Signal processing method, radiation detection device, and computer program

Abstract

To provide a signal processing method, radiation detection device and computer program that enable sufficient suppression of degradation of accuracy of radiation detection.SOLUTION: A signal processing method is provided, using: a semiconductor portion; a single first electrode collecting electric charges generating inside the semiconductor portion by radiation made incident on the semiconductor portion; a second electrode to which voltage is applied and which consequently generates an electric field for focusing the electric charge on the first electrode; and a signal output unit outputting a signal including a staircase wave having a wave height corresponding to an amount of the electric charge collected by the first electrode, the signal processing method thereby processing the signal output by the signal output unit, wherein the semiconductor portion has a specific area in which intensity of the electric field is lower than other area, determines whether the staircase wave is caused by the electric charge generated in the specific area on the basis of a shape of the staircase wave, counts the staircase wave by the wave height when the staircase wave is not caused by the electric charge generated in the specific area, and does not count the staircase wave when the staircase wave is caused by the electric charge generated in the specific area.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a signal processing method, a radiation detection apparatus, and a computer program for processing a signal generated by detection of radiation. [Background technology]

[0002] Some radiation detectors for detecting radiation such as X-rays include a radiation detection element using a semiconductor. The radiation detection element using a semiconductor includes a flat semiconductor part. The semiconductor body is provided with a first electrode for signal output and a second electrode for voltage application arranged on the back side of the first electrode. When a voltage is applied, an electric field is generated between the first electrode and the second electrode. When radiation is incident on the semiconductor part, a number of electron-hole pairs corresponding to the energy of the radiation are generated, the electrons and the holes move according to the electric field, the electrons are collected at the first electrode, and a signal corresponding to the charge amount of the electrons is output from the first electrode. The charge amount corresponds to the energy of the radiation, and the first electrode outputs a signal corresponding to the energy of the radiation. Patent Document 1 discloses a radiation detection element including a plurality of first electrodes and second electrodes.

[0003] In a radiation detection element with a single first electrode, the semiconductor portion has parts with high and low electric field strength. For example, the first electrode is provided in the center of one surface of the semiconductor portion, and the parts close to the outer edge of the semiconductor portion are far from the first electrode and have low electric field strength. When radiation is incident on a part with low electric field strength, the generated electrons spread out and it takes time for the electrons to gather at the first electrode. Also, not all the electrons are gathered, the charge amount decreases, and the energy of the radiation may be detected as low. This reduces the accuracy of radiation detection.

[0004] Conventionally, a radiation detector includes a collimator. The collimator blocks radiation that is about to enter a portion of the semiconductor portion where the electric field strength is low, and passes radiation that is about to enter a portion of the semiconductor portion where the electric field strength is high. The collimator prevents radiation from entering the portion of the semiconductor portion where the electric field strength is low, and suppresses a decrease in the accuracy of radiation detection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6159133 Summary of the Invention [Problem to be solved by the invention]

[0006] High-energy radiation may pass through a collimator. The radiation that passes through the collimator enters a portion of the semiconductor section where the electric field strength is low, reducing the accuracy of radiation detection. For this reason, conventional radiation detectors have been unable to sufficiently prevent the reduction in accuracy of radiation detection.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a signal processing method, a radiation detection device, and a computer program that can sufficiently suppress a decrease in the accuracy of radiation detection. [Means for solving the problem]

[0008] A signal processing method according to the present invention uses a semiconductor section, a single first electrode provided in the semiconductor section for collecting charges generated within the semiconductor section due to radiation incident on the semiconductor section, a second electrode provided in the semiconductor section for generating an electric field for concentrating the charges within the semiconductor section at the first electrode by application of a voltage, and a signal output section for outputting a signal including a step wave having a wave height corresponding to the amount of charge collected by the first electrode, and processes a signal output by the signal output section, the semiconductor section having a singular region where the intensity of the electric field is lower than in other regions, and based on the shape of the step wave, it is determined whether the step wave is caused by charges generated in the singular region, and if the step wave is not caused by charges generated in the singular region, the step wave is counted by wave height, and if the step wave is caused by charges generated in the singular region, the step wave is not counted.

[0009] In one embodiment of the present invention, charges generated by radiation incident on the semiconductor part are collected by a single first electrode, and an electric field is generated in the semiconductor part by applying a voltage to the second electrode, and the electric field causes the charges to concentrate on the first electrode, and a signal including a step wave having a wave height according to the amount of the charges is output from the signal output part. The semiconductor part has a peculiar region where the intensity of the electric field is lower than in other regions. Whether or not the step wave is caused by the charges generated in the peculiar region is determined based on the shape of the step wave. If the step wave is not caused by the charges generated in the peculiar region, the step wave is counted according to the wave height, and if the step wave is caused by the charges generated in the peculiar region, the step wave is not counted. Since the intensity of the electric field is low in the peculiar region, the charges generated by the radiation are diffused, and the amount of charge collected by the first electrode is reduced. The amount of charge corresponds to the energy of the radiation, and the energy of the radiation is underdetected by the reduction in the amount of charge. By not counting the step wave caused by the charges generated in the peculiar region, the energy of the radiation is prevented from being underdetected.

[0010] The signal processing method of the present invention is characterized in that, when the length of time corresponding to the feature is long, with a predetermined threshold as the boundary, it is determined that the step wave is caused by charges generated in the anomalous region, and the threshold is determined for each wave height so that the length of time corresponding to the threshold increases monotonically as the wave height of the step wave increases.

[0011] In one embodiment of the present invention, based on a feature value corresponding to the length of time the step wave continues, it is determined that the step wave is caused by charges generated in the unique region when the length of time corresponding to the feature value is long, with a predetermined threshold as the boundary. The threshold value is determined for each wave height so that the length of time corresponding to the threshold value increases monotonically with an increase in the wave height of the step wave. The wave height of the step wave corresponds to the energy of the radiation. The greater the energy of the radiation incident on the semiconductor part, the more likely the charge will spread over a wide region, and the longer the time the step wave will continue. By determining the threshold value as described above, it is possible to accurately determine whether the step wave is caused by charges generated in the unique region.

[0012] The signal processing method according to the present invention is characterized in that a feature corresponding to the length of time that the step wave continues is measured, the feature is corrected in accordance with the height of the step wave so that the length of time corresponding to the corrected feature value monotonically decreases as the height of the step wave increases, and based on the corrected feature value, a predetermined constant threshold value is used as a boundary to determine that the step wave is caused by charges generated in the singular region.

[0013] In one embodiment of the present invention, a feature value corresponding to the duration of the step wave is measured, the feature value is corrected according to the wave height of the step wave, and when the duration of the corrected feature value is long with respect to a certain threshold value, it is determined that the step wave is caused by the charge generated in the unique region. The feature value is corrected so that the duration of the feature value monotonically decreases with an increase in the wave height of the step wave. The greater the energy of the radiation incident on the semiconductor part, the longer the duration of the step wave, so by correcting the feature value as described above, it is possible to accurately determine whether the step wave is caused by the charge generated in the unique region.

[0014] In the signal processing method according to the present invention, the feature amount is a time width of the step wave.

[0015] In one embodiment of the present invention, the characteristic amount of the staircase wave is a time width of the staircase wave. The time width corresponds to the length of time that the staircase wave continues. When the time width is long, it is determined that the staircase wave is caused by charges generated in the unique region.

[0016] In the signal processing method according to the present invention, the feature amount is a maximum value of the slope of the step wave.

[0017] In one embodiment of the present invention, the characteristic amount of the staircase wave is the maximum value of the slope of the staircase wave. The longer the time width of the staircase wave, the smaller the maximum value of the slope of the staircase wave, and the shorter the time width of the staircase wave, the larger the maximum value of the slope of the staircase wave. Therefore, the maximum value of the slope of the staircase wave corresponds to the time the staircase wave continues. When the maximum value of the slope of the staircase wave is small, it is determined that the staircase wave is caused by charges generated in the unique region.

[0018] In the signal processing method according to the present invention, the feature amount is a value of a second-order differential of the step wave at a point in time when the differential value of the step wave reaches a predetermined reference value.

[0019] In one embodiment of the present invention, the characteristic amount of the staircase wave is the value of the second-order differential at the time when the differential value of the staircase wave becomes a predetermined reference value. When the time required for the electric charge generated by radiation to flow into the first electrode is long, the differential waveform of the staircase wave rises gently, and the slope of the rising edge of the differential waveform becomes small. Conversely, when the time required for the electric charge to flow into the first electrode is short, the differential waveform of the staircase wave rises steeply, and the slope of the rising edge of the differential waveform becomes large. Therefore, the slope of the rising edge of the differential waveform of the staircase wave corresponds to the time the staircase wave continues. The slope of the rising edge of the differential waveform is the value of the second-order differential at the time when the differential value of the staircase wave becomes a predetermined reference value. When the value of the second-order differential at the time when the differential value of the staircase wave becomes the reference value is small, it is determined that the staircase wave is caused by the electric charge generated in the unique region.

[0020] A radiation detection device according to the present invention includes a radiation detection element, a signal output unit that outputs a signal corresponding to radiation incident on the radiation detection element, and a signal processing device that processes the signal output by the signal output unit, wherein the radiation detection element includes a semiconductor portion, a single first electrode provided in the semiconductor portion for collecting charges generated in the semiconductor portion by radiation incident on the semiconductor portion, and a second electrode provided in the semiconductor portion for generating an electric field within the semiconductor portion for concentrating the charges on the first electrode by application of a voltage, the signal output unit outputs a signal including a step wave having a wave height corresponding to an amount of charge collected by the first electrode, and the semiconductor portion has a singular region where the intensity of the electric field is lower than in other regions, and the signal processing device determines whether the step wave is caused by charges generated in the singular region based on a shape of the step wave, and if the step wave is not caused by charges generated in the singular region, counts the step wave by wave height, and does not count the step wave if the step wave is caused by charges generated in the singular region.

[0021] In one embodiment of the present invention, a radiation detection device includes a radiation detection element having a semiconductor portion, a single first electrode, and a second electrode, a signal output portion, and a signal processing device. The signal processing device determines whether or not the step wave is caused by charges generated in the unique region, and counts the step wave by wave height when the step wave is not caused by charges generated in the unique region, and does not count the step wave when the step wave is caused by charges generated in the unique region. In this way, the radiation detection device prevents underdetection of radiation energy by not counting radiation whose energy is detected as being underestimated.

[0022] The radiation detection device according to the present invention is characterized in that it does not include a collimator that blocks a part of the radiation incident on the semiconductor portion.

[0023] According to an aspect of the present invention, the radiation detection device does not include a collimator. Even without using a collimator, it is possible to prevent the energy of radiation from being detected as being too low, and to suppress a decrease in the accuracy of radiation detection.

[0024] The radiation detection device of the present invention is characterized in that it further comprises an irradiation unit that irradiates a sample with radiation, a spectrum generation unit that generates a spectrum of radiation representing the relationship between the number of counts counted by the signal processing device and pulse height, and a display unit that displays the spectrum generated by the spectrum generation unit.

[0025] In one aspect of the present invention, the radiation detection device generates a spectrum of radiation. The spectrum of radiation whose energy is detected almost accurately is generated and displayed on a display unit.

[0026] A computer program according to the present invention is a computer program that causes a computer to process a signal output using a semiconductor section, a single first electrode provided in the semiconductor section that collects charges generated within the semiconductor section by radiation incident on the semiconductor section, a second electrode provided in the semiconductor section that generates an electric field for concentrating the charges within the semiconductor section at the first electrode by application of a voltage, and a signal output section that outputs a signal including a step wave having a wave height corresponding to the amount of charge collected by the first electrode, and is characterized in that the computer is caused to execute a process of counting the step wave by wave height when it is determined based on the shape of the step wave that the step wave is not caused by charges generated in a unique region in the semiconductor section where the intensity of the electric field is lower than in other regions, and not counting the step wave by wave height when it is determined that the step wave is caused by charges generated in the unique region, and generating a spectrum of radiation representing the relationship between the number of counts of the step wave and the wave height.

[0027] In one embodiment of the present invention, a radiation spectrum is generated by using a computer in accordance with a computer program to count step waves not caused by charges generated in the peculiar region by wave height and not counting step waves caused by charges generated in the peculiar region. Even when the signal processing device does not count the step waves and the computer counts the step waves, a radiation spectrum in which energy is detected almost accurately is generated. Effect of the Invention

[0028] The present invention has an excellent effect of preventing the radiation energy from being detected as being too low, and thereby sufficiently suppressing a decrease in the accuracy of radiation detection. [Brief description of the drawings]

[0029] [Figure 1] 2 is a block diagram showing an example of a functional configuration of the radiation detection apparatus; [Diagram 2] 1 is a schematic cross-sectional view showing an example of a radiation detection element. [Diagram 3] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a radiation detector. [Figure 4] 4 is a graph showing a schematic diagram of the electric field intensity inside a semiconductor portion. [Diagram 5] 1 is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to a first embodiment. [Figure 6] 1 is a schematic graph showing an example of a signal including a step wave. [Figure 7] 1 is a schematic graph showing an example of a step wave having a long duration. [Figure 8] 11 is a schematic graph showing an example of a step wave and its differential waveform for explaining a feature amount. [Figure 9] FIG. 2 is a block diagram showing an example of the internal configuration of an analysis device. [Figure 10] 4 is a flowchart showing a procedure of processing executed by the signal processing device according to the first embodiment. [Figure 11] FIG. 11 is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to a second embodiment. [Figure 12] 10 is a flowchart showing the procedure of a process executed by a signal processing device and an analysis device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention will now be described in detail with reference to the drawings showing embodiments thereof. <Embodiment 1> 1 is a block diagram showing an example of a functional configuration of a radiation detection device 10. The radiation detection device 10 is, for example, an X-ray fluorescence analysis device. The radiation detection device 10 includes an irradiation unit 54 that irradiates a sample 62 with radiation such as an electron beam or X-rays, a sample stage 61 on which the sample 62 is placed, and a radiation detector 2. Radiation is irradiated from the irradiation unit 54 to the sample 62, radiation such as fluorescent X-rays is generated in the sample 62, and the radiation detector 2 detects the radiation generated from the sample 62. In the figure, the radiation is indicated by arrows. Note that the radiation detection device 10 may be configured to hold the sample 62 by a method other than placing the sample 62 on the sample stage 61.

[0031] The radiation detector 2 includes a radiation detection element 1 and a preamplifier 21. A signal processing device 3 and a voltage application unit 51 that applies a voltage required for radiation detection to the radiation detection element 1 are connected to the radiation detector 2. An analysis device 4 is connected to the signal processing device 3. The signal processing device 3, the analysis device 4, the voltage application unit 51, and the irradiation unit 54 are connected to a control unit 52. The control unit 52 controls the operations of the signal processing device 3, the analysis device 4, the voltage application unit 51, and the irradiation unit 54. A display unit 53 such as a liquid crystal display or an EL display (Electroluminescent Display) is connected to the analysis device 4. The control unit 52 may be configured to receive an operation from a user and control each unit of the radiation detection device 10 in response to the received operation.

[0032] FIG. 2 is a schematic cross-sectional view showing an example of the radiation detection element 1. The radiation detection element 1 is a silicon drift type radiation detection element. The radiation detection element 1 is generally flat. The radiation detection element 1 includes a disk-shaped semiconductor portion 11 made of Si (silicon). The semiconductor portion 11 is composed of n-type Si. The semiconductor portion 11 has a first surface 111 and a second surface 112 located on the rear side of the first surface 111. The second surface 112 is a surface located on the incident side where the radiation to be detected is incident.

[0033] The first electrode 12, which is an electrode that outputs a signal when radiation is detected, is provided at the center of the first surface 111. The number of the first electrodes 12 is single. The component of the first electrode 12 is Si of the same type as that of the semiconductor portion 11. For example, the component of the first electrode 12 is n+Si in which a specific dopant such as phosphorus is doped into Si. In addition, the first surface 111 is provided with a plurality of curved electrodes 14 in a multiple ring shape. The component of the curved electrode 14 is a semiconductor of a different type from that of the semiconductor portion 11, and is p-type Si in which a specific dopant such as boron is doped into Si. For example, the component of the curved electrode 14 is p+Si. The curved electrodes 14 arranged in a ring shape are approximately concentric, and the first electrode 12 is located approximately at the center of the curved electrodes 14. That is, the curved electrodes 14 surround the first electrode 12, and the distances between the first electrode 12 and each curved electrode 14 are different.

[0034] 2 shows five curved electrodes 14, more curved electrodes 14 may be provided. The shape of the curved electrodes 14 may be a modified ring, and the multiple curved electrodes 14 do not have to be concentric. The first electrode 12 may be disposed at a position other than the center of the multiple curved electrodes 14, and may be disposed at a position other than the center of the first surface 111.

[0035] An annular guard electrode 151 is provided outside the multiple curved electrodes 14, and an annular ground electrode 152 is provided outside the guard electrode 151. The ground electrode 152 is connected to a ground potential. The potential of the guard electrode 151 is a floating potential. The guard electrode 151 prevents dielectric breakdown between the curved electrodes 14 and the ground electrode 152. Although a single guard electrode 151 is shown in FIG. 2, in reality, multiple guard electrodes 151 are provided in multiple rings.

[0036] A second electrode 13, which is an electrode to which a voltage is applied, is formed on the second surface 112. The second electrode 13 is doped with a dopant that makes Si a semiconductor of a different type from the components of the semiconductor portion 11. The component of the second electrode 13 is p-type Si doped with a specific dopant such as boron, for example, p+Si. The second electrode 13 is formed on most of the area of ​​the second surface 112 including the center of the second surface 112.

[0037] An annular guard electrode 16 is provided on the outside of the second electrode 13. The potential of the guard electrode 16 is a floating potential. Although a single guard electrode 16 is shown in FIG. 2, a plurality of guard electrodes 16 are provided in a multiple annular shape in reality. The guard electrode 16 prevents dielectric breakdown between the edge of the semiconductor portion 11 and the second electrode 13. The radiation detection element 1 may have a configuration in which the ground electrode 152 is not provided on the first surface 111 side, but is provided on the second surface 112 side. That is, the ground electrode 152 may not be provided, and a ground electrode may be provided on the outside of the guard electrode 16. In this configuration, the guard electrode 16 prevents dielectric breakdown between the second electrode 13 and the ground electrode. The radiation detection element 1 may have a configuration in which the ground electrodes are provided on both the first surface 111 side and the second surface 112 side.

[0038] The curved electrodes 14 are connected to a voltage application unit 51. The voltage application unit 51 applies a voltage to the curved electrodes 14 so that the potential of the innermost curved electrode 14 is the highest and the potential of the outermost curved electrode 14 is the lowest. The radiation detection element 1 is configured so that a predetermined electrical resistance is generated between the curved electrodes 14 that are adjacent to each other and have different distances from the first electrode 12. For example, an electrical resistance channel that connects the two curved electrodes 14 is formed by adjusting the components of the portion located between the adjacent curved electrodes 14. That is, the curved electrodes 14 are connected in a daisy chain through electrical resistance. By applying a voltage from the voltage application unit 51, each curved electrode 14 has an electrical potential that monotonically increases in sequence from the outer curved electrode 14 to the inner curved electrode 14. That is, the electrical potential of the curved electrodes 14 increases in sequence from the curved electrode 14 farthest from the first electrode 12 to the curved electrode 14 closest to the first electrode 12. The plurality of curved electrodes 14 may include a pair of adjacent curved electrodes 14 having the same potential.

[0039] The potentials of the multiple curved electrodes 14 generate an electric field (potential gradient) in the semiconductor portion 11 such that the potential is higher in a stepwise manner closer to the first electrode 12 and the potential is lower in a stepwise manner farther from the first electrode 12. The second electrode 13 is connected to a voltage application unit 51. The voltage application unit 51 applies a voltage to the second electrode 13 so that the potential of the second electrode 13 becomes the potential between the innermost curved electrode 14 and the outermost curved electrode 14. In this way, an electric field is generated inside the semiconductor portion 11 such that the potential is higher in a stepwise manner closer to the first electrode 12.

[0040] Radiation such as X-rays, photons in general (including UV and visible light), electron beams, or other charged particle beams is incident on the radiation detection element 1. The radiation is incident mainly from the second surface 112 side into the semiconductor portion 11. An amount of charge corresponding to the energy of the radiation absorbed in the semiconductor portion 11 is generated in the semiconductor portion 11. The generated charges are electrons and holes. The generated charges move due to the electric field inside the semiconductor portion 11, and one type of charge flows into the first electrode 12 in a concentrated manner. In this embodiment, electrons generated by the incidence of radiation move and flow into the first electrode 12. In this way, the first electrode 12 collects electrons generated in the semiconductor portion 11 by the radiation incident on the semiconductor portion 11. A current signal corresponding to the amount of charge of the electrons flowing into the first electrode 12 is output from the first electrode 12.

[0041] A preamplifier 21 is connected to the first electrode 12. A signal output by the first electrode 12 is input to the preamplifier 21. The preamplifier 21 converts the current signal into a voltage signal and outputs the voltage signal. The signal output by the preamplifier 21 has an intensity according to the charge of the electrons collected by the first electrode 12. Since an amount of electrons according to the energy of the radiation is generated and the first electrode 12 collects the generated electrons, the preamplifier 21 outputs a signal with an intensity according to the energy of the radiation. Note that a part of the preamplifier 21 may be included inside the radiation detector 2, and the other part may be disposed outside the radiation detector 2.

[0042] FIG. 3 is a schematic cross-sectional view showing a configuration example of the radiation detector 2. The radiation detector 2 is an SDD (Silicon Drift Detector). The radiation detector 2 includes a housing 23 having a shape of a cylinder with a truncated cone connected to one end. The housing 23 is configured by covering a plate-shaped bottom plate with a cap-shaped cover. A window 24 made of a window material that transmits radiation is provided at the tip of the housing 23. The radiation detection element 1, the substrate 22, the cooling unit 25, and the cold finger 26 are arranged inside the housing 23. The housing 23 accommodates the radiation detection element 1, the substrate 22, and the cooling unit 25. The cooling unit 25 is, for example, a Peltier element.

[0043] The radiation detection element 1 is mounted on the surface of the substrate 22 and disposed at a position facing the window 24. The radiation detection element 1 is disposed so that a first surface 111 faces the substrate 22 and a second surface 112 faces the window 24. Wiring is formed on the substrate 22, and a preamplifier 21 is mounted on the substrate 22. The preamplifier 21 is omitted in FIG. 3. The substrate 22 is in thermal contact with a heat absorbing portion of the cooling unit 25 directly or via an intermediate material. The heat dissipating portion of the cooling unit 25 is in thermal contact with the cold finger 26. The cold finger 26 has a flat portion with which the heat dissipating portion of the cooling unit 25 is in thermal contact, and a portion penetrating the bottom plate portion of the housing 23. The heat of the radiation detection element 1 is absorbed by the cooling unit 25 through the substrate 22, transferred from the cooling unit 25 to the cold finger 26, and dissipated to the outside of the radiation detector 2 through the cold finger 26.

[0044] The radiation detector 2 may not include the cold finger 26, and the heat dissipation portion of the cooling unit 25 may be in thermal contact with the bottom plate portion of the housing 23. The radiation detector 2 may be in a form not including the cooling unit 25. The radiation detector 2 may be in a form not including the window 24 made of a window material, and the portion of the housing 23 corresponding to the window 24 may be open. Alternatively, the radiation detector 2 may be in a form not including the housing 23.

[0045] The radiation detector 2 includes a plurality of lead pins 27 penetrating the bottom plate portion of the housing 23. The lead pins 27 are connected to the substrate 22 by a method such as wire bonding. The application of voltage to the radiation detection element 1 by the voltage application unit 51 and the output of a signal from the preamplifier 21 are performed through the lead pins 27. The radiation detector 2 may further include other components.

[0046] In this embodiment, the radiation detector 2 does not include a collimator that blocks a portion of the radiation incident on the radiation detection element 1. For this reason, radiation can be incident on the entire semiconductor portion 11 that the radiation detection element 1 includes.

[0047] As shown in FIG. 2, the semiconductor part 11 includes a main region 113 and a unique region 114. The main region 113 occupies most of the semiconductor part 11 including the center of the semiconductor part 11, and includes the centers of the first surface 111 and the second surface 112. The main region 113 also includes at least a portion where the first electrode 12 is provided and most of a portion where the second electrode 13 and the curved electrode 14 are provided. The unique region 114 is located around the main region 113 and is a portion close to the outer edge of the semiconductor part 11. For example, the main region 113 is columnar, and the unique region 114 is cylindrical. The distance from the first electrode 12 to the unique region 114 is longer than the distance from the first electrode 12 to the main region 113. The portion of the semiconductor part 11 other than the unique region 114 is the main region 113.

[0048] FIG. 4 is a graph showing a schematic diagram of the electric field intensity inside the semiconductor portion 11. The horizontal axis in the diagram shows the position inside the semiconductor portion 11 in the direction along the first surface 111. The center shown in the diagram is a position on the line connecting the center of the first surface 111 and the center of the semiconductor portion 11. The outer edge shown in the diagram is the position of the outer edge of the semiconductor portion 11. The vertical axis in the diagram shows the electric field intensity. FIG. 4 shows the electric field intensity on a straight line inside the semiconductor portion 11 that is parallel to the first surface 111 and passes through the center. The region including the center is the main region 113, and the region close to the outer edge is the unique region 114.

[0049] The center of the first surface 111 is where the first electrode 12 is provided, and the closer to the center, the closer to the first electrode 12. The closer to the center (the closer to the first electrode 12), the higher the electric field strength. In the main region 113, the electric field strength is sufficiently high. Electrons (one type of charge) among the charges generated in the main region 113 by the incidence of radiation flow quickly into the first electrode 12 due to the high electric field. As a result, the first electrode 12 collects almost all of the generated electrons in a short period of time. Since the amount of charge of the electrons collected by the first electrode 12 corresponds to the energy of the radiation, the energy of the radiation incident on the main region 113 is detected almost accurately.

[0050] The distance from each part in the unique region 114 to the center is longer than the distance from each part in the main region 113 to the center. Therefore, the electric field intensity is lower in the unique region 114 than in the main region 113. In the unique region 114, the electric field intensity is low, so that it takes a longer time for electrons generated by the incidence of radiation to flow into the first electrode 12. In addition, the electrons diffuse to a certain extent before flowing into the first electrode 12. Some of the diffused electrons may not be able to flow into the first electrode 12. The lower the electric field intensity, the more widely the electrons diffuse, and the proportion of electrons that cannot flow into the first electrode 12 increases. Therefore, the amount of charge acquired by the first electrode 12 by the incidence of radiation on the unique region 114 is reduced compared to the amount of charge acquired by the first electrode 12 by the incidence of radiation on the main region 113. The reduction in the amount of charge results in the radiation energy corresponding to the amount of charge being underdetected. In this embodiment, a process is performed to prevent the radiation energy from being underdetected.

[0051] Fig. 5 is a block diagram showing the functional configuration of the radiation detector 2 and the signal processing device 3 according to the first embodiment. In Fig. 5, the flow of signals is indicated by arrows. The radiation detection element 1 collects electrons in an amount corresponding to the energy of incident radiation at the first electrode 12, and outputs a current signal corresponding to the charge amount of the collected electrons from the first electrode 12. The preamplifier 21 converts the current signal output by the radiation detection element 1 into a voltage signal, and generates a step wave whose signal value rises in a single step shape when radiation is detected. The radiation detector 2 outputs a signal including the step wave generated by the preamplifier 21. The preamplifier 21 corresponds to a signal output unit.

[0052] FIG. 6 is a schematic graph showing an example of a signal including a step wave. The horizontal axis in the figure indicates time, and the vertical axis indicates a signal value. Each time an event occurs in which radiation is incident on the radiation detection element 1 and the radiation detection element 1 detects radiation, the radiation detector 2 outputs a step wave in which the signal value rises in one step. In response to one event, one step wave in which the signal value rises in one step is generated. When multiple events occur, a signal including multiple step waves is output. Each time an event occurs, the signal value rises. The height of the step in which the signal value rises is set to the wave height of the step wave. The wave height of the step wave corresponds to the amount of charge of electrons collected by the first electrode 12 by one event, and corresponds to the energy of the incident radiation. The radiation detection device 10 determines the energy of the radiation according to the wave height of the step wave.

[0053] FIG. 7 is a schematic graph showing an example of a step wave with a long duration. The horizontal axis in the figure indicates time, and the vertical axis indicates the signal value. FIG. 7 shows a step wave with a longer duration than the step wave shown in FIG. 6. If the time required for electrons generated by radiation to flow into the first electrode 12 is long, the time for the signal value to rise in steps becomes longer, and the time for the step wave to continue becomes longer. The lower the electric field intensity in the semiconductor part 11, the longer the time required for electrons generated by radiation to flow into the first electrode 12, and therefore the time for the step wave to continue becomes longer. Therefore, the time for which the step wave caused by the charge (electrons) generated in the unique region 114 by the incidence of radiation continues is longer than the time for which the step wave caused by the charge generated in the main region 113 continues. For example, the step wave shown in FIG. 6 is a step wave caused by the charge generated in the main region 113 by the incidence of radiation, and the step wave shown in FIG. 7 is a step wave caused by the charge generated in the unique region 114.

[0054] The signal output by the radiation detector 2 is input to the signal processing device 3. The signal processing device 3 executes a signal processing method. As shown in FIG. 5, the signal processing device 3 includes an A / D (analog / digital) conversion unit 31. The A / D conversion unit 31 receives a signal including a step wave from the radiation detector 2 and A / D converts the signal including the step wave. The A / D conversion unit 31 receives a continuous signal, samples the signal, and A / D converts the value obtained by sampling to generate discrete signal values. The signal output by the A / D conversion unit 31 is made up of a plurality of discrete signal values.

[0055] The A / D conversion unit 31 is connected to the trapezoid shaping unit 321 and the differentiation unit 331. The trapezoid shaping unit 321 and the differentiation unit 331 receive signals from the A / D conversion unit 31. A conversion unit that returns a signal so as to cancel out waveform distortion caused by signal delay, and a noise removal unit that removes noise from the signal may be connected between the A / D conversion unit 31 and the trapezoid shaping unit 321 and differentiation unit 331.

[0056] The trapezoid shaping unit 321 is configured using a trapezoid shaping filter. The trapezoid shaping unit 321 converts the step wave included in the signal into a trapezoid wave by shaping the waveform of the input signal using the trapezoid shaping filter. The height from a predetermined signal reference to the maximum value of the trapezoid wave is set as the wave height of the trapezoid wave. The wave height of the trapezoid wave converted from the step wave corresponds to the wave height of the step wave. The wave height measuring unit 322 is connected to the trapezoid shaping unit 321. The wave height measuring unit 322 receives the signal from the trapezoid shaping unit 321 and measures the wave height of the trapezoid wave included in the signal.

[0057] The differentiation unit 331 is configured using a differentiation circuit. The differentiation unit 331 may be configured using a processor that performs differentiation. The differentiation unit 331 differentiates the signal by calculating the difference between two adjacent signal values ​​included in the input signal. In this way, the differentiation unit 331 differentiates the step wave included in the signal.

[0058] The feature amount measuring unit 332 is connected to the differentiation unit 331. For example, the feature amount measuring unit 332 is configured using a processor that performs calculations. The feature amount measuring unit 332 measures a feature amount corresponding to the time that the step wave continues from the differentiation of the step wave. The feature amount measuring unit 332 calculates the time width of the step wave, the maximum value of the slope of the step wave, or the value of the second-order differential of the step wave as the feature amount of the step wave.

[0059] FIG. 8 is a schematic graph showing an example of a step wave and its differential waveform for explaining the characteristic amount. The upper part shows a signal consisting of a step wave, and the lower part shows a differential signal. The horizontal axis in the figure shows time, the vertical axis in the upper part shows the signal value, and the vertical axis in the lower part shows the differential value. The differential signal of the step wave is a signal whose signal value rises from a predetermined signal reference to a peak value and then falls to the signal reference. The signal reference is, for example, zero. The integral of the differential signal becomes the wave height of the step wave. As shown in FIG. 8, the length of time between two points at which the differential value of the step wave becomes a predetermined reference value is defined as the time width of the step wave. The reference value is determined in advance. The time width of the step wave corresponds to the time the step wave continues and is a quantity related to the shape of the step wave. The time width differs depending on the step wave and characterizes the step wave. If the time required for the charge generated by radiation to flow into the first electrode 12 is long, the time the step wave continues will be long and the time width will be long. Therefore, the step wave caused by the charge generated in the main region 113 by the incidence of radiation has a short time width, while the step wave caused by the charge generated in the unique region 114 has a long time width.

[0060] The longer the time width of the staircase wave, the smaller the change in the signal value per unit time, and therefore the smaller the slope of the staircase wave. Conversely, the shorter the time width of the staircase wave, the larger the slope of the staircase wave. In particular, the longer the time width of the staircase wave, the smaller the maximum value of the slope of the staircase wave, and the shorter the time width of the staircase wave, the larger the maximum value of the slope of the staircase wave. Therefore, the maximum value of the slope of the staircase wave corresponds to the time that the staircase wave continues, and is a quantity related to the shape of the staircase wave. Therefore, the maximum value of the slope of the staircase wave can be used as a feature quantity. In the staircase wave caused by the charge generated in the main region 113 by the incidence of radiation, the maximum value of the slope of the staircase wave is large, and in the staircase wave caused by the charge generated in the singular region 114, the maximum value of the slope of the staircase wave is small. The maximum value of the slope of the staircase wave can be obtained by measuring the maximum value of the differential of the staircase wave.

[0061] When the time required for the electric charge generated by radiation to flow into the first electrode 12 is long, the differential waveform of the staircase wave rises gradually, the time the staircase wave continues is long, and the slope of the rising edge of the differential waveform becomes small. The slope of the differential waveform becomes small. Conversely, when the time required for the electric charge to flow into the first electrode 12 is short, the differential waveform of the staircase wave rises steeply, the time the staircase wave continues is short, and the slope of the rising edge of the differential waveform becomes large. For this reason, the slope of the rising edge of the differential waveform of the staircase wave corresponds to the time the staircase wave continues, and is a quantity related to the shape of the staircase wave. The slope of the rising edge of the differential waveform of the staircase wave is the slope of the tangent to the differential waveform at the time when the differential value of the staircase wave becomes a predetermined reference value, and is the value of the second derivative of the staircase wave at this time. The reference value is a value for specifying a point in time of the rising edge of the differential waveform of the staircase wave. The reference value may be a constant value. The reference value may be the same as or different from the reference value for defining the time width of the staircase wave. Alternatively, the reference value may be a value that is a predetermined percentage of the maximum value of the differential value of the step wave, such as 1 / 10 of the maximum value of the differential value of the step wave. The value of the second-order differential of the step wave at the time when the differential value of the step wave becomes the predetermined reference value can be used as the feature amount. In the step wave caused by the charge generated in the main region 113 by the incidence of radiation, the value of the second-order differential at the time when the differential value becomes the reference value is large, and in the step wave caused by the charge generated in the singular region 114, the value of the second-order differential at the time when the differential value becomes the reference value is small.

[0062] The feature amount measuring unit 332 receives the signal from the differentiation unit 331 and calculates the feature amount of the step wave from the differential waveform of the step wave included in the signal. For example, the feature amount measuring unit 332 calculates the time width of the step wave as the feature amount by measuring the length of time between two points at which the differential value becomes a predetermined threshold value. For example, the feature amount measuring unit 332 calculates the maximum value of the slope of the step wave as the feature amount by measuring the maximum value of the differential value. For example, the feature amount measuring unit 332 calculates the value of the second-order differential of the step wave at the point at which the differential value of the step wave becomes a reference value as the feature amount.

[0063] The processing unit 34 is connected to the wave-height measuring unit 322 and the feature amount measuring unit 332. The processing unit 34 is configured using elements that perform calculations. For example, the processing unit 34 is configured using an FPGA (field-programmable gate array). The processing unit 34 receives the wave height from the wave-height measuring unit 322 and the feature amount of the staircase wave from the feature amount measuring unit 332. The processing unit 34 judges whether or not the staircase wave is caused by the charge generated in the unique region 114 based on the feature amount of the staircase wave calculated by the feature amount measuring unit 332. A judgment based on the feature amount is made based on the shape of the staircase wave.

[0064] For example, the processing unit 34 determines that the step wave is caused by the charge generated in the singular region 114 when the time width of the step wave is greater than a predetermined threshold, and determines that the step wave is not caused by the charge generated in the singular region 114 when the time width of the step wave is equal to or less than the predetermined threshold. The threshold is a boundary between the feature amount of the step wave caused by the charge generated in the main region 113 and the feature amount of the step wave caused by the charge generated in the singular region 114. The step wave not caused by the charge generated in the singular region 114 is a step wave caused by the charge generated in the main region 113. The processing unit 34 may determine that the step wave is caused by the charge generated in the singular region 114 when the time width of the step wave is equal to or greater than the threshold, and may determine that the step wave is not caused by the charge generated in the singular region 114 when the time width of the step wave is less than the threshold.

[0065] For example, when the maximum value of the slope of the step wave is less than a predetermined threshold, the processing unit 34 determines that the step wave is caused by charges generated in the unique region 114, and when the maximum value of the slope of the step wave is equal to or greater than the threshold, the processing unit 34 determines that the step wave is not caused by charges generated in the unique region 114. When the maximum value of the slope of the step wave is equal to or less than the threshold, the processing unit 34 may determine that the step wave is caused by charges generated in the unique region 114, and when the maximum value of the slope of the step wave is greater than the threshold, the processing unit 34 may determine that the step wave is not caused by charges generated in the unique region 114.

[0066] For example, if the value of the second-order differential of the step wave at the time when the differential value of the step wave becomes the reference value is less than a predetermined threshold, the processing unit 34 determines that the step wave is caused by the charge generated in the singular region 114, and if the maximum value of the second-order differential of the step wave at the time when the differential value of the step wave becomes the reference value is equal to or greater than the threshold, the processing unit 34 determines that the step wave is not caused by the charge generated in the singular region 114. If the value of the second-order differential of the step wave at the time when the differential value of the step wave becomes the reference value is equal to or less than the threshold, the processing unit 34 may determine that the step wave is caused by the charge generated in the singular region 114, and if the value of the second-order differential of the step wave at the time when the differential value of the step wave becomes the reference value is greater than the threshold, the processing unit 34 may determine that the step wave is not caused by the charge generated in the singular region 114.

[0067] The threshold of the characteristic quantity is determined in advance for each wave height. The greater the energy of the radiation incident on the semiconductor part 11, the more charges are generated and the easier it is for the electrons to spread over a wide area. Therefore, it takes longer for the electrons to flow into the first electrode 12, and the longer the time the step wave continues. Even if the step wave is caused by charges generated in the main region 113, the greater the energy of the incident radiation, the longer the time the step wave continues. The greater the energy of the radiation, the greater the wave height of the step wave and the longer the time the step wave continues. The threshold of the characteristic quantity is determined for each wave height so that the length of time of the step wave corresponding to the threshold increases monotonically with an increase in the wave height of the step wave.

[0068] For example, the threshold value of the time width of the step wave is determined for each wave height so as to monotonically increase with increasing wave height of the step wave. For example, the threshold value of the maximum value of the slope of the step wave is determined for each wave height so as to monotonically decrease with increasing wave height of the step wave. For example, the threshold value for the value of the second derivative of the step wave at the time when the derivative value of the step wave becomes the reference value is determined for each wave height so as to monotonically decrease with increasing wave height of the step wave. Since the threshold value is determined in this manner, when the energy of the radiation is large, the step wave caused by the charge generated in the main region 113 is not erroneously determined to be the step wave caused by the charge generated in the unique region 114. Therefore, it is accurately determined whether the step wave is caused by the charge generated in the unique region 114 or not.

[0069] The processing unit 34 stores in advance a threshold value of a predetermined feature amount associated with each of a plurality of wave heights. The processing unit 34 reads out the threshold value associated with the wave height measured by the wave-height measuring unit 322, and compares the read-out threshold value with the feature amount of the step wave calculated by the feature amount measuring unit 332 to determine whether the step wave is caused by the electric charge generated in the unique region 114.

[0070] The processing unit 34 may have a configuration in which the threshold value of the feature is constant, and when determining whether or not the step wave is caused by the charge generated in the unique region 114, the processing unit 34 corrects the feature value in accordance with the wave height of the step wave. In this configuration, the processing unit 34 corrects the feature value so that the length of time of the step wave corresponding to the threshold value monotonically decreases with an increase in the wave height of the step wave. For example, the processing unit 34 stores a constant as the threshold value of the time width of the step wave, and when determining whether or not the step wave is caused by the charge generated in the unique region 114, the processing unit 34 corrects the feature value so that the length of time of the step wave corresponding to the threshold value monotonically decreases with an increase in the wave height of the step wave. decrease The processing unit 34 compares the corrected time width with a threshold value to determine whether the step wave is caused by charges generated in the unique region 114.

[0071] For example, the processing unit 34 stores a constant as a threshold value for the maximum value of the slope of the staircase wave, and when determining whether or not the staircase wave is caused by the charge generated in the singular region 114, corrects the maximum value of the slope of the staircase wave so that it increases monotonically with respect to an increase in the wave height of the staircase wave. The processing unit 34 compares the threshold value with the maximum value of the slope after the correction to determine whether or not the staircase wave is caused by the charge generated in the singular region 114. For example, the processing unit 34 stores a constant as a threshold value for the value of the second-order differential of the staircase wave at the time when the differential value of the staircase wave becomes a reference value, and corrects the value of the second-order differential of the staircase wave at the time when the differential value of the staircase wave becomes a reference value so that it increases monotonically with respect to an increase in the wave height of the staircase wave. The processing unit 34 compares the threshold value with the corrected value of the second-order differential to determine whether or not the staircase wave is caused by the charge generated in the singular region 114.

[0072] In this way, even in the case where the threshold value is fixed and the feature amount is corrected according to the wave height of the step wave, when the radiation energy is large, the step wave caused by the charge generated in the main region 113 is not erroneously determined to be the step wave caused by the charge generated in the unique region 114. Therefore, it is accurately determined whether or not the step wave is caused by the charge generated in the unique region 114.

[0073] The counting unit 35 is connected to the processing unit 34. The counting unit 35 counts the step waves for each wave height. For example, the counting unit 35 is a multi-channel analyzer. The counting unit 35 may be configured to count pulse waves for all wave heights, or may be configured to count pulse waves only for a specific wave height.

[0074] When the staircase wave is not caused by the charge generated in the unique region 114, that is, when the staircase wave is caused by the charge generated in the main region 113, the processing unit 34 inputs an instruction to the counting unit 35 to count +1 for the wave height measured by the wave-height measuring unit 322. The counting unit 35 counts the wave height measured by the wave-height measuring unit 322 according to the input instruction. In this way, the counting unit 35 counts the staircase wave not caused by the charge generated in the unique region 114. When the staircase wave is caused by the charge generated in the unique region 114, the processing unit 34 does not input an instruction for counting to the counting unit 35. As a result, the counting unit 35 does not count the staircase wave caused by the charge generated in the unique region 114.

[0075] The signal processing device 3 outputs data indicating the relationship between the wave height of the step wave and the count number counted by the counting unit 35. The count number corresponds to the number of times that the radiation detector 2 detects radiation having energy corresponding to the wave height of the step wave.

[0076] FIG. 9 is a block diagram showing an example of the internal configuration of the analysis device 4. The analysis device 4 is a computer such as a personal computer. The analysis device 4 includes a calculation unit 41, a memory 42, a drive unit 43, a storage unit 44, and an operation unit 45. The analysis device 4 is also connected to a display unit 53 and a signal processing device 3. The calculation unit 41 is configured using, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a multi-core CPU. The calculation unit 41 may be configured using a quantum computer. The memory 42 stores temporary data generated in association with the calculation. The memory 42 is, for example, a RAM (Random Access Memory). The drive unit 43 reads information from a recording medium 40 such as an optical disk or a portable memory.

[0077] The storage unit 44 is non-volatile, and is, for example, a hard disk or a non-volatile semiconductor memory. The operation unit 45 receives input of information such as text by receiving operations from a user. The operation unit 45 is, for example, a touch panel, a keyboard, or a pointing device.

[0078] The calculation unit 41 causes the drive unit 43 to read the computer program 441 recorded on the recording medium 40, and stores the read computer program 441 in the storage unit 44. The calculation unit 41 executes processing required for the analysis device 4 according to the computer program 441. The computer program 441 may be downloaded from outside the analysis device 4. Alternatively, the computer program 441 may be stored in advance in the storage unit 44. In these cases, the analysis device 4 may not have the drive unit 43. The analysis device 4 may be composed of multiple computers. Alternatively, the control unit 52 and the analysis device 4 may be composed of the same computer.

[0079] The analysis device 4 receives the data output by the signal processing device 3. The analysis device 4 performs processing to generate a spectrum of the radiation detected by the radiation detector 2 from the relationship between the wave height of the step wave and the count number. The spectrum represents the relationship between the energy of the radiation corresponding to the wave height and the count number. The calculation unit 41 executes necessary processing according to the computer program 441. The analysis device 4 may further perform further processing such as elemental analysis of the radiation source based on the generated spectrum of the radiation. For example, the radiation detector 2 detects fluorescent X-rays, and the analysis device 4 performs qualitative analysis or quantitative analysis of elements contained in the sample based on the spectrum of the fluorescent X-rays. The display unit 53 displays the spectrum generated by the analysis device 4 and the analysis results by the analysis device 4. The signal processing device 3 may also have a function of generating a spectrum of the radiation.

[0080] The flow of processing executed by the radiation detection device 10 will be described. FIG. 10 is a flowchart showing the procedure of processing executed by the signal processing device 3 according to the first embodiment. Hereinafter, step is abbreviated as S. When radiation is incident on the radiation detection element 1, the radiation detector 2 generates a step wave having a wave height according to the energy of the radiation, and outputs a signal including the step wave. The signal processing device 3 receives the signal including the step wave from the radiation detector 2 (S11). The A / D conversion unit 31 A / D converts the input signal (S12).

[0081] The A / D converted signal is subjected to pulse height measurement and feature measurement (S13). In S13, the trapezoid shaping unit 321 converts the waveform of the A / D converted signal into a trapezoidal wave, and the pulse height measurement unit 322 measures the pulse height of the trapezoidal wave to measure the pulse height of the step wave contained in the signal. Furthermore, the differentiation unit 331 differentiates the A / D converted signal, and the feature measurement unit 332 measures the feature amount of the step wave contained in the signal. For example, the feature measurement unit 332 calculates, as the feature amount of the step wave, the time width of the step wave, the maximum value of the slope of the step wave, or the value of the second-order differential of the step wave at the point when the differential value of the step wave becomes a reference value.

[0082] The processing unit 34 judges whether the staircase wave is caused by the charge generated in the unique region 114 based on the feature amount measured by the feature amount measuring unit 332 (S14). If the staircase wave is not caused by the charge generated in the unique region 114 (S14: NO), the processing unit 34 inputs an instruction to the counting unit 35 to count +1, and the counting unit 35 counts +1 for the wave height measured by the wave height measuring unit 322 (S15). In S15, the counting unit 35 adds +1 to the count number up to that point. By the processes of S14 and S15, the staircase wave caused by the charge generated in the main region 113 is counted. After the process of S15 is completed, the signal processing device 3 ends the process. If the staircase wave is caused by the charge generated in the unique region 114 (S14: YES), the processing unit 34 ends the process without issuing an instruction to count. That is, if the staircase wave is caused by the charge generated in the unique region 114, the signal processing device 3 does not count the staircase wave.

[0083] The signal processing device 3 repeatedly executes the processes of S11 to S15. The amount of charge acquired by the first electrode 12 due to the incidence of radiation on the unique region 114 is smaller than the amount of charge acquired by the first electrode 12 due to the incidence of radiation on the main region 113. For this reason, when the step wave is caused by the charge generated in the unique region 114, the energy corresponding to the wave height may be smaller than the energy of the radiation incident on the unique region 114. By not counting the step wave when the step wave is caused by the charge generated in the unique region 114, it is possible to prevent the energy of the radiation incident on the radiation detection element 1 from being underdetected.

[0084] The signal processing device 3 outputs data indicating the relationship between the wave height of the step wave and the number of counts counted by the counting unit 35. The analysis device 4 receives the data output by the signal processing device 3. The calculation unit 41 of the analysis device 4 generates a spectrum of the radiation detected by the radiation detector 2 based on the input data. The analysis device 4 corresponds to a spectrum generation unit. The calculation unit 41 displays the spectrum of the radiation on the display unit 53. The count number on which the spectrum is based does not include the number of step waves caused by the charges generated in the unique region 114, but includes the number of step waves caused by the charges generated in the main region 113. The spectrum does not include detection results of radiation in which the energy is underdetected, but includes detection results of radiation in which the energy is detected almost accurately. Therefore, deterioration of the accuracy of radiation detection is sufficiently suppressed.

[0085] In this embodiment, the radiation detector 2 does not include a collimator that blocks a portion of the radiation incident on the radiation detection element 1. That is, in this embodiment, it is possible to suppress a decrease in the accuracy of radiation detection without using a collimator. Since the radiation detector 2 does not include a collimator, a system peak caused by the collimator does not occur in the radiation spectrum, and the accuracy of radiation detection improves. Since the collimator does not block the radiation incident on the main region 113 with high electric field intensity, the sensitivity of radiation detection improves. Furthermore, by not providing a collimator, the cost of the radiation detector 2 is reduced.

[0086] <Embodiment 2> In the second embodiment, radiation is counted by an analysis device 4. The configuration of the radiation detection device 10 other than the signal processing device 3 is the same as in the first embodiment. FIG. 11 is a block diagram showing the functional configuration of a radiation detector 2 and a signal processing device 3 according to the second embodiment. The radiation detector 2 is the same as in the first embodiment. The A / D conversion unit 31, trapezoid shaping unit 321, pulse-height measurement unit 322, differentiation unit 331, and feature measurement unit 332 provided in the signal processing device 3 are the same as in the first embodiment.

[0087] The signal processing device 3 does not include a counting unit. The processing unit 34 receives the wave height from the wave-height measuring unit 322 and the feature amount of the staircase wave from the feature amount measuring unit 332. The processing unit 34 determines whether or not the staircase wave is caused by charges generated in the unique region 114, based on the feature amount of the staircase wave calculated by the feature amount measuring unit 332.

[0088] When the staircase wave is not caused by charges generated in the unique region 114, i.e., when the staircase wave is caused by charges generated in the main region 113, the processing unit 34 inputs information including the wave height measured by the wave height measurement unit 322 to the analysis device 4. The analysis device 4 counts the staircase waves by wave height according to the information input from the processing unit 34. When the staircase wave is caused by charges generated in the unique region 114, the processing unit 34 does not input information to the analysis device 4. As a result, the analysis device 4 does not count the staircase wave caused by charges generated in the unique region 114.

[0089] 12 is a flowchart showing the procedure of the process executed by the signal processing device 3 and the analysis device 4 according to the second embodiment. The signal processing device 3 receives a signal including a step wave from the radiation detector 2 (S21), and the A / D conversion unit 31 performs A / D conversion on the input signal (S22). The A / D converted signal is subjected to pulse height measurement and feature amount measurement (S23). In S23, the trapezoid shaping unit 321 converts the signal waveform into a trapezoid wave, and the pulse height measurement unit 322 measures the pulse height of the step wave. In addition, the differentiation unit 331 differentiates the signal, and the feature amount measurement unit 332 calculates the feature amount of the step wave. For example, the feature amount measurement unit 332 calculates, as the feature amount of the step wave, the time width of the step wave, the maximum value of the slope of the step wave, or the value of the second order differential of the step wave at the time when the differential value of the step wave becomes a reference value.

[0090] The processing unit 34 judges whether or not the staircase wave is caused by the charge generated in the unique region 114 based on the feature amount measured by the feature amount measuring unit 332 (S24). If the staircase wave is not caused by the charge generated in the unique region 114 (S24: NO), the processing unit 34 outputs information including the wave height measured by the wave height measuring unit 322 and inputs it to the analysis device 4 (S25). The analysis device 4 accepts the input information and stores it in the memory unit 44. The analysis device 4 stores the count number of the staircase wave in association with the wave height in the memory unit 44.

[0091] When information including the wave height is input, the analysis device 4 counts the step waves according to the wave height included in the information (S26). In S26, the calculation unit 41 adds +1 to the count number stored in association with the wave height included in the input information. The number stored in the memory unit 44 by the analysis device 4 is the number of step waves counted by wave height. By the processes of S24 to S26, the step waves caused by the charge generated in the main region 113 are counted by wave height. After the process of S26 is completed, the signal processing device 3 and the analysis device 4 end the process.

[0092] If the step wave is caused by charges generated in the unique region 114 (S24: YES), the processing unit 34 ends the process as is. That is, if the step wave is caused by charges generated in the unique region 114, the signal processing device 3 does not input information including the wave height of the step wave to the analysis device 4, and the analysis device 4 does not count the step wave. The signal processing device 3 and the analysis device 4 repeatedly execute the processes of S21 to S26. Also in the second embodiment, by not counting the step wave when the step wave is caused by charges generated in the unique region 114, it is possible to prevent the energy of the radiation incident on the radiation detection element 1 from being underdetected.

[0093] The calculation unit 41 of the analysis device 4 generates a spectrum of the radiation detected by the radiation detector 2 based on the count numbers for each pulse height stored in the memory unit 44. The calculation unit 41 causes the display unit 53 to display the spectrum of the radiation. In the second embodiment as well, the spectrum does not include detection results of radiation in which the energy is detected too low, but includes detection results of radiation in which the energy is detected almost accurately. Therefore, a decrease in the accuracy of radiation detection is sufficiently suppressed. The analysis device 4 may be configured to perform part or all of the processing in the processing unit 34.

[0094] In the second embodiment as well, a collimator is not used, and thus a decrease in the accuracy of radiation detection is suppressed. As in the first embodiment, the radiation detector 2 does not include a collimator, and thus the accuracy of radiation detection is improved, and the sensitivity of radiation detection is improved. In addition, the cost of the radiation detector 2 is reduced.

[0095] In the first and second embodiments, the trapezoidal wave generated by the trapezoid shaping unit 321 is used to calculate the wave height of the step wave, but the signal processing device 3 may calculate the wave height of the step wave by integrating the differentiated waveform generated by the differentiation unit 331. In the first and second embodiments, the function of the signal processing device 3 is realized by hardware, but the signal processing device 3 may be realized by software in part or in whole.

[0096] In the first and second embodiments, the determination is made based on the feature amount of the staircase wave, but the signal processing device 3 may be configured to make a determination based on the shape of the staircase wave using a learning model. For example, the signal processing device 3 is provided with a learning model that outputs a determination result as to whether or not the staircase wave is caused by the charge generated in the unique region 114 when a waveform of the staircase wave or a differential waveform of the staircase wave is input. The learning model is previously trained using training data including a waveform or a differential waveform of the staircase wave caused by the charge generated in the main region 113 and a waveform or a differential waveform of the staircase wave caused by the charge generated in the unique region 114. In this embodiment, the signal processing device 3 inputs the waveform or differential waveform of the staircase wave to the learning model and obtains the determination result output from the learning model to determine whether or not the staircase wave is caused by the charge generated in the unique region 114.

[0097] In the first and second embodiments, the radiation detector 2 does not include a collimator, but the radiation detector 2 may include a collimator. The collimator is disposed between the radiation detection element 1 and the window 24. In a form in which the radiation detector 2 includes a collimator, the collimator blocks radiation attempting to enter the unique region 114. Even when radiation passes through the collimator and enters the unique region 114, the step wave caused by the charge generated in the unique region 114 is not counted, thereby preventing the radiation energy from being underdetected. Therefore, in addition to the effect of the collimator suppressing the deterioration of the accuracy of radiation detection, the deterioration of the accuracy of radiation detection is more effectively suppressed.

[0098] In the first and second embodiments, the unique region 114 is disposed around the main region 113, but the unique region 114 may have other shapes. The arrangement of the unique region 114 is determined by the arrangement of the electrodes, such as the first electrode 12, the second electrode 13, and the curved electrode 14. Depending on the arrangement of the electrodes, the shape of the unique region 114 may be different from the shapes shown in the first and second embodiments. Even if the shape of the unique region 114 is different from the shapes shown in the first and second embodiments, the decrease in the accuracy of radiation detection is sufficiently suppressed.

[0099] In the first and second embodiments, the semiconductor constituting the radiation detection element 1 is Si, but the radiation detection element 1 may be configured with a semiconductor other than Si. In the first and second embodiments, the semiconductor portion 11 is configured with an n-type semiconductor, and the second electrode 13 is configured with a p-type semiconductor, but the radiation detection element 1 may be configured with a semiconductor portion 11 is configured with a p-type semiconductor, and the second electrode 13 is configured with an n-type semiconductor. In this configuration, holes are collected in the first electrode 12 as the electric charge. In the first and second embodiments, the radiation detection element 1 is configured with a silicon drift type radiation detection element, but the radiation detection element 1 may be an element other than a silicon drift type radiation detection element as long as it is an element made of a semiconductor. For this reason, the radiation detector 2 may be a radiation detector other than an SDD.

[0100] In the first and second embodiments, radiation is irradiated to the sample 62 and radiation generated from the sample 62 is detected, but the radiation detection device 10 may be configured to detect radiation that has passed through the sample 62 or that has been reflected by the sample 62. The radiation detection device 10 may be configured to scan the sample 62 with radiation by changing the direction of the radiation. The radiation detection device 10 may be configured to irradiate a moving sample with radiation. The radiation detection device 10 may be configured not to include the irradiation unit 54, the sample stage 61, or the display unit 53.

[0101] The present invention is not limited to the contents of the above-described embodiment, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention. [Explanation of symbols]

[0102] 10 Radiation detection equipment 1 Radiation detection element 11 Semiconductor Department 12 1st electrode 13 Second electrode 2. Radiation detector 21 Preamplifier 3. Signal Processing Device 332 Feature Measurement Unit 34 Processing section 35 Counting section 4 Analyzer 40 Recording media 441 Computer Programs

Claims

1. A method for processing a signal output by a signal output unit using a semiconductor unit, a single first electrode provided on the semiconductor unit and collecting charges generated in the semiconductor unit by radiation incident on the semiconductor unit, a second electrode provided on the semiconductor unit and generating an electric field in the semiconductor unit by application of a voltage to cause the charges to concentrate on the first electrode, and a signal output unit that outputs a signal including a step wave having a wave height according to an amount of charges collected by the first electrode, the method comprising: the semiconductor portion has a unique region in which the intensity of the electric field is lower than that of other regions, performing a determination process for determining whether or not the step wave is caused by charges generated in the unique region based on the feature amount of the step wave; When the step wave is not caused by the charge generated in the specific region, the step wave is counted by wave height; When the step wave is caused by an electric charge generated in the specific region, the step wave is not counted, the feature value is a time width of the step wave, In the determination process, when the feature amount is larger than a threshold value that is predetermined for each wave height so as to monotonically increase with an increase in the wave height of the step wave, it is determined that the step wave is caused by charges generated in the unique region, or the feature amount is corrected according to the wave height of the step wave so that the corrected feature amount monotonically decreases with an increase in the wave height of the step wave, and when the corrected feature amount is larger than a predetermined threshold value, it is determined that the step wave is caused by charges generated in the unique region.

23. A signal processing method comprising:

2. A method for processing a signal output by a signal output unit using a semiconductor unit, a single first electrode provided on the semiconductor unit and collecting charges generated in the semiconductor unit by radiation incident on the semiconductor unit, a second electrode provided on the semiconductor unit and generating an electric field in the semiconductor unit by application of a voltage to cause the charges to concentrate on the first electrode, and a signal output unit that outputs a signal including a step wave having a wave height according to an amount of charges collected by the first electrode, the method comprising: the semiconductor portion has a unique region in which the intensity of the electric field is lower than that of other regions, performing a determination process for determining whether or not the step wave is caused by charges generated in the unique region based on the feature amount of the step wave; When the step wave is not caused by the charge generated in the specific region, the step wave is counted by wave height; When the step wave is caused by an electric charge generated in the specific region, the step wave is not counted, the characteristic amount is a maximum value of a slope of the step wave, or a value of a second-order differential of the step wave at a point in time when a differential value of the step wave becomes a predetermined reference value, In the determination process, when the feature amount is less than a threshold value that is predetermined for each wave height so that the feature amount monotonically decreases with an increase in the wave height of the step wave, it is determined that the step wave is caused by charges generated in the unique region, or the feature amount is corrected according to the wave height of the step wave so that the corrected feature amount monotonically increases with an increase in the wave height of the step wave, and when the corrected feature amount is less than a predetermined threshold, it is determined that the step wave is caused by charges generated in the unique region.

23. A signal processing method comprising:

3. A radiation detection device comprising: a radiation detection element; a signal output unit that outputs a signal corresponding to radiation incident on the radiation detection element; and a signal processing device that processes the signal output by the signal output unit, The radiation detection element includes a semiconductor portion, a single first electrode provided in the semiconductor portion for collecting charges generated in the semiconductor portion by radiation incident on the semiconductor portion, and a second electrode provided in the semiconductor portion for generating an electric field in the semiconductor portion by application of a voltage thereto for concentrating the charges at the first electrode, the signal output unit outputs a signal including a step wave having a wave height corresponding to an amount of charge collected by the first electrode; the semiconductor portion has a unique region in which the intensity of the electric field is lower than that of other regions, The signal processing device performs a determination process to determine whether or not the step wave is caused by charges generated in the unique region based on the feature amount of the step wave, and counts the step wave by wave height when the step wave is not caused by charges generated in the unique region, and does not count the step wave when the step wave is caused by charges generated in the unique region, the feature value is a time width of the step wave, In the determination process, the signal processing device determines that the step wave is caused by charges generated in the unique region when the feature amount is larger than a threshold value that is predetermined for each wave height so that the feature amount increases monotonically with an increase in the wave height of the step wave, or corrects the feature amount according to the wave height of the step wave so that the corrected feature amount decreases monotonically with an increase in the wave height of the step wave, and determines that the step wave is caused by charges generated in the unique region when the corrected feature amount is larger than a predetermined threshold value. A radiation detection device comprising:

4. A radiation detection device comprising: a radiation detection element; a signal output unit that outputs a signal corresponding to radiation incident on the radiation detection element; and a signal processing device that processes the signal output by the signal output unit, The radiation detection element includes a semiconductor portion, a single first electrode provided in the semiconductor portion for collecting charges generated in the semiconductor portion by radiation incident on the semiconductor portion, and a second electrode provided in the semiconductor portion for generating an electric field in the semiconductor portion by application of a voltage thereto for concentrating the charges at the first electrode, the signal output unit outputs a signal including a step wave having a wave height corresponding to an amount of charge collected by the first electrode; the semiconductor portion has a unique region in which the intensity of the electric field is lower than that of other regions, The signal processing device performs a determination process to determine whether or not the step wave is caused by charges generated in the unique region based on the feature amount of the step wave, and counts the step wave by wave height when the step wave is not caused by charges generated in the unique region, and does not count the step wave when the step wave is caused by charges generated in the unique region, the characteristic amount is a maximum value of a slope of the step wave, or a value of a second-order differential of the step wave at a point in time when a differential value of the step wave becomes a predetermined reference value, In the determination process, the signal processing device determines that the step wave is caused by charges generated in the unique region when the feature amount is less than a threshold value that is predetermined for each wave height so that the feature amount monotonically decreases with an increase in the wave height of the step wave, or corrects the feature amount according to the wave height of the step wave so that the corrected feature amount monotonically increases with an increase in the wave height of the step wave, and determines that the step wave is caused by charges generated in the unique region when the corrected feature amount is less than a predetermined threshold value. A radiation detection device comprising:

5. No collimator is provided to block a portion of the radiation incident on the semiconductor portion.

5. The radiation detection device according to claim 3, wherein the radiation detection device is a radiation detector.

6. an irradiation unit that irradiates radiation onto the sample; a spectrum generating unit that generates a spectrum of radiation representing a relationship between the number of counts counted by the signal processing device and a pulse height; a display unit that displays the spectrum generated by the spectrum generation unit; 6. The radiation detection device according to claim 3, further comprising:

7. A computer program for causing a computer to process signals outputted using a semiconductor section, a single first electrode provided on the semiconductor section and configured to collect charges generated within the semiconductor section by radiation incident on the semiconductor section, a second electrode provided on the semiconductor section and configured to generate an electric field within the semiconductor section by application of a voltage to cause the charges to concentrate on the first electrode, and a signal output section that outputs a signal including a step wave having a wave height according to an amount of charges collected by the first electrode, performing a determination process for determining whether or not the step wave is caused by charges generated in a unique region in the semiconductor portion where the intensity of the electric field is lower than that in other regions, based on the feature amount of the step wave; When the step wave is not caused by the charge generated in the specific region, the step wave is counted by wave height; When the step wave is caused by an electric charge generated in the specific region, the step wave is not counted according to wave height, generating a spectrum of radiation representing a relationship between the number of counts of the step wave and the wave height; the feature value is a time width of the step wave, In the determination process, when the feature amount is larger than a threshold value that is predetermined for each wave height so as to monotonically increase with an increase in the wave height of the step wave, it is determined that the step wave is caused by charges generated in the unique region, or the feature amount is corrected according to the wave height of the step wave so that the corrected feature amount monotonically decreases with an increase in the wave height of the step wave, and when the corrected feature amount is larger than a predetermined threshold value, it is determined that the step wave is caused by charges generated in the unique region. A computer program that causes a computer to execute a process.

8. A computer program for causing a computer to process signals outputted using a semiconductor section, a single first electrode provided on the semiconductor section and configured to collect charges generated within the semiconductor section by radiation incident on the semiconductor section, a second electrode provided on the semiconductor section and configured to generate an electric field within the semiconductor section by application of a voltage to cause the charges to concentrate on the first electrode, and a signal output section that outputs a signal including a step wave having a wave height according to an amount of charges collected by the first electrode, performing a determination process for determining whether or not the step wave is caused by charges generated in a unique region in the semiconductor portion where the intensity of the electric field is lower than that in other regions, based on the feature amount of the step wave; When the step wave is not caused by the charge generated in the specific region, the step wave is counted by wave height; When the step wave is caused by an electric charge generated in the specific region, the step wave is not counted according to wave height, generating a spectrum of radiation representing a relationship between the number of counts of the step wave and the wave height; the characteristic amount is a maximum value of a slope of the step wave, or a value of a second-order differential of the step wave at a point in time when a differential value of the step wave becomes a predetermined reference value, In the determination process, when the feature amount is less than a threshold value that is predetermined for each wave height so that the feature amount monotonically decreases with an increase in the wave height of the step wave, it is determined that the step wave is caused by charges generated in the unique region, or the feature amount is corrected according to the wave height of the step wave so that the corrected feature amount monotonically increases with an increase in the wave height of the step wave, and when the corrected feature amount is less than a predetermined threshold, it is determined that the step wave is caused by charges generated in the unique region. A computer program that causes a computer to execute a process.

Images