JP7624899B2 - Signal processing method, radiation detection device, and computer program - Google Patents

Description

The present invention relates to a signal processing method, a radiation detection device, and a computer program for processing signals generated by radiation detection.

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 holes move according to the electric field, the electrons are collected at the first electrode, and a signal corresponding to the charge 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 and second electrodes.

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 a 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, if 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.

Conventionally, radiation detectors are equipped with a collimator. The collimator blocks radiation that is about to enter a portion of the semiconductor section where the electric field strength is low, and allows radiation that is about to enter a portion of the semiconductor section where the electric field strength is high to pass through. The collimator prevents radiation from entering a portion of the semiconductor section where the electric field strength is low, suppressing a decrease in the accuracy of radiation detection.

Patent No. 6159133

High-energy radiation can pass through the 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 were insufficient in preventing the reduction in accuracy of radiation detection.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a signal processing method, a radiation detection device, and a computer program that can sufficiently suppress deterioration in the accuracy of radiation detection.

The signal processing method according to the present invention uses a semiconductor part, a single first electrode provided in the semiconductor part for collecting charges generated in the semiconductor part by radiation incident on the semiconductor part, a second electrode provided in the semiconductor part for generating an electric field for concentrating the charges in the semiconductor part on the first electrode by applying a voltage, and a signal output part for outputting a signal including a step wave having a wave height according to the amount of charge collected by the first electrode, and processes a signal output by the signal output part, the semiconductor part has 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 the charge generated in the singular region, and if the step wave is not caused by the charge generated in the singular region, the step wave is counted by wave height, and if the step wave is caused by the charge generated in the singular region, the step wave is not counted.

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 concentrates the charges at the first electrode, and a signal including a step wave having a wave height according to the amount of the charge 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. Based on the shape of the step wave, it is determined whether or not the step wave is caused by the charge generated in the peculiar region. If the step wave is not caused by the charge generated in the peculiar region, the step wave is counted according to its wave height, and if the step wave is caused by the charge generated in the peculiar region, the step wave is not counted. In the peculiar region, the intensity of the electric field is low, so the charge generated by the radiation is 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 radiation energy is underdetected by the reduction in the amount of charge. By not counting the step wave caused by the charge generated in the peculiar region, the radiation energy is prevented from being underdetected.

The signal processing method according to the present invention is characterized in that, when the length of time corresponding to the feature is long, the step wave is determined to be caused by charges generated in the anomalous region, with a predetermined threshold as a boundary, and the threshold is set for each wave height such that the length of time corresponding to the threshold increases monotonically with an increase in the wave height of the step wave.

In one embodiment of the present invention, based on a feature value corresponding to the length of time the step wave continues, a predetermined threshold is set as a boundary, and if the length of time corresponding to the feature value is long, it is determined that the step wave is caused by charges generated in the anomalous region. The threshold value is set 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 area, and the longer the step wave will continue. By setting the threshold value as described above, it is possible to accurately determine whether the step wave is caused by charges generated in the anomalous region.

The signal processing method according to the present invention is characterized in that it measures a feature value corresponding to the length of time that the step wave continues, corrects the feature value according to the wave height of the step wave so that the length of time corresponding to the corrected feature value monotonically decreases as the wave height of the step wave increases, and determines that the step wave is caused by charges generated in the singular region based on the corrected feature value, with a predetermined threshold value as the boundary.

In one embodiment of the present invention, a feature value corresponding to the length of time that the step wave continues is measured, the feature value is corrected according to the wave height of the step wave, and if the length of time corresponding to the corrected feature value is long with a certain threshold as a boundary, it is determined that the step wave is caused by charges generated in the anomalous region. The feature value is corrected so that the length of time corresponding to 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 time that the step wave continues, so by correcting the feature value as described above, it is possible to accurately determine whether the step wave is caused by charges generated in the anomalous region.

The signal processing method according to the present invention is characterized in that the feature is the time width of the step wave.

In one embodiment of the present invention, the characteristic quantity of the staircase wave is the time width of the staircase wave. The time width corresponds to the length of time that the staircase wave continues. If the time width is long, it is determined that the staircase wave is caused by charges generated in the anomalous region.

The signal processing method according to the present invention is characterized in that the feature is the maximum value of the slope of the step wave.

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 that 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 singular region.

In the signal processing method according to the present invention, the feature value is the value of the second derivative of the step wave at the time when the derivative value of the step wave becomes a predetermined reference value.

In one embodiment of the present invention, the characteristic amount of the staircase wave is the value of the second derivative at the time when the derivative of the staircase wave becomes a predetermined reference value. If the time required for the charge generated by radiation to flow into the first electrode is long, the derivative waveform of the staircase wave rises gradually and the slope of the rise of the derivative waveform becomes small. Conversely, if the time required for the charge to flow into the first electrode is short, the derivative waveform of the staircase wave rises steeply and the slope of the rise of the derivative waveform becomes large. Therefore, the slope of the rise of the derivative waveform of the staircase wave corresponds to the time the staircase wave continues. The slope of the rise of the derivative waveform is the value of the second derivative at the time when the derivative of the staircase wave becomes a predetermined reference value. If the value of the second derivative at the time when the derivative of the staircase wave becomes the reference value is small, it is determined that the staircase wave is caused by the charge generated in the singular region.

The 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. The radiation detection element includes a semiconductor portion, a single first electrode that is provided on the semiconductor portion and collects charges generated in the semiconductor portion due to radiation incident on the semiconductor portion, and a second electrode that is provided on the semiconductor portion and generates an electric field in the semiconductor portion to concentrate the charges on the first electrode by applying a voltage. The signal output unit outputs a signal including a step wave having a wave height corresponding to the 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. The signal processing device determines whether the step wave is caused by charges generated in the singular region based on the shape of the step wave, and counts the step wave by wave height when the step wave is not caused by charges generated in the singular region, and does not count the step wave when the step wave is caused by charges generated in the singular region.

In one embodiment of the present invention, the 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.

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

In one embodiment of the present invention, the radiation detection device does not include a collimator. Even without using a collimator, under-detection of radiation energy is prevented, and a decrease in the accuracy of radiation detection is suppressed.

The radiation detection device according to the present invention is characterized by further comprising an irradiation unit that irradiates a sample with radiation, a spectrum generation unit that generates a spectrum of radiation that represents the relationship between the number of counts counted by the signal processing device and the pulse height, and a display unit that displays the spectrum generated by the spectrum generation unit.

In one embodiment of the present invention, the radiation detection device generates a spectrum of radiation. A spectrum of radiation whose energy is detected almost accurately is generated and displayed on the display unit.

The 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 in the semiconductor section due to radiation incident on the semiconductor section, a second electrode provided in the semiconductor section that generates an electric field in the semiconductor section to concentrate the charges on the first electrode by applying a voltage, and a signal output section that outputs a signal including a step wave having a height according to the amount of charge collected by the first electrode, and is characterized in that the computer executes a process of counting the step wave by 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 height when it is determined that the step wave is caused by charges generated in the unique region, and generating a spectrum of radiation that represents the relationship between the number of counts of the step wave and the height.

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

The present invention has the excellent effect of preventing the radiation energy from being detected as being too low, thereby sufficiently suppressing the deterioration of the accuracy of radiation detection.

2 is a block diagram showing an example of a functional configuration of the radiation detection apparatus; 1 is a schematic cross-sectional view showing an example of a radiation detection element. FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a radiation detector. 4 is a graph showing a schematic diagram of the electric field intensity inside a semiconductor portion. 1 is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to a first embodiment. 1 is a schematic graph showing an example of a signal including a step wave. 1 is a schematic graph showing an example of a step wave having a long duration. 11 is a schematic graph showing an example of a step wave and its differential waveform for explaining a feature amount. FIG. 2 is a block diagram showing an example of the internal configuration of an analysis device. 4 is a flowchart showing a procedure of a process executed by the signal processing device according to the first embodiment. FIG. 11 is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to a second embodiment. 10 is a flowchart showing a procedure of a process executed by a signal processing device and an analysis device according to a second embodiment.

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, 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.

The radiation detector 2 includes a radiation detection element 1 and a preamplifier 21. The radiation detector 2 is connected to 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. The signal processing device 3 is connected to an analysis device 4. 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. The analysis device 4 is connected to a display unit 53 such as a liquid crystal display or an EL display (Electroluminescent Display). The control unit 52 may be configured to receive operations from a user and control each part of the radiation detection device 10 in response to the received operations.

Figure 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 has a disk-shaped semiconductor portion 11 made of Si (silicon). The component of the semiconductor portion 11 is n-type Si. The semiconductor portion 11 has a first surface 111 and a second surface 112 located on the back 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.

At the center of the first surface 111, a first electrode 12 is provided, which is an electrode that outputs a signal when radiation is detected. The number of 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, a plurality of curved electrodes 14 in a multiple ring shape are provided on the first surface 111. 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 plurality of curved electrodes 14 arranged in a ring shape are almost concentric, and the first electrode 12 is located almost at the center of the plurality of curved electrodes 14. In other words, the plurality of curved electrodes 14 surround the first electrode 12, and the distance between the first electrode 12 and each curved electrode 14 is different.

Although five curved electrodes 14 are shown in FIG. 2, 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.

A ring-shaped protective electrode 151 is provided on the outside of the multiple curved electrodes 14, and a ring-shaped ground electrode 152 is provided on the outside of the protective electrode 151. The ground electrode 152 is connected to a ground potential. The potential of the protective electrode 151 is a floating potential. The protective electrode 151 prevents dielectric breakdown between the curved electrode 14 and the ground electrode 152. Although a single protective electrode 151 is shown in FIG. 2, in reality, multiple ring-shaped protective electrodes 151 are provided.

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 components of the second electrode 13 are p-type Si doped with a specific dopant such as boron, for example, p+Si. The second electrode 13 is formed over most of the area of the second surface 112, including the center of the second surface 112.

A ring-shaped protective electrode 16 is provided on the outside of the second electrode 13. The potential of the protective electrode 16 is a floating potential. Although a single protective electrode 16 is shown in FIG. 2, in reality, a plurality of protective electrodes 16 are provided in a multiple ring shape. The protective electrode 16 prevents dielectric breakdown between the edge of the semiconductor portion 11 and the second electrode 13. The radiation detection element 1 may not have a ground electrode 152 on the first surface 111 side, and may have a ground electrode on the second surface 112 side. That is, the ground electrode 152 may not be provided, and a ground electrode may be provided outside the protective electrode 16. In this form, the protective electrode 16 prevents dielectric breakdown between the second electrode 13 and the ground electrode. The radiation detection element 1 may have a ground electrode on both the first surface 111 side and the second surface 112 side.

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 also configured so that a predetermined electrical resistance occurs between adjacent curved electrodes 14 that are different from each other in distance 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. In addition, the multiple curved electrodes 14 may include a pair of adjacent curved electrodes 14 that have the same potential.

The potential of the multiple curved electrodes 14 generates an electric field (potential gradient) within the semiconductor portion 11 such that the potential is higher the closer to the first electrode 12 and lower the farther from the first electrode 12. The second electrode 13 is also 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 within the semiconductor portion 11 such that the potential is higher the closer to the first electrode 12.

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.

The preamplifier 21 is connected to the first electrode 12. The 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 arranged outside the radiation detector 2.

Figure 3 is a schematic cross-sectional view showing an example of the configuration of the radiation detector 2. The radiation detector 2 is an SDD (Silicon Drift Detector). The radiation detector 2 has a housing 23 in the shape of a cylinder with a truncated cone connected to one end. The housing 23 is configured with a plate-shaped bottom plate covered 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.

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

The radiation detector 2 may not include a 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 that does not include a cooling unit 25. The radiation detector 2 may be in a form that does not include a window 24 made of a window material, and the portion of the housing 23 that corresponds to the window 24 is open. Alternatively, the radiation detector 2 may be in a form that does not include a housing 23.

The radiation detector 2 has 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.

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. Therefore, radiation can be incident on the entire semiconductor portion 11 of the radiation detection element 1.

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 the portion where the first electrode 12 is provided and most of the 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.

Figure 4 is a graph showing a schematic representation of the electric field strength inside the semiconductor portion 11. The horizontal axis in the figure indicates the position inside the semiconductor portion 11 in the direction along the first surface 111. The center shown in the figure 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 figure is the position of the outer edge of the semiconductor portion 11. The vertical axis in the figure indicates the electric field strength. Figure 4 shows the electric field strength 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.

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. For this reason, the first electrode 12 collects almost all of the generated electrons in a short 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.

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 strength is lower in the unique region 114 than in the main region 113. In the unique region 114, the electric field strength is low, so it takes longer 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 strength, the more widely the electrons diffuse, and the greater the proportion of electrons that cannot flow into the first electrode 12. Therefore, the amount of charge acquired by the first electrode 12 due to the incidence of radiation on the unique region 114 is reduced compared to the amount of charge acquired by the first electrode 12 due to 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, processing is performed to prevent the radiation energy from being underdetected.

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 an amount of electrons according to the energy of the incident radiation at the first electrode 12, and outputs a current signal according 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 staircase wave whose signal value rises in a step-like manner when radiation is detected. The radiation detector 2 outputs a signal including the staircase wave generated by the preamplifier 21. The preamplifier 21 corresponds to a signal output unit.

Figure 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 the signal value. Each time radiation is incident on the radiation detection element 1 and an event occurs in which 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 the 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.

7 is a schematic graph showing an example of a step wave that continues for a long time. The horizontal axis in the figure shows time, and the vertical axis shows the signal value. FIG. 7 shows a step wave that continues for a longer time than the step wave shown in FIG. 6. If it takes a long time for electrons generated by radiation to flow into the first electrode 12, the time for the signal value to rise in steps becomes longer, and the step wave continues for a longer time. The lower the electric field intensity in the semiconductor part 11, the longer the time it takes for electrons generated by radiation to flow into the first electrode 12, so the step wave continues for a longer time. Therefore, the step wave caused by the charge (electrons) generated in the singular region 114 by the incidence of radiation continues for a longer time than the step wave caused by the charge generated in the main region 113. 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 singular region 114.

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 consists of multiple discrete signal values.

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 offset 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.

The trapezoid shaping unit 321 is configured using a trapezoid shaping filter. The trapezoid shaping unit 321 converts the step wave contained 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 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 a signal from the trapezoid shaping unit 321 and measures the wave height of the trapezoid wave contained in the signal.

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

The feature amount measurement unit 332 is connected to the differentiation unit 331. For example, the feature amount measurement unit 332 is configured using a processor that performs calculations. The feature amount measurement unit 332 measures a feature amount corresponding to the time that the step wave continues from the derivative of the step wave. The feature amount measurement 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 derivative of the step wave as the feature amount of the step wave.

Figure 8 is a schematic graph showing an example of a step wave and its differential waveform to explain 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 Figure 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 predetermined. 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, and the step wave caused by the charge generated in the unique region 114 has a long time width.

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. 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 derivative of the staircase wave.

When the time required for the 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 smaller. The slope of the differential waveform becomes smaller. Conversely, when the time required for the 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 point 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 point. 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 the reference value for defining the time width of the staircase wave, or it may be different. Alternatively, the reference value may be a value that is a predetermined percentage of the maximum differential value of the step wave, such as 1/10 of the maximum differential value of the step wave. The value of the second 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 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 differential at the time when the differential value becomes the reference value is small.

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

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 the staircase wave is caused by the charge generated in the singular 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.

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

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

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

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 charge is generated and the easier it is for the electrons to spread over a wide area. This means that it takes longer for the electrons to flow into the first electrode 12, and the longer the staircase wave lasts. Even if the staircase wave is caused by charge generated in the main region 113, the greater the energy of the incident radiation, the longer the staircase wave lasts. The greater the energy of the radiation, the greater the height of the staircase wave and the longer the staircase wave lasts. The threshold of the characteristic quantity is determined for each wave height so that the length of time of the staircase wave corresponding to the threshold increases monotonically as the wave height of the staircase wave increases.

For example, the threshold for the time width of the step wave is set for each wave height so as to monotonically increase as the wave height of the step wave increases. For example, the threshold for the maximum value of the slope of the step wave is set for each wave height so as to monotonically decrease as the wave height of the step wave increases. For example, the threshold for the value of the second derivative of the step wave at the point where the derivative value of the step wave becomes the reference value is set for each wave height so as to monotonically decrease as the wave height of the step wave increases. Since the thresholds are set in this way, 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 possible to accurately determine whether the step wave is caused by the charge generated in the unique region 114.

The processing unit 34 stores in advance a threshold value of a predetermined characteristic 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 characteristic amount of the step wave calculated by the characteristic amount measuring unit 332 to determine whether or not the step wave is caused by the charge generated in the singular region 114.

The processing unit 34 may have a constant threshold value for the feature amount, and may correct the feature amount according to the wave height of the step wave when determining whether the step wave is caused by the charge generated in the unique region 114. In this embodiment, the processing unit 34 corrects the feature amount so that the time length 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 a threshold value for the time width of the step wave, and corrects the time width of the step wave so that it monotonically decreases with an increase in the wave height of the step wave when determining whether the step wave is caused by the charge generated in the unique region 114. The processing unit 34 compares the threshold value with the corrected time width to determine whether the step wave is caused by the charge generated in the unique region 114.

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 the 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 when determining whether or not the staircase wave is caused by the charge generated in the singular region 114, 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 the 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.

In this way, even in a configuration in which 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 a step wave caused by the charge generated in the unique region 114. Therefore, it is possible to accurately determine whether or not the step wave is caused by the charge generated in the unique region 114.

The counting unit 35 is connected to the processing unit 34. The counting unit 35 counts step waves by 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.

When the staircase wave is not caused by the charge generated in the singular region 114, i.e., 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 that is not caused by the charge generated in the singular region 114. When the staircase wave is caused by the charge generated in the singular 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 singular region 114.

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.

Figure 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.

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

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 memory unit 44. The calculation unit 41 executes the 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 memory unit 44. In these cases, the analysis device 4 may not have a 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.

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 or quantitative analysis of the 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 radiation.

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).

The A/D converted signal is subjected to wave 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 wave height measurement unit 322 measures the wave height of the trapezoidal wave to measure the wave height of the step wave contained in the signal. In addition, 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 derivative of the step wave at the point when the differential value of the step wave becomes a reference value.

The processing unit 34 determines whether the staircase wave is caused by the charge generated in the singular region 114 based on the feature amount measured by the feature amount measurement unit 332 (S14). If the staircase wave is not caused by the charge generated in the singular 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 measurement unit 322 (S15). In S15, the counting unit 35 adds +1 to the previous count number. The staircase wave caused by the charge generated in the main region 113 is counted by the processes of S14 and S15. 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 singular region 114 (S14: YES), the processing unit 34 ends the process without issuing an instruction to count. In other words, if the staircase wave is caused by charges generated in the unique region 114, the signal processing device 3 does not count the staircase wave.

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, if the step wave is caused by charges 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 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.

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 charge generated in the unique region 114, but includes the number of step waves caused by the charge 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, a decrease in the accuracy of radiation detection is sufficiently suppressed.

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. Because 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 is improved. Because the collimator does not block the radiation incident on the main region 113, which has a high electric field strength, the sensitivity of radiation detection is improved. Furthermore, by not providing a collimator, the cost of the radiation detector 2 is reduced.

<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, wave-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.

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 the charge generated in the singular region 114 based on the feature amount of the staircase wave calculated by the feature amount measuring unit 332.

When the staircase wave is not caused by charges generated in the singular 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 singular 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 singular region 114.

Figure 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 A/D converts the input signal (S22). The A/D converted signal is subjected to wave height measurement and feature measurement (S23). In S23, the trapezoid shaping unit 321 converts the signal waveform into a trapezoid wave, and the wave height measurement unit 322 measures the wave height of the step wave. In addition, the differentiation unit 331 differentiates the signal, and the feature measurement unit 332 calculates the feature amount of the step wave. For example, the feature measurement 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 derivative of the step wave at the point when the differential value of the step wave becomes a reference value as the feature amount of the step wave.

The processing unit 34 determines whether the staircase wave is caused by charges generated in the unique region 114 based on the features measured by the feature measurement unit 332 (S24). If the staircase wave is not caused by charges generated in the unique region 114 (S24: NO), the wave-height measurement unit 322 outputs information including the measured wave height 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.

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 processing of S24 to S26, the step waves caused by the charge generated in the main region 113 are counted by wave height. After the processing of S26 is completed, the signal processing device 3 and the analysis device 4 end the processing.

If the staircase wave is caused by charges generated in the unique region 114 (S24: YES), the processing unit 34 ends the process as is. In other words, if the staircase 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 staircase wave to the analysis device 4, and the analysis device 4 does not count the staircase 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 staircase wave when the staircase 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.

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 wave height stored in the memory unit 44. The calculation unit 41 displays the spectrum of the radiation on the display unit 53. In the second embodiment, the spectrum does not include detection results of radiation in which the energy is detected as being underestimated, 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 also execute part or all of the processing in the processing unit 34.

In the second embodiment, the decrease in the accuracy of radiation detection is suppressed without using a collimator. As in the first embodiment, the accuracy of radiation detection is improved and the sensitivity of radiation detection is improved by not including a collimator in the radiation detector 2. In addition, the cost of the radiation detector 2 is reduced.

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 staircase wave, but the signal processing device 3 may be configured to calculate the wave height of the staircase wave by integrating the differential waveform generated by the differentiation unit 331. In the first and second embodiments, the functions of the signal processing device 3 are realized by hardware, but the signal processing device 3 may be configured to realize some or all of its functions by software.

In the first and second embodiments, the determination is based on the feature amount of the staircase wave, but the signal processing device 3 may be configured to perform the 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 singular region 114 when the waveform of the staircase wave or the differential waveform of the staircase wave is input. The learning model is pre-trained using training data including the waveform or differential waveform of the staircase wave caused by the charge generated in the main region 113 and the waveform or differential waveform of the staircase wave caused by the charge generated in the singular 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 singular region 114.

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 peculiar region 114. Even if radiation passes through the collimator and enters the peculiar region 114, the step wave caused by the charge generated in the peculiar region 114 is not counted, thereby preventing the radiation energy from being underdetected. Therefore, in addition to the effect of the collimator suppressing a decrease in the accuracy of radiation detection, a decrease in the accuracy of radiation detection is more effectively suppressed.

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.

In the first and second embodiments, the semiconductor constituting the radiation detection element 1 is Si, but the radiation detection element 1 may be made of a semiconductor other than Si. In the first and second embodiments, the semiconductor portion 11 is made of an n-type semiconductor, and the second electrode 13 is made of a p-type semiconductor, but the radiation detection element 1 may be made of a p-type semiconductor, and the second electrode 13 is made of an n-type semiconductor. In this embodiment, holes are collected in the first electrode 12 as charges. In the first and second embodiments, the radiation detection element 1 is 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 a semiconductor element. Therefore, the radiation detector 2 may be a radiation detector other than an SDD.

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 is transmitted through or 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.

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 that are appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

REFERENCE SIGNS LIST 10 Radiation detection device 1 Radiation detection element 11 Semiconductor section 12 First electrode 13 Second electrode 2 Radiation detector 21 Preamplifier 3 Signal processing device 332 Feature amount measuring section 34 Processing section 35 Counting section 4 Analysis device 40 Recording medium 441 Computer program

Claims (8)

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: 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: 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: 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. The radiation detection device according to claim 3, further comprising no collimator for blocking a portion of the radiation incident on the semiconductor portion. 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;
The radiation detection device according to claim 3 , further comprising: a display unit that displays the spectrum generated by the spectrum generating unit. 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. 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.

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