the peak value of the waveform further using the temperature of the semiconductor measured by the temperature measuring means;
The radiation detection apparatus according to any one of claims 1 to 5. Temperature control means for controlling the temperature of the semiconductor to be maintained at a predetermined temperature;
The radiation detection apparatus according to any one of claims 1 to 6, further comprising: The semiconductor is a compound semiconductor,
The radiation detection apparatus according to any one of claims 1 to 7. Radiation detecting means for outputting the output signal;
The radiation detection apparatus according to any one of claims 1 to 8, further comprising: Extracting position-related information indicating a generation position of the charge from the waveform of a signal output based on the charge generated according to the energy of the radiation incident on the semiconductor;
Correcting the peak value of the waveform using the position related information;
Determining the energy of the radiation incident on the semiconductor using the corrected peak value;
Radiation detection method. On the computer
Extracting position-related information indicating a generation position of the charge from the waveform of a signal output based on the charge generated according to the energy of the radiation incident on the semiconductor;
Correcting the peak value of the waveform using the position related information;
Determining the energy of the radiation incident on the semiconductor using the corrected peak value;
Radiation detection program for running

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