Information processing method, computer program, information processing apparatus, and radiation detection device

Abstract

Provided are an information processing method, a computer program, an information processing apparatus, and a radiation detection device which make it possible to determine the energy and the intensity of a radiation.　A measured spectrum of a radiation detected by using a radiation detector is acquired. The energy and the intensity of the radiation are assumed. By performing Monte Carlo ray tracing using the assumed energy and intensity on a plurality of photons included in the radiation of which the energy and the intensity have been assumed, energies to be identified upon detection of the photons are calculated. A virtual spectrum of the radiation is generated by counting the number of the photons for each of the calculated energies. The assumed energy and intensity are modified on the basis of the comparison between the measured spectrum and the virtual spectrum. The modified energy and intensity are determined to be the energy and the intensity of the radiation.

Description

Information processing method, computer program, information processing device, and radiation detection device

[0001] The present invention relates to an information processing method, a computer program, an information processing device, and a radiation detection device for analyzing detected radiation.

[0002] A radiation detector has a radiation detection element such as a semiconductor radiation detection element. In radiation detection, radiation incident on the radiation detector is counted by energy through interaction with the radiation detection element, and a spectrum representing the relationship between the radiation energy and the count number is generated. Ideally, the spectrum should contain only peaks corresponding to the energy of the radiation incident on the radiation detector. However, in reality, many peaks may occur due to various phenomena, such as phenomena caused by radiation within the radiation detection element and phenomena caused by radiation incident on materials other than the radiation detection element. Peaks caused by signal processing, such as so-called sum peaks, may also occur. In an actual spectrum, many generated peaks may overlap, making it difficult to determine the energy and intensity of the detected radiation.

[0003] Patent No. 3412606

[0004] Patent Document 1 discloses a technique for analyzing the characteristics of a condenser lens using a ray tracing technique in the field of particle size distribution measurement using the diffraction and scattering of laser light. In radiation detection, it is also desirable to use the ray tracing technique to determine the energy and intensity of detected radiation.

[0005] An object of the present invention is to provide an information processing method, a computer program, an information processing device, and a radiation detection device that are capable of determining the energy and intensity of radiation.

[0006] An information processing method according to the present invention is characterized in that it acquires a measured spectrum of radiation detected using a radiation detector, assumes the energy and intensity of the radiation, and performs Monte Carlo ray tracing using the assumed energy and intensity for each of a plurality of photons contained in the radiation, whose energy and intensity have been assumed, to calculate the energy specified when each photon is detected, and counts the number of photons for each calculated energy to generate a virtual spectrum of the radiation, and modifies the assumed energy or intensity in accordance with a comparison between the measured spectrum and the virtual spectrum, and determines the modified energy and intensity as the energy and intensity of the radiation.

[0007] In one aspect of the present invention, the energy and intensity of detected radiation are assumed, and the energy at which each photon contained in the radiation is detected is calculated using Monte Carlo ray tracing to generate a virtual spectrum of the radiation. The energy and intensity of the assumed radiation are modified according to a comparison between the actual spectrum of the radiation and the virtual spectrum. The energy and intensity of the assumed radiation can be modified so that the actual spectrum and the virtual spectrum approximately match, and the modified energy and intensity of the radiation can be determined as the energy and intensity of the detected radiation.

[0008] The information processing method according to the present invention is characterized in that, in the Monte Carlo ray tracing, an object that interacts with each photon is identified, a type of interaction between each photon and the object is determined probabilistically, the energy or direction of the photon that changes due to the interaction is calculated probabilistically, and the energy of the photon that is detected as a result of the interaction between the photon and a radiation detection element included in the radiation detector is calculated.

[0009] In one aspect of the present invention, Monte Carlo ray tracing involves identifying an object that interacts with a photon and probabilistically determining the type of interaction. Furthermore, it involves probabilistically calculating the energy or direction of the photon that changes due to the interaction, and calculating the energy of the photon that is detected due to the interaction. In this way, ray tracing of each photon contained in the radiation is performed, and it is calculated what energy the photon ultimately has when it is detected.

[0010] The information processing method according to the present invention is characterized in that, in the Monte Carlo ray tracing, the flight distance of each photon is calculated probabilistically, and objects that interact with each photon are identified based on the position and size of each object included in the radiation detector and the flight distance.

[0011] In one aspect of the present invention, Monte Carlo ray tracing involves probabilistically calculating the flight distance of a photon and using the flight distance to identify an object that interacts with the photon. By using the probabilistically calculated flight distance, it becomes possible to easily perform processing to identify an object that interacts with the photon.

[0012] The information processing method according to the present invention is characterized in that it probabilistically determines whether the time interval at which multiple photons whose energies have been calculated are detected is short or not, and modifies the energy calculated using the Monte Carlo ray tracing by adding up the energies of multiple photons whose detection intervals are determined to be short, and setting the sum of the energies of the multiple photons whose detection intervals are determined to be short as the energy of a single photon.

[0013] In one aspect of the present invention, whether or not the time interval at which multiple photons are detected is short is determined probabilistically, and multiple photons detected at a short time interval are considered to be detected as a single photon, and the energy of the single photon is the sum of some or all of the energies of the multiple photons, thereby generating a virtual spectrum including a sum peak.

[0014] An information processing method according to the present invention is characterized in that it includes: storing a first virtual spectrum of radiation calculated by performing Monte Carlo ray tracing on each of a plurality of photons contained in the radiation in association with the energy and intensity of the radiation; acquiring an actual measured spectrum of the radiation detected using a radiation detector; assuming the energy and intensity of the radiation; generating a second virtual spectrum of the radiation based on the first virtual spectrum stored in association with the energy and intensity corresponding to the assumed energy and intensity; correcting the assumed energy or intensity of the radiation in accordance with a comparison between the actual measured spectrum and the second virtual spectrum; and determining the corrected energy and intensity as the energy and intensity of the radiation detected using the radiation detector.

[0015] In one aspect of the present invention, a process is performed in which the energy and intensity of the detected radiation are assumed, and a second virtual spectrum of the radiation is generated using a first virtual spectrum corresponding to the assumed energy and intensity. The assumed energy and intensity are modified based on a comparison between the actual spectrum of the radiation and the second virtual spectrum. The assumed energy and intensity of the radiation can be modified so that the actual spectrum and the second virtual spectrum approximately match, and the modified energy and intensity can be determined as the energy and intensity of the detected radiation.

[0016] The information processing method according to the present invention is characterized in that it acquires a measured spectrum of radiation emitted from a sample, and performs elemental analysis of the sample based on the determined energy and intensity of the radiation.

[0017] In one aspect of the present invention, an actual spectrum of radiation emitted from a sample is acquired, and elemental analysis of the sample is performed based on the determined energy and intensity of the radiation. Based on the accurately determined energy and intensity of the radiation, it becomes possible to perform elemental analysis of the sample with high accuracy.

[0018] A computer program according to the present invention causes a computer to execute the following processes: for each of a plurality of photons contained in radiation, whose energy and intensity are assumed, calculate the energy specified when each photon is detected using a radiation detector by performing Monte Carlo ray tracing using the assumed energy and intensity; by counting the number of photons for each calculated energy, generate a virtual spectrum of the radiation; modify the assumed energy or intensity in accordance with a comparison between the actual spectrum of the radiation detected using the radiation detector and the virtual spectrum; and determine the modified energy and intensity as the energy and intensity of the radiation detected using the radiation detector.

[0019] In one aspect of the invention, a computer program determines the energy and intensity of the radiation using Monte Carlo ray tracing.

[0020] An information processing device according to the present invention includes a calculation unit that acquires a measured spectrum of radiation detected using a radiation detector, assumes the energy and intensity of the radiation, and performs Monte Carlo ray tracing using the assumed energy and intensity for each of a plurality of photons contained in the radiation, the energy and intensity of which have been assumed, to calculate the energy specified when each photon is detected, and generates a virtual spectrum of the radiation by counting the number of photons for each calculated energy, and modifies the assumed energy or intensity in accordance with a comparison between the measured spectrum and the virtual spectrum, and determines the modified energy and intensity as the energy and intensity of the radiation.

[0021] In one aspect of the present invention, an information processing device including a calculation unit determines the energy and intensity of radiation using Monte Carlo ray tracing.

[0022] In the information processing device according to the present invention, the calculation unit has a parallel calculation unit, and the parallel calculation unit executes in parallel a process of calculating, for each of a plurality of photons, the energy identified when each photon is detected by performing the Monte Carlo ray tracing.

[0023] In one aspect of the present invention, the calculation unit includes a parallel calculation unit, and the parallel calculation unit executes the Monte Carlo ray tracing process in parallel for a plurality of photons contained in the radiation, thereby executing the Monte Carlo ray tracing process for a large number of photons contained in the radiation at high speed.

[0024] A radiation detection apparatus according to the present invention is characterized by comprising an irradiation unit that irradiates a sample with radiation, a radiation detector that detects radiation from the sample, and the information processing apparatus according to the present invention.

[0025] In one aspect of the present invention, a radiation detection device includes an irradiation unit that irradiates a sample with radiation, a radiation detector that detects radiation from the sample, and an information processing device. The information processing device accurately determines the energy and intensity of the radiation by a process of determining the energy and intensity of the radiation using Monte Carlo ray tracing, and is able to accurately perform elemental analysis of the sample.

[0026] The present invention has excellent effects such as being able to determine the energy and intensity of radiation detected by the radiation detector.

[0027] 1 is a block diagram showing an example of the functional configuration of a radiation detection device; FIG. 2 is a schematic cross-sectional view showing an example of the configuration of a radiation detector; FIG. 3 is a schematic cross-sectional view showing an example of the configuration of a radiation detection element and a collimator; FIG. 4 is a block diagram showing an example of the internal configuration of an analysis unit according to embodiment 1; FIG. 5 is a view showing an example of the spectrum of radiation having a single energy; FIG. 6 is a view showing an example of the spectrum of radiation generated when radiation having a single energy is incident on a radiation detector; FIG. 7 is a flowchart showing an example of the processing procedure executed by the analysis unit according to embodiment 1; FIG. 8 is a flowchart showing an example of the processing procedure of Monte Carlo ray tracing; FIG. 9 is a block diagram showing an example of the internal configuration of an analysis unit according to embodiment 2;

[0028] The present invention will be described in detail below with reference to the drawings illustrating embodiments. <Embodiment 1> Fig. 1 is a block diagram showing an example of the functional configuration of a radiation detection apparatus 100. The radiation detection apparatus 100 is, for example, an X-ray fluorescence analysis apparatus. The radiation detection apparatus 100 includes an irradiation unit 26 that irradiates a sample 4 with radiation such as an electron beam or X-rays, a sample stage 27 on which the sample 4 is placed, and a radiation detector 1. Radiation is irradiated from the irradiation unit 26 to the sample 4, causing radiation such as fluorescent X-rays to be generated in the sample 4, and the radiation detector 1 to detect the radiation generated from the sample 4. In the figure, the radiation is indicated by arrows. Note that the radiation detection apparatus 100 may also be configured to hold the sample 4 by a method other than placing it on the sample stage 27.

[0029] The radiation detector 1 includes a radiation detection element 11 and a preamplifier 12. A part of the preamplifier 12 may be included inside the radiation detector 1, with the other part being arranged outside the radiation detector 1. The radiation detector 1 is connected to a voltage application unit 21 that applies a voltage required for radiation detection to the radiation detection element 11, and a signal processing unit 22. The voltage application unit 21 also applies a voltage required for the preamplifier 12 to operate, to the preamplifier 12. The signal processing unit 22 is connected to an analysis unit 3. The analysis unit 3 is configured using a computer.

[0030] The radiation detection device 100 includes a control unit 25. The control unit 25 is connected to the voltage application unit 21, the signal processing unit 22, the analysis unit 3, and the irradiation unit 26. The control unit 25 controls the operations of the voltage application unit 21, the signal processing unit 22, the analysis unit 3, and the irradiation unit 26. For example, the control unit 25 is configured using a computer having a calculation unit and a memory. The control unit 25 and the analysis unit 3 are connected to an operation unit 23 and a display unit 24. The operation unit 23 receives input of information such as text by receiving operations from the user. The operation unit 23 is, for example, a touch panel, a keyboard, or a pointing device. The display unit 24 displays images. The display unit 24 is, for example, a liquid crystal display or an electroluminescent display (EL display). The control unit 25 may be configured to receive operations from the user using the operation unit 23 and control each unit of the radiation detection device 100 in accordance with the received operations.

[0031] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the radiation detector 1. The radiation detector 1 is an SDD (Silicon Drift Detector). The radiation detector 1 includes a housing 16 shaped like a cylinder with a truncated cone connected to one end. The housing 16 includes a plate-shaped bottom plate covered with a cap-shaped cover. A window 161 made of a window material that transmits radiation is provided at the tip of the housing 16. The radiation detection element 11, the collimator 13, the circuit board 14, the Peltier element 15, and the cold finger 17 are arranged inside the housing 16. The housing 16 accommodates the radiation detection element 11, the collimator 13, the circuit board 14, and the Peltier element 15. The housing 16 accommodates the radiation detection element 11, physically protects the radiation detection element 11, and shields it from light. The shape of the housing 16 is not limited to the shape shown in FIG. 2 and may be other shapes.

[0032] The radiation detection element 11 is mounted on the surface of the circuit board 14 and is disposed in a position facing the window 161. The collimator 13 is cylindrical with both ends open and made of a radiation-shielding material. The collimator 13 is disposed between the radiation detection element 11 and the window 161. Radiation mainly passes through the window 161 and enters the inside of the housing 16, and the collimator 13 blocks part of the radiation. The radiation detection element 11 detects incident radiation that is not blocked by the collimator 13.

[0033] A circuit is formed on the circuit board 14, and the preamplifier 12 is mounted on it. The back surface of the circuit board 14 is in thermal contact with one end of the Peltier element 15, either directly or via an intervening object. The other end of the Peltier element 15 is in thermal contact with the cold finger 17. The cold finger 17 has a flat portion with which the other end of the Peltier element 15 is in thermal contact, and a portion that penetrates the bottom plate of the housing 16. Heat from the radiation detection element 11 is absorbed by the Peltier element 15 through the circuit board 14. The heat is conducted from the Peltier element 15 to the cold finger 17 and dissipated to the outside of the radiation detector 1 through the cold finger 17.

[0034] The radiation detector 1 includes a plurality of lead pins 18 that penetrate the bottom plate of the housing 16. The lead pins 18 are connected to the circuit board 14 by a method such as wire bonding. The application of voltage to the radiation detection element 11 by the voltage application unit 21 and the output of a signal from the preamplifier 12 are performed through the lead pins 18. The radiation detector 1 may further include other components.

[0035] FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the radiation detection element 11 and the collimator 13. The radiation detection element 11 is a silicon drift type radiation detection element. The radiation detection element 11 is generally flat. The radiation detection element 11 includes a plate-shaped semiconductor portion 112 made of Si (silicon). The radiation detection element 11 has an incident surface 111 located on the incident side where radiation to be detected is incident, and an electrode surface 116 located on the back side of the incident surface 111. A portion of the incident surface 111 is covered with the collimator 13. The radiation detection element 11 is arranged so that the electrode surface 116 faces the circuit board 14 and the incident surface 111 faces the window 161. An electrode layer 113 is provided on a portion of the semiconductor portion 112 on the incident surface 111 side.

[0036] A signal output electrode 115, which is an electrode that outputs a signal when radiation is detected, and a plurality of curved electrodes 114 that are multiple annular in plan view are provided in a portion of the semiconductor portion 112 on the electrode surface 116 side. The plurality of curved electrodes 114 surround the signal output electrode 115, and the distance between the signal output electrode 115 and each curved electrode 114 varies. Although four curved electrodes 114 are shown in FIG. 3 , more curved electrodes 114 are actually provided. The innermost curved electrode 114 and the outermost curved electrode 114 are connected to a voltage application unit 21. The electrode layer 113 is also connected to the voltage application unit 21. When a voltage is applied from the voltage application unit 21 to the curved electrodes 114 and the electrode layer 113, an electric field (potential gradient) is generated inside the semiconductor portion 112, with the potential increasing toward the signal output electrode 115.

[0037] Radiation is irradiated from the irradiation unit 26 onto the sample 4. The irradiated sample 4 generates radiation consisting of characteristic X-rays such as fluorescent X-rays. The radiation generated from the sample 4 enters the radiation detector 1. The radiation consisting of characteristic X-rays mainly passes through the window 161 and enters the interior of the radiation detector 1. A portion of the radiation that enters the interior of the radiation detector 1 enters the radiation detection element 11 and then enters the semiconductor portion 112. The radiation is absorbed within the semiconductor portion 112, and electrons and holes are generated in amounts corresponding to the energy of the absorbed radiation. In this embodiment, the electric field within the semiconductor portion 112 causes electrons to move and flow into the signal output electrode 115. The signal output electrode 115 outputs a current signal according to the electrons that have flowed in.

[0038] The semiconductor portion 112 includes a sensitive region 117 capable of detecting radiation. The region surrounded by a dashed line in FIG. 3 is the sensitive region 117. The sensitive region 117 includes the central portion of the semiconductor portion 112 and most of the semiconductor portion 112 except for the portion close to the periphery of the semiconductor portion 112. Compared to the central portion of the semiconductor portion 112, the portion close to the periphery of the semiconductor portion 112 has a weaker electric field, making it difficult for electrons generated by incident radiation to move to the signal output electrode 115. The portion close to the periphery of the semiconductor portion 112 is covered by the collimator 13, making it difficult for radiation to be incident thereon. The sensitive region 117 is the portion not covered by the collimator 13. Furthermore, the region of the semiconductor portion 112 close to the incident surface 111 and the region close to the electrode surface 116 are not included in the sensitive region 117.

[0039] The signal output electrode 115 is connected to the preamplifier 12. The signal output by the signal output electrode 115 is input to the preamplifier 12. The preamplifier 12 converts the current signal into a voltage signal. The preamplifier 12 is connected to the signal processing unit 22. When the preamplifier 12 outputs a signal, the radiation detector 1 outputs a signal of an intensity corresponding to the energy of the radiation to the signal processing unit 22. The signal processing unit 22 receives the signal output by the radiation detector 1 and determines the signal intensity, thereby detecting the signal intensity corresponding to the energy of the radiation detected by the radiation detector 1. The signal processing unit 22 counts the signals by signal intensity, and outputs data indicating the relationship between the signal intensity and the count number to the analysis unit 3.

[0040] The analysis unit 3 receives data indicating the relationship between the signal intensity and the count number output by the signal processing unit 22. The analysis unit 3 generates a spectrum of the radiation incident on the radiation detector 1 based on the data from the signal processing unit 22. Since the signal intensity corresponds to the energy of the radiation and the count number corresponds to the number of times the radiation is detected, i.e., the intensity of the radiation, the spectrum of the radiation can be obtained from the relationship between the signal intensity and the count number. The spectrum represents the relationship between the energy of the radiation and the intensity of the radiation. The process of counting the signals output by the radiation detector 1 by signal intensity may be performed by the analysis unit 3 instead of the signal processing unit 22. The generation of the radiation spectrum may be performed by the signal processing unit 22. The analysis unit 3 stores spectral data representing the spectrum of the radiation. The display unit 24 displays the spectrum of the radiation.

[0041] FIG. 4 is a block diagram showing an example of the internal configuration of the analysis unit 3 according to the first embodiment. The analysis unit 3 is an information processing device that executes an information processing method. The analysis unit 3 is configured using a computer such as a personal computer. The analysis unit 3 includes a calculation unit 31, a memory 32, a reading unit 33, a storage unit 34, an interface unit 35, and a parallel calculation unit 36. The calculation unit 31 is a processor and is configured using, for example, a central processing unit (CPU), a graphics processing unit (GPU), a multi-threaded CPU, or a multi-core CPU. The calculation unit 31 may also be configured using a quantum computer. The memory 32 stores temporary data generated in conjunction with calculations. The memory 32 is, for example, a random access memory (RAM). The reading unit 33 reads information from a recording medium 30 such as an optical disk or a portable memory. The storage unit 34 is non-volatile and is, for example, a hard disk or a non-volatile semiconductor memory. The parallel calculation unit 36 ​​is a device for executing multiple calculations in parallel. For example, the parallel computing unit 36 ​​is configured using a GPU. The arithmetic unit 31 and the parallel computing unit 36 ​​correspond to a computing unit.

[0042] The calculation unit 31 causes the reading unit 33 to read a computer program (program product) 341 recorded on the recording medium 30, and stores the read computer program 341 in the storage unit 34. The calculation unit 31 executes processing required for the analysis unit 3 in accordance with the computer program 341. The computer program 341 may be downloaded from outside the analysis unit 3. Alternatively, the computer program 341 may be stored in advance in the storage unit 34. In these cases, the analysis unit 3 does not need to include the reading unit 33.

[0043] The computer program 341 can be deployed to run on a single computer, or on multiple computers located at one site or distributed across multiple sites and interconnected by a communications network. That is, the analysis unit 3 may be configured with multiple computers, and the computer program 341 may be executed on multiple computers connected via a communications network. The analysis unit 3 may be configured using a cloud server. The analysis unit 3 and the control unit 25 may be configured with the same computer.

[0044] The processing of each step described below for executing the information processing method can be executed by multiple computers. The processing of each step can also be executed by different computers. Data used during the processing can be stored in multiple computers. The processing of each step can also be executed using a virtual machine. The processing of each step can be executed by multiple computing units. The processing of each step can also be executed by different computing units. For example, part of the processing can be executed by one computer, and another part of the processing can be executed by another computer.

[0045] The analysis unit 3 is connected to an operation unit 23 and a display unit 24. The interface unit 35 is connected to a signal processing unit 22 and a control unit 25. A user operates the operation unit 23 to input various instructions, such as an instruction to start analysis, to the analysis unit 3. The analysis unit 3 accepts the instructions input using the operation unit 23. The display unit 24 displays an image. The analysis unit 3 outputs information necessary for radiation detection or analysis of the sample 4 by displaying an image including the information on the display unit 24. The analysis unit 3 accepts information from the signal processing unit 22 and the control unit 25 via the interface unit 35. Some or all of the processing for executing the information processing method may be executed by a computer external to the radiation detection device 100, and the analysis unit 3 may transmit information necessary for processing to the external computer and obtain processing results from the external computer.

[0046] The radiation spectrum generated by the analysis unit 3 indicates the relationship between the energy and intensity of the radiation incident on the radiation detector 1. Radiation is made up of multiple photons, and the intensity of the radiation corresponds to the number of photons contained in the radiation. The radiation is detected by detecting each photon. In the radiation spectrum, each energy is associated with the intensity of the radiation having that energy, i.e., the number of detected photons having that energy.

[0047] Fig. 5 is a diagram showing the spectrum of radiation having a single energy. In the diagram, the horizontal axis represents the radiation energy, and the vertical axis represents the radiation intensity. The spectrum includes a peak corresponding to the radiation energy. When radiation having a single energy is incident on the radiation detector 1, ideally, a spectrum including only a single peak as shown in Fig. 5 should be obtained.

[0048] However, in reality, peaks and background other than the peak corresponding to the radiation energy occur due to various phenomena occurring in the radiation detector 1. Peaks may also occur due to signal processing. As a result, a complex spectrum is generated in which many peaks and backgrounds overlap. FIG. 6 is a diagram showing an example of a radiation spectrum generated when radiation having a single energy is incident on the radiation detector 1. The horizontal axis in the diagram represents the radiation energy, and the vertical axis represents the radiation intensity. FIG. 6 shows an example of a spectrum generated when radiation whose energy is shown in FIG. 5 is incident on the radiation detector 1. The spectrum includes a peak corresponding to the radiation energy, and also includes many peaks corresponding to other energies.

[0049] For example, when radiation is incident on an object, characteristic X-rays are generated, and characteristic X-rays having an energy different from that of the initial radiation are detected. For example, when radiation undergoes inelastic scattering, electrons generated by the inelastic scattering and radiation whose energy has attenuated are detected. For example, when radiation is detected multiple times at very short intervals, the signal processing unit 22 cannot separate the multiple signals corresponding to the multiple detections, and ends up detecting radiation having an energy equal to the sum of the energies of the multiple radiations. A peak caused by this phenomenon is a so-called sum peak, and the sum peak may correspond to an energy higher than the original energy of the radiation. Thus, the actually obtained spectrum contains many peaks corresponding to energies different from the original energy of the radiation due to various phenomena.

[0050] As shown in Fig. 6 , the spectrum of radiation actually obtained contains many peaks that differ from the original energy of the radiation, making it difficult to identify the energy and intensity of the radiation that entered the radiation detector 1 from the spectrum of radiation actually obtained. The analysis unit 3 performs information processing to identify the energy and intensity of the radiation that entered the radiation detector 1. More specifically, the analysis unit 3 calculates a hypothetical spectrum that could be obtained based on an assumption of the energy and intensity of the radiation, compares the actually obtained spectrum with the hypothetical spectrum, and adjusts the energy and intensity of the radiation to identify the energy and intensity of the radiation. Hereinafter, the hypothetical spectrum of radiation calculated based on an assumption of the energy and intensity of the radiation will be referred to as the hypothetical spectrum. Furthermore, the spectrum of radiation actually obtained by actually detecting radiation using the radiation detector 1 will be referred to as the measured spectrum.

[0051] The memory unit 34 stores information necessary for information processing to identify the energy and intensity of radiation. The memory unit 34 stores detector data including information about a plurality of objects included in the radiation detector 1. The detector data records the position, size, and material of each object included in the radiation detector 1. The detector data also records the material properties of each object. For example, the detector data records the type, absorption coefficient, and density of the elements contained as material properties.

[0052] The analysis unit 3 executes information processing to determine the energy and intensity of radiation, and performs elemental analysis of the sample 4 using the determined energy and intensity of radiation. FIG. 7 is a flowchart showing an example of the processing procedure executed by the analysis unit 3 according to the first embodiment. Hereinafter, steps are abbreviated as S. The calculation unit 31 executes information processing in accordance with the computer program 341, causing the analysis unit 3 to execute the following processing. The radiation detection device 100 irradiates the sample 4 with radiation from the irradiation unit 26, detects radiation emitted from the sample 4 using the radiation detector 1, and generates a spectrum of the detected radiation. The analysis unit 3 generates a spectrum of the detected radiation, thereby obtaining a measured spectrum of the radiation emitted from the sample 4 (S101). The calculation unit 31 stores spectral data representing the measured spectrum in the storage unit 34.

[0053] The analysis unit 3 assumes the energy and intensity of the detected radiation (S102). The energy of radiation is the energy of photons contained in the radiation, and the intensity of radiation corresponds to the number of photons contained in the radiation. In S102, the user operates the operation unit 23 to input assumed values ​​of the energy and intensity of the radiation, and the calculation unit 31 then assumes the energy and intensity of the radiation. In S102, the calculation unit 31 may assume the energy and intensity of the radiation to predetermined values ​​or may assume them randomly. In S102, the calculation unit 31 may perform a process of assuming the energy and intensity of the radiation based on the actually measured spectrum.

[0054] In S102, the calculation unit 31 may assume that the radiation contains multiple types of radiation with different energies, and may assume the energy and intensity of each of the multiple types of radiation. In S102, the calculation unit 31 may assume the energy and intensity of the radiation immediately before it enters the radiation detector 1, or may assume the energy and intensity of the radiation after it has passed through the window 161. The calculation unit 31 may also assume the spatial distribution of multiple photons contained in the radiation, or the traveling direction of each photon. The traveling direction of each photon may be determined probabilistically.

[0055] The analysis unit 3 then performs Monte Carlo ray tracing to track each of the multiple photons contained in the radiation (S103). The analysis unit 3 executes the process of S103 using the parallel calculation unit 36. The calculation unit 31 inputs information necessary for the calculation, such as the assumed energy and intensity of the radiation, to the parallel calculation unit 36, and causes the parallel calculation unit 36 ​​to execute the process. In S103, the parallel calculation unit 36 ​​executes calculations in parallel to track the multiple photons contained in the radiation using the assumed energy and intensity of the radiation.

[0056] 8 and 9 are flowcharts showing an example of the processing procedure of Monte Carlo ray tracing. The parallel computing unit 36 ​​selects one photon from multiple photons contained in radiation (S201). In S201, the parallel computing unit 36 ​​sets the assumed radiation energy as the initial value of the photon energy. The parallel computing unit 36 ​​sets the number of photons to a value corresponding to the assumed radiation intensity. The parallel computing unit 36 ​​also determines initial values ​​for the position and traveling direction of the photon.

[0057] The parallel computing unit 36 ​​stochastically calculates the flight distance of the selected photons (S202). The flight distance is a dimensionless quantity that represents the distance that the photons travel within the radiation detector 1. A representative value of the flight distance, such as an average value, or a probability distribution of the flight distance is determined in advance and stored in the storage unit 34. The parallel computing unit 36 ​​stochastically calculates the flight distance.

[0058] The parallel computing unit 36 ​​determines whether the photon is incident on any object within the radiation detector 1 (S203). In S203, the parallel computing unit 36 ​​tracks the selected photon. For example, the parallel computing unit 36 ​​tracks the photon assuming that the photon travels in a straight line while consuming its flight distance. The amount of flight distance consumed in air is calculated according to the absorption coefficient of air. The parallel computing unit 36 ​​determines whether the photon is incident on an object based on the position and size of each object included in the radiation detector 1 recorded in the detector data and the flight distance. For example, if an object exists at a position shorter than the flight distance, the parallel computing unit 36 ​​determines that the photon is incident on an object. For example, if no object is present before the photon consumes its entire flight distance, the parallel computing unit 36 ​​determines that the photon is not incident on any object.

[0059] If the photon does not enter any object inside the radiation detector 1 (S203: NO), the parallel computing unit 36 ​​ends the Monte Carlo ray tracing process and returns the process to the main process executed by the calculation unit 31. If the photon does not enter an object, the photon disappears without being detected. Note that photons do not consume a flight distance in a vacuum. When calculations are performed assuming that the inside of the radiation detector 1 is a vacuum, the parallel computing unit 36 ​​performs calculations assuming that the photon will always enter some object.

[0060] If the photon is incident on an object within the radiation detector 1 (S203: YES), the parallel computing unit 36 ​​determines whether the photon passes through the object (S204). The parallel computing unit 36 ​​identifies the object on which the photon is incident based on the position of each object within the radiation detector 1. In S204, the parallel computing unit 36 ​​compares the distance traveled by the photon within the object with the size of the object. If μ is the absorption coefficient of the object, the distance traveled by the photon within the object becomes shorter as μ increases, and becomes longer as μ decreases. The parallel computing unit 36 ​​calculates the distance traveled by the photon within the object by using the absorption coefficient of the object recorded in the detector data and correcting the flight distance, which is the distance traveled by the photon until it enters the object, according to μ. The parallel computing unit 36 ​​may calculate the distance traveled by the photon within the object using the density of the object.

[0061] The parallel computing unit 36 ​​compares the distance traveled by the photon within the object with the length of the object along the direction of travel of the photon. The length of the object along the direction of travel of the photon is calculated from the position and size of the object recorded in the detector data. The parallel computing unit 36 ​​determines that the photon has passed through the object if the distance traveled by the photon within the object exceeds the length of the object along the direction of travel of the photon. The parallel computing unit 36 ​​determines that the photon has not passed through the object if the distance traveled by the photon within the object does not exceed the length of the object along the direction of travel of the photon.

[0062] If the photon passes through the object (S204: YES), the parallel computing unit 36 ​​corrects the flight distance of the photon (S205). In S205, the parallel computing unit 36 ​​calculates the flight distance consumed by the photon within the object by correcting the length of the object along the flight direction of the photon according to μ. The parallel computing unit 36 ​​corrects the flight distance of the photon by subtracting from the flight distance of the photon the flight distance consumed by the photon before it enters the object and the flight distance consumed by the photon within the object. The parallel computing unit 36 ​​also calculates the position of the photon that has passed through the object. The parallel computing unit 36 ​​then returns the process to S203.

[0063] If the photon does not pass through the object (S204: NO), the parallel computing unit 36 ​​determines whether photoelectric absorption occurs (S206). If the photon does not pass through the object, the photon interacts with the object on which the photon is incident. The parallel computing unit 36 ​​identifies the object on which the photon is incident as an object that interacts with the photon, and calculates the position at which the photon interacts with the object. At this time, the parallel computing unit 36 ​​calculates the position from the position at which the photon is incident on the object along the direction of travel of the photon by the distance the photon travels within the object. The probability that photoelectric absorption occurs within the object is determined by the material of the object and the energy of the photon. In S206, the parallel computing unit 36 ​​calculates the probability of photoelectric absorption occurring depending on the material of the object and the energy of the photon, and probabilistically determines whether photoelectric absorption occurs.

[0064] If photoelectric absorption occurs (S206: YES), the parallel computing unit 36 ​​determines whether fluorescence occurs when photoelectric absorption occurs (S207). Fluorescence occurs when an electron contained in an atom in an object is ejected by a photon, the ejected electron's orbit becomes vacant, and an outer electron transitions to the vacant orbit. For example, fluorescence is fluorescent X-rays. The probability of fluorescence occurrence is determined according to the material and shape of the object, and is stored in advance in the storage unit 34. In S207, the parallel computing unit 36 ​​probabilistically determines whether fluorescence occurs.

[0065] If no fluorescence is generated (S207: NO), the parallel computing unit 36 ​​determines whether or not the object that interacts with the photon is within the sensitive region 117 of the radiation detection element 11 (S208). In S208, the parallel computing unit 36 ​​determines whether or not the position at which the photon interacts with the object is within the sensitive region 117 of the radiation detection element 11.

[0066] If the object that interacts with the photons is not the sensitive region 117 of the radiation detection element 11 (S208: NO), the parallel computing unit 36 ​​ends the Monte Carlo ray tracing process and returns the process to the main process executed by the calculation unit 31. Even if photoelectric absorption occurs, if the object that interacts with the photons is not the sensitive region 117 of the radiation detection element 11, the photons will not be detected.

[0067] If the object interacting with the photons is the sensitive region 117 of the radiation detection element 11 (S208: YES), the parallel computing unit 36 ​​calculates the energy of electrons and holes generated by photoelectric absorption (S209). Photon energy is not necessarily converted entirely into electron and hole energy by photoelectric absorption. Conversion probabilities are determined for different rates of photon energy conversion into electron and hole energy, and these probabilities are pre-stored in the storage unit 34. In S209, the parallel computing unit 36 ​​probabilistically calculates the energy of electrons and holes generated by photoelectric absorption. Furthermore, the energy of electrons detectable by the radiation detection element 11 is affected by the structure of the radiation detection element 11 and the position within the radiation detection element 11 where the photon interacts with the radiation detection element 11. For example, the rate at which generated electrons flow into the signal output electrode 115 differs between positions close to the electrode and positions far from the electrode, resulting in changes in the detected energy. In S209, the parallel computing unit 36 ​​calculates the energy, taking into account the influence of the structure of the radiation detection element 11 and the position where the interaction takes place within the radiation detection element 11.

[0068] The parallel computing unit 36 ​​corrects the energy due to the recombination of electrons and holes (S210). Some of the electrons and holes generated by photoelectric absorption may recombine. The energy of the electrons and holes decreases due to recombination. The probability of recombination occurring is fixed and pre-stored in the storage unit 34. In S210, the parallel computing unit 36 ​​probabilistically calculates the energy decrease and subtracts the calculated energy from the energy calculated in S209, thereby correcting the energy of the electrons and holes.

[0069] The parallel computing unit 36 ​​determines the energy detected by the radiation detector 1 (S211). In S211, the parallel computing unit 36 ​​determines the detected energy according to the corrected electron energy. For example, the parallel computing unit 36 ​​sets the corrected electron energy as the detected energy. For example, the parallel computing unit 36 ​​calculates the detected energy by multiplying the corrected electron energy by a predetermined proportionality coefficient. After S211 is completed, the parallel computing unit 36 ​​ends the Monte Carlo ray tracing process and returns the process to the main process executed by the calculation unit 31.

[0070] If fluorescence is generated in S207 (S207: YES), the parallel computing unit 36 ​​selects a trajectory of the electron ejected by the photon (S212). In S212, the parallel computing unit 36 ​​selects a trajectory probabilistically. The probability of selecting a trajectory depends on the material of the object. If fluorescence is generated, the energy required to eject the electron is reduced from the photon energy, and the photon energy consumed by photoelectric absorption is reduced.

[0071] The parallel computing unit 36 ​​calculates the photon energy consumed by photoelectric absorption and the fluorescence energy (S213). The photon energy consumed by photoelectric absorption is calculated by subtracting the energy required to eject the electron from the original photon energy. The energy required to eject the electron is determined depending on the material of the object. The fluorescence energy is determined depending on the material of the object and also depending on the difference between the orbit of the electron ejected by the photon and the orbit of the electron transitioning to the vacant orbit.

[0072] The parallel computing unit 36 ​​calculates the energy detected in response to the photoelectric absorption (S214). In S214, the parallel computing unit 36 ​​executes the same processes as S208 to S211 for calculating the energy detected in response to the photoelectric absorption.

[0073] The parallel computing unit 36 ​​then corrects the energy of the fluorescence due to Auger electrons (S215). When fluorescence is generated, Auger electrons may be generated, and the energy of the fluorescence decreases in response to the generation of Auger electrons. In S215, the parallel computing unit 36 ​​probabilistically calculates the energy that decreases in response to the generation of Auger electrons, and corrects the fluorescence energy by subtracting the calculated energy from the fluorescence energy. The parallel computing unit 36 ​​determines the position at which the photon interacts with the object as the position of the photon generated by the generation of fluorescence.

[0074] The parallel computing unit 36 ​​calculates the traveling direction of the photons generated by the generation of fluorescence (S216). The traveling direction of the photons generated by the generation of fluorescence does not depend on the angle, and the photons can travel equally in any direction. In S216, the parallel computing unit 36 ​​probabilistically calculates the traveling direction of the photons. After S216 is completed, the parallel computing unit 36 ​​returns the process to S202. In S202, the parallel computing unit 36 ​​calculates the flight distance of the photons generated by the generation of fluorescence.

[0075] If photoelectric absorption does not occur in S206 (S206: NO), the parallel computing unit 36 ​​determines whether inelastic scattering of photons occurs within the object (S217). In S217, the parallel computing unit 36 ​​probabilistically calculates whether inelastic scattering occurs. Inelastic scattering is Compton scattering, which occurs between photons and electrons within the object. In Compton scattering, part of the photon's energy is transferred to the electron, resulting in a decrease in the photon's energy.

[0076] If inelastic scattering occurs (S217: YES), the parallel computing unit 36 ​​calculates the photon energy and electron energy after Compton scattering (S218). In S218, the parallel computing unit 36 ​​probabilistically calculates the energy imparted from the photon to the electron, sets the calculated energy as the electron energy, and calculates the photon energy after Compton scattering by subtracting the electron energy from the original photon energy.

[0077] The parallel computing unit 36 ​​calculates the detected energy of the electrons that have been given energy by Compton scattering (S219). The electrons that have been given energy by Compton scattering in the sensitive region 117 of the radiation detector 1 flow into the signal output electrode 115 and can be detected. In S219, the parallel computing unit 36 ​​executes processing equivalent to S208 to S211 for calculating the energy detected when the electrons are detected. The parallel computing unit 36 ​​determines the position where the photon interacts with the object as the position of the photon after Compton scattering.

[0078] The parallel computing unit 36 ​​then calculates the traveling direction of the photon after Compton scattering (S220). The scattering angle of the photon due to Compton scattering is angle-dependent, and the probability distribution of the scattering angle is expressed by the Klein-Nishina formula. In S220, the parallel computing unit 36 ​​uses the Klein-Nishina formula to probabilistically calculate the traveling direction of the photon. After S220 is completed, the parallel computing unit 36 ​​returns the process to S202. In S202, the parallel computing unit 36 ​​calculates the flight distance of the photon after Compton scattering.

[0079] If inelastic scattering does not occur in S217, elastic scattering occurs within the object. Elastic scattering is Rayleigh scattering that occurs between photons and electrons within the object. In Rayleigh scattering, the traveling direction of the photon may change, but the energy of the photon does not change. If inelastic scattering does not occur in S217 (S217: NO), the parallel computing unit 36 ​​calculates the traveling direction of the photon after Rayleigh scattering (S221). The scattering angle of the photon due to Rayleigh scattering is angle-dependent, and if the scattering angle is θ, the probability distribution P(θ) of the scattering angle is expressed as P(θ) = sin 2 The angle is expressed as θ. In S221, the parallel computing unit 36 ​​probabilistically calculates the traveling direction of the photon using an equation for the probability distribution of the scattering angle. The parallel computing unit 36 ​​determines the position where the photon interacts with the object as the position of the photon after Rayleigh scattering. After S221 is completed, the parallel computing unit 36 ​​returns the process to S202. In S202, the parallel computing unit 36 ​​calculates the flight distance of the photon after Rayleigh scattering.

[0080] In the Monte Carlo ray tracing process of S103, the processes of S201 to S221 are executed for each of the multiple photons contained in the radiation. The process of S103 for the multiple photons is executed in parallel by the parallel computing unit 36. More specifically, the parallel computing unit 36 ​​executes the process of S103 for one photon in one thread. The process of S103 calculates the energy detected for the multiple photons. By executing the process of S103 by the parallel computing unit 36, the Monte Carlo ray tracing process for a large number of photons can be executed at high speed. After the process of S103 is completed, the calculation unit 31 stores the energy detected for the multiple photons in the memory 32 or the storage unit 34.

[0081] The analysis unit 3 then determines the time intervals at which the multiple photons whose energies have been calculated are detected (S104). In S104, the calculation unit 31 selects one detected photon and determines whether the time intervals at which the selected photon and other photons are detected are short. Under the assumption that photon detection occurs randomly, the calculation unit 31 probabilistically determines the time intervals at which the selected photon and other photons are detected, and determines that the time interval is short if the determined time interval is less than a predetermined threshold. The threshold is pre-stored in the storage unit 34 or is included in the computer program 341. The calculation unit 31 may also determine that the time interval is short if the determined time interval matches the predetermined threshold. The calculation unit 31 performs the determination of the detected time intervals for multiple combinations of two photons. For example, the calculation unit 31 determines the detected time intervals for combinations of two photons calculated in two adjacent threads of the parallel calculation unit 36. The calculation unit 31 may determine the time intervals at which the photons are detected for combinations of three or more photons.

[0082] The analysis unit 3 replaces multiple photons detected at short time intervals with a single photon (S105). In S105, the calculation unit 31 modifies the energy calculated in S103 by setting the sum of the energies detected for multiple photons determined to be detected at short time intervals as the energy of a single photon. As a result, multiple photons detected at short time intervals are replaced mathematically with a single photon having energy equal to the sum of some or all of the energies of the multiple photons. The process of S105 can reproduce a sum peak contained in the spectrum of radiation. In the process of S106 described below, it becomes possible to generate a virtual spectrum including the sum peak. The processes of S104 and S105 may be executed by the parallel calculation unit 36.

[0083] The analysis unit 3 generates a virtual spectrum of radiation (S106). The calculation unit 31 counts photons for each calculated energy to generate a virtual spectrum that represents the relationship between the detected energy and the number of detected photons. The virtual spectrum is a virtual spectrum of radiation calculated using Monte Carlo ray tracing. The calculation unit 31 stores data representing the virtual spectrum in the memory 32 or the storage unit 34.

[0084] The analysis unit 3 calculates the error between the measured spectrum and the virtual spectrum (S107). In S107, for example, the calculation unit 31 calculates the difference in radiation intensity associated with each energy between the measured spectrum and the virtual spectrum, and calculates the error by summing the squares of the intensity differences across multiple energies. The calculation unit 31 may calculate the error by summing the squares of the intensity differences within a specific energy range, such as a range including a peak with a relatively high intensity. The calculation unit 31 may calculate the error as the difference in intensity for each energy or the square of the intensity difference. The calculation unit 31 may normalize the measured spectrum and the virtual spectrum before calculating the error. By calculating the error, the analysis unit 3 compares the measured spectrum with the virtual spectrum.

[0085] The analysis unit 3 then determines whether a specific condition is satisfied (S108). In S108, the calculation unit 31 determines whether a condition is satisfied that the error calculated in S107 is within a predetermined range. For example, the calculation unit 31 determines whether a condition is satisfied that the error value is less than a predetermined threshold. For example, the calculation unit 31 determines whether a condition is satisfied that the error is less than a threshold at a number of energies exceeding a predetermined number or within a specific energy range. The specific condition may be a condition that the amount of change in error updated by the repeated calculation in S107 is less than a predetermined lower limit. The specific condition may also be a condition that the number of repetitions of the processes of S103 to S109 or the calculation time reaches a predetermined upper limit.

[0086] If the specific condition is not satisfied (S108: NO), the analysis unit 3 modifies the assumed radiation energy or intensity (S109). In S109, for example, the calculation unit 31 modifies the assumed radiation energy value or intensity value. For example, the calculation unit 31 assumes that the radiation contains multiple types of radiation with different energies and modifies the number of types of radiation with different energies. In S109, the user may operate the operation unit 23 to input the modification content of the radiation energy or intensity, and the calculation unit 31 may make the modification according to the input modification content. The calculation unit 31 may also make the modification without using input from the user.

[0087] In S109, the calculation unit 31 corrects the energy or intensity of the radiation so as to reduce the error between the measured spectrum and the virtual spectrum. For example, the calculation unit 31 stores in the memory unit 34 a history of the correction of the radiation energy or intensity and the change in the error, and corrects the radiation energy or intensity so as to reduce the error based on the stored history. After S109 is completed, the analysis unit 3 returns the process to S103. The analysis unit 3 repeats the processes of S103 to S109 until a specific condition is satisfied. By repeating the processes of S103 to S109, the analysis unit 3 corrects the assumed radiation energy and intensity so that the measured spectrum and the virtual spectrum approximately match. If the measured spectrum and the virtual spectrum approximately match, it can be assumed that the assumed radiation energy and intensity approximately match the actual energy and intensity of the detected radiation.

[0088] If the specific condition is satisfied (S108: YES), the analysis unit 3 determines the energy and intensity of the radiation (S110). In S110, the calculation unit 31 determines the corrected energy and intensity of the radiation as the energy and intensity of the detected radiation. The assumed energy and intensity of the radiation are repeatedly corrected through the processes of S103 to S109, and can be assumed to approximately match the actual energy and intensity of the detected radiation. Therefore, the analysis unit 3 can determine the corrected assumed energy and intensity of the radiation as the energy and intensity of the detected radiation. The calculation unit 31 stores the determined energy and intensity of the radiation in the memory unit 34. The calculation unit 31 may display the results of the determination of the radiation energy and intensity on the display unit 24.

[0089] The analysis unit 3 performs elemental analysis of the sample 4 based on the determined energy and intensity of the radiation (S111). Because the radiation detected using the radiation detector 1 is characteristic X-rays generated from the sample 4, the determined energy and intensity of the radiation are the energy and intensity of the characteristic X-rays generated from the sample 4. Qualitative analysis or quantitative analysis of the elements contained in the sample 4 is possible based on the energy and intensity of the characteristic X-rays. In S111, the calculation unit 31 performs qualitative analysis or quantitative analysis of the elements contained in the sample 4 based on the determined energy and intensity of the radiation. The calculation unit 31 stores the results of the elemental analysis in the memory unit 34. The calculation unit 31 may display the results of the elemental analysis on the display unit 24. After S111 is completed, the analysis unit 3 ends the processing.

[0090] As described above in detail, in this embodiment, the analysis unit 3 assumes the energy and intensity of the radiation to be detected, calculates the energy at which individual photons are detected by Monte Carlo ray tracing, and generates a virtual spectrum of the radiation. The analysis unit 3 corrects the assumed energy and intensity of the radiation based on a comparison between the measured spectrum of the radiation and the virtual spectrum. The analysis unit 3 repeatedly corrects the assumed energy and intensity of the radiation and calculates the energy using Monte Carlo ray tracing so as to reduce the error between the measured spectrum and the virtual spectrum. As a result, the assumed energy and intensity of the radiation are corrected so that the measured spectrum and the virtual spectrum approximately match, and the analysis unit 3 can determine the corrected energy and intensity of the radiation as the energy and intensity of the detected radiation. This makes it possible to accurately determine the energy and intensity of the detected radiation. Based on the accurately determined energy and intensity of the radiation, it becomes possible to accurately perform elemental analysis of the sample 4 that generated the radiation.

[0091] In this embodiment, the Monte Carlo ray tracing process is performed using the flight distance of the photon, but the analysis unit 3 may be configured to perform the Monte Carlo ray tracing process without using the flight distance. In this configuration, the parallel computing unit 36 ​​performs the process of tracing the photon by sequentially calculating the interactions between the photon and objects on the flight path of the photon.

[0092] In this embodiment, the analysis unit 3 executes the Monte Carlo ray tracing process of S103 using the parallel calculation unit 36, but the analysis unit 3 may execute the process of S103 without using the parallel calculation unit 36. For example, the analysis unit 3 may execute the Monte Carlo ray tracing process for a plurality of photons through calculations in the calculation unit 31. In this embodiment, the calculation unit includes the calculation unit 31 but does not include the parallel calculation unit 36.

[0093] <Embodiment 2> In embodiment 2, information processing will be described in which the energy and intensity of detected radiation are determined by utilizing the virtual spectrum obtained by the Monte Carlo ray tracing described in embodiment 1. Fig. 10 is a block diagram showing an example of the internal configuration of an analysis unit 3 according to embodiment 2. The configuration of the radiation detection apparatus 100 other than the analysis unit 3 is the same as in embodiment 1. The analysis unit 3 includes a calculation unit 31, a memory 32, a reading unit 33, a storage unit 34, and an interface unit 35. The analysis unit 3 does not necessarily have to include a parallel calculation unit 36. The storage unit 34 stores a computer program 341, and the calculation unit 31 executes information processing in accordance with the computer program 341.

[0094] The storage unit 34 stores first virtual spectrum data that records the relationship between the energy and intensity of the radiation and the first virtual spectrum. As described in the first embodiment, the virtual spectrum of the radiation can be calculated by assuming the energy and intensity of the radiation and performing Monte Carlo ray tracing for each of the multiple photons contained in the radiation. The virtual spectrum calculated by assuming a specific energy and intensity of the radiation and using Monte Carlo ray tracing is referred to as the first virtual spectrum. The first virtual spectrum data records a first virtual spectrum that is associated with a specific energy and intensity of the radiation and calculated based on the energy and intensity.

[0095] The first virtual spectral data includes a plurality of pairs of specific energy and intensity of radiation and first virtual spectra. For example, the first virtual spectral data includes a first virtual spectrum calculated by an information processing device other than the analysis unit 3 using the Monte Carlo ray tracing described in the first embodiment. The first virtual spectral data may include a first virtual spectrum calculated by the analysis unit 3 itself.

[0096] 11 is a flowchart showing an example of the procedure of processing executed by the analysis unit 3 according to embodiment 2. As in S101, the analysis unit 3 acquires the measured spectrum of radiation emitted from the sample 4 (S31). Next, as in S102, the analysis unit 3 assumes the energy and intensity of the detected radiation (S32).

[0097] The analysis unit 3 generates a second virtual spectrum of the radiation based on the assumed energy and intensity of the radiation (S33). In S33, the calculation unit 31 generates the second virtual spectrum by taking the first virtual spectrum recorded in the first virtual spectrum data in association with the assumed energy and intensity as the second virtual spectrum. At this time, the calculation unit 31 reads out the first virtual spectrum to be used as the second virtual spectrum from the first virtual spectrum data.

[0098] If the assumed radiation energy and intensity are expressed as a linear sum of the energies and intensities of multiple radiations recorded in the first virtual spectrum data, the calculation unit 31 generates a second virtual spectrum by calculating the linear sum of the multiple first virtual spectra in S33. The multiple radiation energies and intensities included in the linear sum correspond to the assumed radiation energy and intensity. At this time, the calculation unit 31 reads out, from the first virtual spectrum data, multiple first virtual spectra recorded for the multiple radiation energies and intensities corresponding to the assumed radiation energy and intensity, and calculates the linear sum of the read out multiple first virtual spectra. The calculation unit 31 stores data representing the second virtual spectrum in the memory 32 or the storage unit 34.

[0099] The analysis unit 3 calculates the error between the measured spectrum and the second virtual spectrum (S34). In S34, for example, the calculation unit 31 calculates the error by summing the squares of the differences in intensity of radiation associated with each energy between the measured spectrum and the second virtual spectrum across multiple energies. The calculation unit 31 may calculate the error by summing the squares of the intensity differences within a specific energy range. The calculation unit 31 may calculate the error as the difference in intensity for each energy or the square of the intensity difference. The calculation unit 31 may normalize the measured spectrum and the second virtual spectrum before calculating the error. By calculating the error, the analysis unit 3 compares the measured spectrum with the second virtual spectrum.

[0100] The analysis unit 3 then determines whether a specific condition is satisfied (S35). In S35, the calculation unit 31 determines whether a condition is satisfied that the error calculated in S35 is within a predetermined range. For example, the calculation unit 31 determines whether a condition is satisfied that the error value is less than a predetermined threshold. For example, the calculation unit 31 determines whether a condition is satisfied that the error is less than a threshold for a number of energies exceeding a predetermined number or within a specific energy range. The specific condition may be a condition that the amount of change in the repeatedly updated error is less than a predetermined lower limit. The specific condition may also be a condition that the number of repetitions of the processes of S33 to S36 or the calculation time reaches a predetermined upper limit.

[0101] If the specific condition is not satisfied (S35: NO), the analysis unit 3 modifies the assumed radiation energy or intensity (S36). In S36, for example, the calculation unit 31 modifies the assumed radiation energy value or intensity value. For example, the calculation unit 31 modifies the number of radiation types with different energies. In S36, the user may input the modification of the radiation energy or intensity by operating the operation unit 23. The calculation unit 31 may also perform the modification without using input from the user.

[0102] In S36, the calculation unit 31 corrects the energy or intensity of the radiation so as to reduce the error between the measured spectrum and the second virtual spectrum. The analysis unit 3 repeats the processes of S33 to S36 until a specific condition is met. By repeating the processes of S33 to S36, the analysis unit 3 corrects the assumed energy and intensity of the radiation so that the measured spectrum and the second virtual spectrum approximately match. If the measured spectrum and the second virtual spectrum approximately match, it can be assumed that the assumed energy and intensity of the radiation approximately match the actual energy and intensity of the detected radiation.

[0103] If the specific condition is satisfied (S35: YES), the analysis unit 3 determines the energy and intensity of the radiation (S37). In S37, the calculation unit 31 determines the corrected energy and intensity of the radiation as the energy and intensity of the detected radiation. The calculation unit 31 stores the determined energy and intensity of the radiation in the memory unit 34. The calculation unit 31 may display the determined results of the energy and intensity of the radiation on the display unit 24.

[0104] The analysis unit 3 performs elemental analysis of the sample 4 based on the determined radiation energy and intensity (S38). The calculation unit 31 stores the results of the elemental analysis in the memory unit 34. The calculation unit 31 may display the results of the elemental analysis on the display unit 24. After S38 is completed, the analysis unit 3 ends the processing.

[0105] As described above in detail, in this embodiment, the analysis unit 3 assumes the energy and intensity of the detected radiation, and generates a second virtual spectrum of the detected radiation using a first virtual spectrum corresponding to the assumed energy and intensity of the radiation. The analysis unit 3 corrects the assumed energy and intensity of the radiation based on a comparison between the measured spectrum of the radiation and the second virtual spectrum. The analysis unit 3 repeatedly corrects the assumed energy and intensity of the radiation and generates the second virtual spectrum so as to reduce the error between the measured spectrum and the second virtual spectrum. As a result, the assumed energy and intensity of the radiation are corrected so that the measured spectrum and the second virtual spectrum approximately match, and the analysis unit 3 can determine the corrected energy and intensity of the radiation as the energy and intensity of the detected radiation. This embodiment also makes it possible to accurately determine the energy and intensity of the detected radiation.

[0106] In the first and second embodiments, the radiation detection element 11 is made of a semiconductor such as Si, but the radiation detection element 11 may be made of a semiconductor other than Si. In the first and second embodiments, the radiation detection element 11 is made of a silicon drift type radiation detection element, but the radiation detection element 11 may be made of a semiconductor other than a silicon drift type radiation detection element. Therefore, the radiation detector 1 may be a radiation detector other than an SDD.

[0107] In the first and second embodiments, the radiation detector 1 includes the collimator 13, but the radiation detector 1 may not include the collimator 13. The radiation detector 1 may not include the cold finger 17. In this embodiment, for example, the heat dissipating end of the Peltier element 15 contacts the housing 16 directly or via an intervening material, and heat is dissipated through the housing 16. The radiation detector 1 does not need to be provided with the window 161, and an opening that is not covered by a window material may be formed at the tip of the housing 16. In the first and second embodiments, the radiation detector 1 includes the housing 16, but the radiation detector 1 may not include the housing 16.

[0108] In the first and second embodiments, the radiation detection device 100 is shown to include the irradiation unit 26, but the radiation detection device 100 may be shown to not include the irradiation unit 26. In the first and second embodiments, the radiation detection element 11 made of semiconductor is used, but the radiation detection device 100 may be shown to detect radiation using a radiation detection element other than a semiconductor radiation detection element. In the first and second embodiments, the radiation detection device 100 is shown to handle a spectrum in which the horizontal axis represents the energy of radiation, but the radiation detection device 100 may be shown to handle a spectrum in which the horizontal axis represents the wavelength or wavenumber of radiation.

[0109] In the first and second embodiments, the radiation detection device 100 detects radiation composed of a plurality of photons, but the radiation detection device 100 may also detect radiation composed of a plurality of particles. In this embodiment, the radiation detection device 100 can perform processing in which the photons described in the first and second embodiments are replaced with particles.

[0110] 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 modified appropriately within the scope of the claims are also included in the technical scope of the present invention.

[0111] The matters described in each embodiment can be combined with each other. Furthermore, the independent claims and dependent claims described in the claims can be combined with each other in any and all combinations, regardless of the reference format. Furthermore, the claims use a format in which a claim references two or more other claims (multiple claim format), but this is not limited to this. A multiple claim (multi-multi claim) that references at least one other multiple claim may also be used.

[0112] REFERENCE SIGNS LIST 100 Radiation detection device 1 Radiation detector 11 Radiation detection element 117 Sensitive part 22 Signal processing part 26 Irradiation part 3 Analysis part (information processing device) 30 Recording medium 31 Calculation part 34 Storage part 341 Computer program 36 Parallel calculation part 4 Sample

Claims

1. An information processing method comprising: acquiring a measured spectrum of radiation detected using a radiation detector; assuming the energy and intensity of said radiation; calculating the energy specified when each photon is detected by performing Monte Carlo ray tracing using the assumed energy and intensity for each of a plurality of photons contained in said radiation whose energy and intensity have been assumed; generating a virtual spectrum of said radiation by counting the number of photons for each calculated energy; modifying the assumed energy or intensity in accordance with a comparison between said measured spectrum and said virtual spectrum; and determining the modified energy and intensity as the energy and intensity of said radiation.

2. The information processing method according to claim 1, characterized in that the Monte Carlo ray tracing identifies an object that interacts with each photon, probabilistically determines the type of interaction between each photon and the object, probabilistically calculates the energy or direction of the photon that changes due to the interaction, and calculates the energy of the photon that is detected as a result of the interaction between the photon and a radiation detection element included in the radiation detector.

3. The information processing method according to claim 2, characterized in that the Monte Carlo ray tracing probabilistically calculates the flight distance of each photon, and identifies objects that interact with each photon based on the position and size of each object included in the radiation detector and the flight distance.

4. An information processing method according to any one of claims 1 to 3, characterized in that it probabilistically determines whether the time intervals at which multiple photons whose energies have been calculated are detected are short or not, and corrects the energy calculated using the Monte Carlo ray tracing by adding up the energies of multiple photons whose detection intervals are determined to be short, and setting the sum to the energy of a single photon.

5. An information processing method comprising: storing a first virtual spectrum of radiation calculated by performing Monte Carlo ray tracing on each of a plurality of photons contained in the radiation in association with the energy and intensity of the radiation; acquiring an actual measured spectrum of the radiation detected using a radiation detector; assuming the energy and intensity of the radiation; generating a second virtual spectrum of the radiation based on the first virtual spectrum stored in association with the energy and intensity corresponding to the assumed energy and intensity; modifying the assumed energy or intensity of the radiation in accordance with a comparison between the actual measured spectrum and the second virtual spectrum; and determining the modified energy and intensity as the energy and intensity of the radiation detected using the radiation detector.

6. An information processing method according to any one of claims 1 to 5, characterized in that an actual measured spectrum of radiation emitted from a sample is acquired, and elemental analysis of the sample is performed based on the determined energy and intensity of the radiation.

7. A computer program that causes a computer to perform the following processes: for each of a plurality of photons contained in radiation with assumed energy and intensity, calculate the energy specified when each photon is detected using a radiation detector by performing Monte Carlo ray tracing using the assumed energy and intensity; generate a virtual spectrum of the radiation by counting the number of photons for each calculated energy; modify the assumed energy or intensity in accordance with a comparison between the actual spectrum of the radiation detected using the radiation detector and the virtual spectrum; and determine the modified energy and intensity as the energy and intensity of the radiation detected using the radiation detector.

8. An information processing device comprising a calculation unit which: acquires a measured spectrum of radiation detected using a radiation detector; assumes the energy and intensity of the radiation; calculates the energy specified when each photon is detected by performing Monte Carlo ray tracing using the assumed energy and intensity for each of a plurality of photons contained in the radiation whose energy and intensity have been assumed; generates a virtual spectrum of the radiation by counting the number of photons for each calculated energy; modifies the assumed energy or intensity in accordance with a comparison between the measured spectrum and the virtual spectrum; and determines the modified energy and intensity as the energy and intensity of the radiation.

9. The information processing device according to claim 8, wherein the calculation unit has a parallel calculation unit, and the parallel calculation unit executes in parallel a process of calculating, for each of a plurality of photons, the energy that is identified when each photon is detected by performing the Monte Carlo ray tracing.

10. A radiation detection device comprising: an irradiation unit that irradiates a sample with radiation; a radiation detector that detects radiation from the sample; and the information processing device according to claim 8 or 9.

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