Detection device and radiation identification device

Abstract

To solve a problem in which the other radiations may arrive at a radiation detector and the usefulness of data regarding the other radiations is lower than the usefulness of data of Compton scattering.SOLUTION: A detection device for detecting radiations comprises: a container for housing gas; an electronic detector that is positioned inside the container and generates an analog signal by detecting electrons generated by Compton scattering; a drift electrode that opposes the electronic detector; a radiation detector for generating an analog signal by detecting radiations scattered by Compton scattering; a first read circuit for digitizing the analog signal generated by the radiation detector, generating first data, and storing the first data in a first buffer; and a second read circuit for digitizing the analog signal generated by the electronic detector and generating second data. The first read circuit transmits first final data including the first data stored in the first buffer to an external computer according to a first trigger signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a detection device and a radiation identification device for detecting radiation.

Background Art

[0002] As a device for detecting radiation, for example, as disclosed in Patent Documents 1 to 3, a detection device for detecting Compton-scattered radiation and electrons generated by Compton scattering is known. The detection device includes a container in which a gas is contained, an electron detector for detecting electrons generated by Compton scattering, and a radiation detector for detecting radiation scattered by Compton scattering.

[0003] Data on electrons detected by the electron detector is useful for analyzing radiation. For example, as described in Patent Document 1, information on the scattering direction of radiation is calculated from information on the position of radiation detected by the radiation detector and information on the generation point of electrons.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In addition to the radiation scattered by Compton scattering, other types of radiation may reach the radiation detector. These other types of radiation include radiation that reaches the detector without being scattered inside the container, and radiation that reaches the detector without passing through the container. These other types of radiation do not involve the generation of electrons inside the container. Therefore, analysis of these other types of radiation is more limited than analysis of radiation scattered by Compton scattering. Consequently, the usefulness of data on these other types of radiation is lower than that of data on radiation scattered by Compton scattering.

[0006] The radiation data acquired by the radiation detector is transmitted to the computer. When all the radiation data acquired by the radiation detector is transmitted to the computer, the computer's load becomes heavy.

[0007] The embodiments of this disclosure aim to provide a detection device that can effectively solve such problems. [Means for solving the problem]

[0008] Embodiments of this disclosure relate to the following [1] to

[28] . [1] A detection device for detecting radiation, A container containing gas, An electron detector located inside the aforementioned container, which detects electrons generated by Compton scattering and generates an analog signal, A drift electrode facing the electron detector, A radiation detector that detects radiation scattered by the Compton scattering and generates an analog signal, A first readout circuit that digitizes the analog signal generated by the radiation detector to generate first data and stores the first data in a first buffer, The system includes a second readout circuit that digitizes the analog signal generated by the electron detector to generate second data, The first read circuit is a detection device that transmits the first final data, including the first data stored in the first buffer, to an external computer in response to a first trigger signal.

[0009] [2] In the detection device described in [1], the first final data may include information about the time when the first data was stored in the first buffer.

[0010] [3] In the detection device described in [1] or [2], the radiation detector may include a plurality of detection elements, and the first final data may include information relating to the arrival position of the radiation on the radiation detector.

[0011] In the detection device described in [4] [3], the first final data may include information regarding the intensity of the analog signal generated by the radiation detector.

[0012] [5] In the detection device described in any one of [1] to [4], the first buffer of the first readout circuit stores the first data for a first storage period, the first storage period may be less than or equal to the maximum travel time. The maximum travel time may be the time required for an electron to move from the drift electrode to the electron detector.

[0013] In the detection device described in [6] [5], the maximum travel time may be 10.24 μs or less.

[0014] [7] In the detection device described in any one of [1] to [6], the first trigger signal may be generated in response to the generation of the second data.

[0015] [8] In the detection device according to [7], the detection device may include a logic circuit connected to the first readout circuit and the second readout circuit. The second readout circuit may generate a second hit signal when the intensity of the analog signal of the electron detector exceeds a threshold value. The logic circuit may generate the first trigger signal in response to the generation of the second hit signal.

[0016] [9] In the detection device according to [8], the second readout circuit may include a second buffer for storing the second data. The logic circuit may generate a second trigger signal in response to the generation of the second hit signal. The second readout circuit may transmit second final data including the second data stored in the second buffer to the computer according to the second trigger signal.

[0017]

[10] In the detection device according to [9], the logic circuit may generate the first trigger signal and the second trigger signal simultaneously.

[0018]

[11] In the detection device according to [9] or

[10] , the logic circuit may generate the second trigger signal after a second delay time has elapsed since the second hit signal was generated in the electron detector.

[0019]

[12] In the detection device according to

[11] , the second delay time may be less than or equal to the maximum movement time. The maximum movement time may be the time required for an electron to move from the drift electrode to the electron detector.

[0020]

[13] In the detection device according to

[11] or

[12] , the second buffer of the second readout circuit stores the second data during a second storage period, and the second storage period may be longer than or equal to the second delay time.

[0021]

[14] In the detection device according to any one of [9] to

[13] , the electron detector may include a plurality of anode electrodes and a plurality of cathode electrodes, and the analog signal of the electron detector may include an anode analog signal generated by the plurality of anode electrodes and a cathode analog signal generated by the plurality of cathode electrodes. The second readout circuit may generate an anode hit signal when the intensity of the anode analog signal exceeds a threshold value, and may generate a cathode hit signal when the intensity of the cathode analog signal exceeds a threshold value. The logic circuit may generate the second trigger signal in response to the generation of both the anode hit signal and the cathode hit signal.

[0022]

[15] In the detection device according to any one of [9] to

[14] , the second final data may include information regarding the intensity of the analog signal generated by the electron detector.

[0023]

[16] In the detection device according to

[15] , the second readout circuit may acquire information regarding the intensity of the analog signal generated by the electron detector at a sampling frequency of 50 MHz or less.

[0024]

[17] In the detection device according to

[15] , the second readout circuit may acquire information regarding the intensity of the analog signal generated by the electron detector at a sampling frequency of 10 MHz or more and 20 MHz or less.

[0025]

[18] In the detection device according to any one of [8] to

[17] , the first readout circuit may generate a first hit signal when the intensity of the analog signal of the radiation detector exceeds a threshold value, and the logic circuit may generate the first trigger signal when the second hit signal is generated within a first holding period after the first hit signal is generated.

[0026] In the detection apparatus described in

[19]

[18] , the first maintenance period may be less than or equal to the maximum travel time. The maximum travel time may be the time required for electrons to travel from the drift electrode to the electron detector.

[0027] In the detection device described in any one of

[20] [8] to

[17] , the first readout circuit may generate a first hit signal when the intensity of the analog signal of the radiation detector exceeds a threshold, and the logic circuit may generate the first trigger signal and the second trigger signal if the second hit signal is generated within a first maintenance period after the first hit signal is generated.

[0028]

[21] In the detection device described in any one of [1] to [6], the first readout circuit may generate a first hit signal when the intensity of the analog signal of the radiation detector exceeds a threshold, and the first trigger signal may be generated after a first delay time has elapsed since the first hit signal was generated.

[0029] In the detection device described in

[22]

[21] , the first delay time may be 0.45 times or more and 1.00 times or less the maximum travel time. The maximum travel time may be the time required for an electron to move from the drift electrode to the electron detector.

[0030]

[23] In the detection device described in

[21] or

[22] , the second readout circuit may generate a second hit signal when the intensity of the analog signal of the electron detector exceeds a threshold, and the first trigger signal may be generated if the second hit signal is generated during the first delay time.

[0031]

[24] In the detection device described in any one of [1] to

[23] , the first readout circuit may transmit information regarding the detection delay time in the radiation detector to the computer.

[0032] In the detection device described in

[25]

[24] , the detection delay time may be calculated based on the intensity of the analog signal generated by the electron detector.

[0033]

[26] A radiation-specific device, A detection device described in any one of [1] to

[25] , The system comprises a computer that receives the first final data and the second final data transmitted by the detection device, The computer is a radiation identification device that calculates the direction of incidence of radiation to the detection device based on the first final data and the second final data.

[0034]

[27] A radiation-specific device, A detection device described in any one of [1] to

[25] , The system comprises a computer that receives the first final data and the second final data transmitted by the detection device, The computer is a radiation identification device that images the location of radiation-emitting sources based on the first final data and the second final data.

[0035]

[28] A radiation-specific device, The detection device described in

[24] or

[25] , The system includes a computer that receives the first final data, the second final data, and information regarding the detection delay time transmitted by the detection device, A radiation identification device in which the computer identifies the coordinates of electrons generated by Compton scattering based on the first final data, the second final data, and the information regarding the detection delay time.

[0036] According to embodiments of this disclosure, the amount of radiation-related data transmitted to a computer can be reduced. [Brief explanation of the drawing]

[0037] [Figure 1] This is a cross-sectional view showing an example of a detection device. [Figure 2] This is a perspective view showing an example of an electron detector. [Figure 3] This is a cross-sectional view showing an example of an electron detector. [Figure 4] This is a perspective view showing an example of a radiation detector. [Figure 5] This figure shows an example of Compton scattering occurring in a detection device. [Figure 6] This diagram shows how electrons reach an electron detector. [Figure 7] This figure shows examples of analog signals generated by a radiation detector and analog signals generated by an electron detector. [Figure 8] This figure shows an example of a circuit for generating data. [Figure 9] This figure shows an example of a second readout circuit and logic circuit. [Figure 10] This figure shows an example of an anode readout circuit. [Figure 11] This figure shows an example of the first readout circuit. [Figure 12] This figure shows an example of signal processing. [Figure 13] This figure shows examples of the first and second final data transmitted to the computer. [Figure 14] This figure shows an example of signal processing. [Figure 15] This figure shows an example of signal processing in the first modified example. [Figure 16] This figure shows the second readout circuit and logic circuit in the second modified example. [Figure 17] This figure shows the signal processing in the second modified example. [Figure 18] This is a perspective view showing the electron detector in the third modified example. [Figure 19] This figure shows an example of the second readout circuit and logic circuit in a third modified example. [Figure 20] This figure shows the first read circuit, the second read circuit, and the logic circuit in the fourth modified example. [Figure 21]This figure shows the signal processing in the fourth modified example. [Figure 22] This diagram shows the configuration of a device for measuring maximum travel time. [Figure 23] This graph shows the number of electrons detected by the apparatus in Figure 22. [Figure 24] This figure shows the analog signal in the fifth modified example. [Figure 25] This figure shows the signal processing in the sixth modified example. [Figure 26] This figure shows the signal processing in the sixth modified example. [Modes for carrying out the invention]

[0038] The embodiments described below are examples of embodiments of the present disclosure, and the present disclosure is not construed to be limited to these embodiments. Furthermore, in this specification, terms such as “substrate,” “base material,” “sheet,” and “film” are not distinguished from each other solely on the basis of differences in designation. For example, “substrate” and “base material” are concepts that also include components that may be called sheets or films. Moreover, terms used in this specification to specify shape, geometric conditions, and their degree, such as “parallel” and “orthogonal,” as well as values ​​of length and angle, are not bound by strict meaning, but are interpreted to include a range that can be expected to have similar functions.

[0039] In the drawings referenced herein, identical or similar parts are denoted by the same or similar reference numerals, and repeated descriptions may be omitted. Furthermore, the dimensional ratios in the drawings may differ from the actual ratios for illustrative purposes, and some components may be omitted from the drawings.

[0040] In this specification, if multiple candidate upper limits and multiple candidate lower limits are given for a certain parameter, the numerical range of that parameter may be constructed by combining any one candidate upper limit and any one candidate lower limit. For example, consider the case where it is stated that "Parameter B is, for example, A1 or greater, and may be A2 or greater, and may be A3 or greater. Parameter B is, for example, A4 or less, and may be A5 or less, and may be A6 or less." In this case, the numerical range of parameter B may be A1 or greater and A4 or less, A1 or greater and A5 or less, A1 or greater and A6 or less, A2 or greater and A4 or less, A2 or greater and A5 or less, A2 or greater and A6 or less, A3 or greater and A4 or less, A3 or greater and A5 or less, and A3 or greater and A6 or less.

[0041] The configuration of the detection device 10 according to the embodiment of this disclosure will be described in detail below with reference to the drawings. First, an overview of the detection device 10 will be described. Figure 1 is a cross-sectional view showing an example of the detection device 10.

[0042] (Detection device) The detection device 10 comprises a container 20, an electron detector 30 and a drift electrode 40 located inside the container 20, and a radiation detector 50. The container 20 is, for example, a chamber. The container 20 contains at least a noble gas such as argon or xenon. In addition to the noble gas, the container 20 may also contain a quenching gas with quenching properties such as carbon dioxide or methane.

[0043] The container 20 includes a first section 21, a second section 22 facing the first section 21 in a first direction D1, and a side section 23 extending from the first section 21 toward the second section 22. The detection device 10 may be used to detect radiation incident into the interior of the container 20 through the first section 21. As shown in Figure 1, the container 20 may have a cylindrical shape; that is, the side section 23 may have a circular cross-section. Although not shown, the container 20 may have a shape other than cylindrical, such as a cube or a rectangular parallelepiped. The first section 21 may be curved so as to be convex toward the outside of the container 20. The container 20 may include a corner 24 located between the first section 21 and the side section 23. The first section 21 may extend flat. The corner 24 may include a surface extending in a direction different from that of the first section 21 and the side section 23.

[0044] The object that emits radiation is located outside the container 20. Part 1 21 may include the surface of the container 20 that is closest to the object.

[0045] It is preferable that the material of the container 20 is easily permeable to radiation. This suppresses the absorption or scattering of radiation by the container 20 as it passes through it. The container 20 may include, for example, plastic or metal. The plastic may be fiber-reinforced plastic. If metal is used, the container 20 may be composed of a single metal element or an alloy. As the metal, for example, aluminum or aluminum alloy can be used. To reduce the weight of the container 20, a metal with a specific gravity of less than 4 may be used.

[0046] If the container 20 contains plastic, the thickness of the container 20 may be, for example, 1 mm or more, 5 mm or more, or 10 mm or more. The thickness of the container 20 may be, for example, 30 mm or less, 25 mm or less, or 20 mm or less.

[0047] If the container 20 contains metal, the thickness of the container 20 may be, for example, 2 mm or more, 3 mm or more, or 5 mm or more. The thickness of the container 20 may be, for example, 20 mm or less, 15 mm or less, or 10 mm or less.

[0048] The drift electrode 40, electron detector 30, and radiation detector 50 are arranged in this order on the side moving from the first part 21 to the second part 22. That is, the drift electrode 40 is located on the side of the first part 21 than the electron detector 30. The radiation detector 50 is located on the side of the second part 22 than the electron detector 30. "Component A is located on the side of the first part 21 than component B" means that component A is located on the side indicated by arrow S1 in Figure 1 relative to component B. Arrow S1 represents the direction from the second part 22 to the first part 21. The distance from component B to the first part 21 may be longer or shorter than the distance from component B to component A.

[0049] The drift electrode 40 may be closer to the first part 21 than to the second part 22. The electron detector 30 and the radiation detector 50 may be closer to the second part 22 than to the first part 21.

[0050] The radiation detector 50 may be located outside the container 20. For example, the radiation detector 50 may be located outside the second part 22. The radiation detector 50 may be facing the drift electrode 40 across the second part 22.

[0051] Although not shown in the diagram, the radiation detector 50 may be located inside the container 20. For example, the radiation detector 50 may be located between the second part 22 and the electron detector 30.

[0052] The electron detector 30, the drift electrode 40, and the radiation detector 50 will be described in detail.

[0053] When radiation incident inside container 20 collides with the gas, Compton scattering may occur. Compton scattering generates recoil electrons. Ionizing electrons are also generated along the tracks of these recoil electrons. The electron detector 30 detects these ionizing electrons. By detecting these ionizing electrons, the tracks and energies of the recoil electrons can be calculated.

[0054] Figure 2 is a perspective view showing an example of an electron detector 30. The electron detector 30 includes multiple electrodes. Electrons generated by Compton scattering reach some of the electrodes. Some of the electrodes generate an analog signal upon arrival of the electrons. By identifying the electrodes that generated the analog signal, information about the electron's arrival position on the electron detector 30 can be obtained. Based on the intensity of the analog signal, information about the energy of the electron that reached the electron detector 30 can be obtained. The intensity of the analog signal is calculated based on the voltage, amplitude, etc., of the analog signal. For example, the voltage or amplitude of the analog signal may be used as the intensity of the analog signal.

[0055] The electron detector 30 may include a plurality of anode electrodes 31, a plurality of cathode electrodes 32, and a substrate 35. The substrate 35 includes a first surface 351 and a second surface 352 extending in a direction intersecting the first direction D1. The first surface 351 faces the drift electrode 40. The second surface 352 is located on the opposite side of the first surface 351.

[0056] Multiple cathode electrodes 32 may be located on the first surface 351. Multiple cathode electrodes 32 may be arranged in a second direction D2 perpendicular to the first direction D1. Each cathode electrode 32 may extend in a third direction D3 perpendicular to the first direction D1 and the second direction D2.

[0057] The multiple anode electrodes 31 may include multiple line portions 311 located on the second surface 352 and aligned in the third direction D3. Each line portion 311 may extend in the second direction D2. Figure 3 is a cross-sectional view showing an example of an electron detector 30. Each line portion 311 may be connected to multiple through portions 312 aligned in the second direction D2 and penetrating the substrate 35. The surface of the through portions 312 may be located in an opening 33 formed in the cathode electrode 32.

[0058] Electrons generated by Compton scattering reach some of the multiple anode electrodes 31 and some of the multiple cathode electrodes 32. Some of the anode electrodes 31 generate an anode analog signal upon arrival of electrons. By identifying the some anode electrodes 31 that generated the anode analog signal, information regarding the position of the electrons that reached the electron detector 30 in the third direction D3 can be obtained. Some of the cathode electrodes 32 generate a cathode analog signal upon arrival of electrons. By identifying the some cathode electrodes 32 that generated the cathode analog signal, information regarding the position of the electrons that reached the electron detector 30 in the second direction D2 can be obtained. In this way, the electron detector 30 shown in Figures 2 and 3 can efficiently provide information regarding the position of electrons that reached the electron detector 30 in the second direction D2 and the third direction D3.

[0059] The electron detector 30 may be provided with a second readout circuit 130, which will be described later, for processing analog signals. The second readout circuit 130 may be provided on a component separate from the electron detector 30. In this case, the electron detector 30 may be provided with a cable, a hermetic connector, and a wiring board for transmitting analog signals to the second readout circuit 130.

[0060] The drift electrode 40 is positioned to face the electron detector 30. For example, the drift electrode 40 faces the electron detector 30 in a first direction D1. In this case, the drift electrode 40 includes a plane extending in a direction perpendicular to the first direction D1. An electric field is generated between the electron detector 30 and the drift electrode 40, with the electric field directed from the electron detector 30 to the drift electrode 40. Ionized electrons associated with recoil electrons generated by Compton scattering are attracted towards the electron detector 30 by the electric field.

[0061] The radiation detector 50 detects scattered radiation. In this embodiment, radiation scattered between the electron detector 30 and the drift electrode 40 is detected by the radiation detector 50 after passing through the electron detector 30 and the second part 22 of the container. The radiation detector 50 can detect the position and energy of the radiation that reaches it.

[0062] Figure 4 is a perspective view showing an example of a radiation detector 50. The radiation detector 50 may include a plurality of detection elements 51 and a circuit board 52 that supports the detection elements 51. The plurality of detection elements 51 may be arranged in a direction intersecting the first direction D1. For example, the plurality of detection elements 51 may be arranged in a second direction D2 and a third direction D3 that are orthogonal to the first direction D1.

[0063] The radiation reaches some of the multiple detection elements 51. Some of the detection elements 51 generate an analog signal upon arrival of the radiation. By identifying the detection elements 51 that generated the analog signal, information about the location where the radiation arrived on the radiation detector 50 can be obtained. Based on the intensity of the analog signal, information about the energy of the radiation that reached the radiation detector 50 can be obtained. The intensity of the analog signal is calculated based on the voltage, amplitude, etc., of the analog signal.

[0064] The configuration of the detection element 51 is arbitrary, as long as it can detect radiation. For example, the detection element 51 may include a scintillator that is excited by scattered radiation and emits fluorescence, and a photodetector that detects fluorescence. The photodetector may include, for example, an avalanche photodiode. The detection element 51 may include a semiconductor detection element for detecting the scattered radiation. The semiconductor detection element may comprise, for example, a semiconductor containing zinc cadmium telluride.

[0065] The radiation detector 50 may include a first detection element 51 capable of detecting radiation having energy within a first range, and a second detection element 51 capable of detecting radiation having energy within a second range different from the first range. This expands the range of radiation energy that the radiation detector 50 can detect.

[0066] The radiation detected by the detection element 51 is processed as an electrical signal by the circuit board 52. The circuit board 52 may include circuits, wiring, etc., for processing the electrical signal. The electrical signal may be transmitted to the outside of the container 20 via, for example, a cable, hermetic connector, wiring board, etc. (not shown) connected to the circuit board 52.

[0067] Other components of the detection device 10 will be described below.

[0068] As shown in Figure 1, the detection device 10 may include an auxiliary drift electrode 70 located between the electron detector 30 and the drift electrode 40. The auxiliary drift electrode 70 is provided to improve the uniformity of the electric field distribution between the electron detector 30 and the drift electrode 40.

[0069] The auxiliary drift electrode 70 may include a plurality of ring electrodes 72. The plurality of ring electrodes 72 are arranged along the direction in which the electron detector 30 and the drift electrode 40 face each other. The ring electrode 72 includes a first ring surface 73 facing the drift electrode 40 and a second ring surface 74 located on the opposite side of the first ring surface 73.

[0070] An opening 721 may be formed in the ring electrode 72. The opening 721 overlaps with the electron detector 30 in the opposing direction. The ring electrode 72 does not have to overlap with the electron detector 30 in the opposing direction. The ring electrode 72 may overlap with the drift electrode 40 in the opposing direction.

[0071] The auxiliary drift electrode 70 may include a spacer 75 positioned between two adjacent ring electrodes 72 in the opposing direction. The spacer 75 determines the distance between two adjacent ring electrodes 72 in the opposing direction. The distance is determined according to the number of ring electrodes 72, the voltage between the electron detector 30 and the drift electrode 40, etc.

[0072] The drift electrode 40 may be attached to an auxiliary drift electrode 70. For example, the auxiliary drift electrode 70 may include a spacer 75 positioned between the drift electrode 40 and the ring electrode 72. The structure including the drift electrode 40 and the multiple ring electrodes 72 is also referred to as a drift cage 45.

[0073] The auxiliary drift electrode 70 may include wiring 76 that electrically connects two adjacent ring electrodes 72 in the opposing direction. The auxiliary drift electrode 70 may include wiring 76 that electrically connects an adjacent drift electrode 40 and a ring electrode 72 in the opposing direction. The auxiliary drift electrode 70 may include a resistor 77 inserted in the path of the wiring 76. By electrically connecting two adjacent ring electrodes 72, the voltage between the two ring electrodes 72 can be adjusted. This makes it possible to change the potential of ring electrodes 72 aligned in the opposing direction in steps. For example, suppose the potential of the drift electrode 40 is -4000V, the potential of the electron detector 30 is 0V, and 20 ring electrodes 72 are placed between the drift electrode 40 and the electron detector 30. In this case, the potential of the multiple ring electrodes 72 aligned from the drift electrode 40 toward the electron detector 30 can be changed in steps such as -3800V, -3600V, -3400V, ... This makes it possible to improve the uniformity of the electric field formed in the space between the drift electrode 40 and the electron detector 30.

[0074] As shown in Figure 1, the auxiliary drift electrode 70 may be supported by a relay substrate 90. The relay substrate 90 may support the electron detector 30. For example, the relay substrate 90 may include a first substrate 91 that supports the electron detector 30 and a second substrate 92 that supports the auxiliary drift electrode 70. The second substrate 92 may be located between the first substrate 91 and the auxiliary drift electrode 70.

[0075] As shown in Figure 1, the detection device 10 may include an electron amplifier 60 located between the electron detector 30 and the drift electrode 40. The electron amplifier 60 is positioned, for example, to face the electron detector 30 and the drift electrode 40 in a first direction D1.

[0076] The electron amplifier 60 is configured to produce electron avalanche amplification. The electron amplifier 60 includes an electrode having a potential higher than the potential of the drift electrode 40. The electron amplifier 60 may include a plurality of through holes 61 that penetrate through the electron amplifier 60. The electron amplifier 60 may be configured to generate an electric field directed toward the drift electrode 40 in the through holes 61.

[0077] Next, Compton scattering occurring in the detection device 10 will be described. Figure 5 shows an example of Compton scattering. The symbol R1 represents radiation that has passed through the first part 21 of the container 20 and entered the interior of the container 20. Radiation R1 can be, for example, charged particle beams (e.g., alpha rays, beta rays, etc.), uncharged particle beams (e.g., neutral particles, neutron beams, etc.), electromagnetic waves (e.g., gamma rays, X-rays, etc.), or non-ionizing radiation (e.g., ultraviolet light, etc.). After passing through the drift electrode 40, radiation R1 reaches the space between the electron detector 30 and the drift electrode 40.

[0078] When radiation R1 collides with the gas, Compton scattering may occur. The symbol P represents the location where scattering occurs. Location P is also called the scattering point. The symbol R2 represents the scattered radiation. After passing through the electron detector 30, radiation R2 reaches the radiation detector 50. If the radiation detector 50 is located outside the container 20, radiation R2 also passes through the second part 22 of the container 20. Radiation R2 is detected by some of the detection elements 51 among the multiple detection elements 51. For example, radiation R2 is detected by one detection element 51. This allows us to calculate the arrival location and energy of radiation R2.

[0079] Compton scattering generates recoil electrons. The symbol R3 indicates the electron cloud formed in the tracks of the recoil electrons. The symbol e1 represents the electron located at the starting point of the electron cloud R3. Electron e1 may also be located at the scattering point P. The symbol e2 represents the electron located at the ending point of the electron cloud R3.

[0080] Each electron in the electron cloud R3 moves toward the electron detector 30 due to the electric field E1. This movement is also called drift. Each electron in the electron cloud R3 that reaches the electron detector 30 is detected by the anode electrode 31 and cathode electrode 32 of the electron detector 30. This allows the position and energy of each electron in the electron cloud R3 to be calculated. In addition, the trajectory and energy of the recoil electrons, as well as the scattering point P, can be calculated.

[0081] Radiation R2 travels from the scattering point P to the radiation detector 50 at nearly the speed of light. Recoil electrons also travel from the position of electron e1 to the position of electron e2 at nearly the speed of light. On the other hand, the velocity V at which the electron cloud R3 moves toward the electron detector 30 is slower than the speed of light. Therefore, each electron in the electron cloud R3 reaches the electron detector 30 after radiation R2 has reached the radiation detector 50. The time it takes for each electron in the electron cloud R3 to reach the electron detector 30 varies depending on the distance from each electron to the electron detector 30. In the example shown in Figure 6, the distance from electron e2 to the electron detector 30 is shorter than the distance from electron e1 to the electron detector 30. Therefore, electron e2 reaches the electron detector 30 before electron e1.

[0082] In Figure 6, the signs t0, t1, and t2 enclosed in square frames represent the time when electrons from radiation R2 or electron cloud R3 are generated or arrive at the positions indicated by the signs. Ignoring the time required for the movement of radiation R2 and recoil electrons, the time when electron e1 is generated, the time when electron e2 is generated, and the time when radiation R2 reaches the radiation detector 50 are all t0. Electron e1 arrives at the electron detector 30 at time t1, after time t0. Electron e2 arrives at the electron detector 30 at time t2. Time t2 is after time t0, and time t1 is after time t2.

[0083] The radiation detector 50 generates an analog signal when it detects radiation R2. The electron detector 30 generates an analog signal when it detects electrons. Figure 7 shows an example of the analog signal W_R2 generated by the radiation detector 50 and the analog signal W_R3 generated by the electron detector. The analog signal from the radiation detector 50 is generated at time t0. Time ΔT2 is the difference between time t0 and time t2. Time ΔT2 corresponds to the time required for electron e2 to move from the endpoint of electron cloud R3 to electron detector 30. Time ΔT1 is the difference between time t0 and time t1. Time ΔT1 corresponds to the time required for electron e1 to move from the starting point of electron cloud R3 to electron detector 30.

[0084] The longer the distance from the electron cloud R3 to the electron detector 30, the longer the time it takes for electrons to travel to the electron detector 30. The travel time is longest when electrons are generated on the drift electrode 40. The time it takes for electrons to travel from the drift electrode 40 to the electron detector 30 is also called the maximum travel time TMAX. The maximum travel time TMAX is determined based on the distance between the drift electrode 40 and the electron detector 30 (also called the drift length) and the electron drift velocity V. The drift velocity V is determined based on the electric field strength, the type of gas in the container 20, the gas pressure, etc. For example, under conditions 1 and 2 below, the maximum travel time TMAX is 10.24 μs. (Condition 1) Drift length: 40cm, electric field strength: 400V / cm, Gas type: Mixed gas containing argon and ethane; Gas pressure: 1 atmosphere (Condition 2) Drift length: 60cm, electric field strength: 600V / cm, Gas type: Methane tetrafluoride, Gas pressure: 3 atmospheres

[0085] The maximum travel time TMAX is, for example, 3 μs or more, may be 5 μs or more, or 7 μs or more. The maximum travel time TMAX is, for example, 30 μs or less, may be 20 μs or less, or 15 μs or less.

[0086] The maximum travel time TMAX may be measured using an apparatus including an electron detector 30 and a drift electrode 40. Figure 22 shows the configuration of an apparatus for measuring the maximum travel time TMAX. The apparatus comprises a container 20, an electron detector 30 and a drift electrode 40 located inside the container 20, and a radiation source 80 located on the outer surface of a first part 21 of the container 20. The electron detector 30 and the drift electrode 40 are facing each other in a first direction D1 with a distance H between them. The radiation source 80 is a source of radiation. The radiation source 80 is, for example, a standard gamma-ray source (nuclide: Ba-1133, code number: BA402) from the Japan Isotope Association. When Compton scattering occurs inside the container 20 due to radiation from the radiation source 80, recoil electrons are generated and an electron cloud R3 is formed.

[0087] Figure 23 is a graph showing the number of electrons detected by the electron detector 30 of the apparatus shown in Figure 22. The horizontal axis of the graph in Figure 23 represents time. The vertical axis of the graph in Figure 23 represents the number of electrons. Each of the multiple points on the graph in Figure 23 indicates the number of electrons detected at a predetermined sampling frequency. The sampling frequency is, for example, 50 MHz or less. The sampling frequency may be between 10 MHz and 20 MHz.

[0088] As shown in Figure 23, the graph includes a period in which the number of electrons is high and nearly constant. This period corresponds to the maximum migration time TMAX. By identifying the period in which the number of electrons is high and nearly constant, the maximum migration time TMAX can be calculated. The electron drift velocity V is calculated by H / TMAX.

[0089] Next, we will describe a circuit for digitizing the analog signals from the radiation detector 50 and the electron detector 30 to generate data. Figure 8 shows an example of such a circuit.

[0090] The detection device 10 includes at least a first readout circuit 150 and a second readout circuit 130. The first readout circuit 150 and the second readout circuit 130 are capable of communicating with a computer 110. The computer 110 receives digital data transmitted from the first readout circuit 150 and the second readout circuit 130 and processes the digital data. For example, the computer 110 calculates the direction of incidence of radiation onto the container 20 based on the first final data and the second final data, which will be described later. If the dimensions of the detection device 10 are negligible compared to the distance from the radiation-emitting source to the detection device 10, such as with celestial bodies, one incidence direction is identified for one source. In this case, the positional relationship between the incidence direction of radiation and the corresponding source is imaged. On the other hand, if the dimensions of the detection device 10 are not negligible compared to the distance from the radiation-emitting source to the detection device 10, such as with SPECT / PET or BNCT, multiple scattering points are detected for one source, and the incidence direction is identified from each scattering point. In this case, the position where the incident directions identified at each scattering point converge is identified as the position of the radiation source and is imaged. Thus, the combination of the detection device 10 and the computer 110 can function as a radiation identification device that calculates the incident direction of radiation or images the position of the radiation source. The computer 110 may also image the electron cloud generated inside the container 20. In this case, the combination of the detection device 10 and the computer 110 can function as an electron imaging device that images electrons. The computer 110 may be a general-purpose personal computer or a calculation processing module suitable for the detection device 10. SPECT stands for Single Photon Emission Computed Tomography. BNCT stands for Boron Neutron Capture Therapy. PET stands for Positron Emission Tomography.

[0091] The first readout circuit 150 digitizes the analog signal generated by the radiation detector 50 to generate the first data D10. The first data D10 is stored in the first buffer, which will be described later. In response to the input of the first trigger signal TS1, the first readout circuit 150 transmits the first final data FD10 to the computer 110. The first final data FD10 includes the first data D10 stored in the first buffer.

[0092] The second readout circuit 130 digitizes the analog signal generated by the electron detector 30 to generate the second data D20. The second data D20 is stored in the second buffer, which will be described later. In response to the input of the second trigger signal TS2, the second readout circuit 130 transmits the second final data FD20 to the computer 110. The second final data FD20 includes the second data D20 stored in the second buffer.

[0093] As shown in Figure 8, the detection device 10 may include a logic circuit 120 connected to the second read circuit 130. The logic circuit 120 generates a first trigger signal TS1 based on the second data D20 generated by the second read circuit 130, for example. For example, the first trigger signal TS1 is generated in response to the generation of a second hit signal, which will be described later, from the second data D20. The logic circuit 120 may also generate a second trigger signal TS2 based on the second data D20. For example, the second trigger signal TS2 is generated in response to the generation of a second hit signal. The logic circuit 120 may be connected to both the first read circuit 150 and the second read circuit 130. In this case, the logic circuit 120 may generate trigger signals such as the first trigger signal TS1 and the second trigger signal TS2 based on both the first data D10 and the second data D20.

[0094] Figure 9 shows an example of the second read circuit 130 and the logic circuit 120. The second read circuit 130 may include an anode read circuit 131 and a cathode read circuit 132.

[0095] The anode readout circuit 131 digitizes the anode analog signals generated by the multiple anode electrodes 31. The digital data generated by the anode readout circuit 131 is also called the 21st data D21. The 21st data D21 is part of the 2nd data D20. The 21st data D21 may include the 21st hit signal H21. A "hit signal" is a signal generated by binarizing an analog signal. When the intensity of the analog signal exceeds a threshold, the hit signal indicates a High state. When the intensity of the analog signal is below the threshold, the hit signal indicates a Low state. The 21st hit signal H21 is a signal generated by binarizing the anode analog signal. The anode readout circuit 131 may transmit the 21st hit signal H21 to the logic circuit 120.

[0096] As shown in Figure 9, the second readout circuit 130 may include multiple anode readout circuits 131. The number of anode readout circuits 131 is determined according to the number of anode electrodes 31 of the electron detector 30. For example, if there are 256 anode electrodes 31 and one anode readout circuit 131 can process 128 analog signals, the second readout circuit 130 includes two anode readout circuits 131.

[0097] The anode readout circuit 131 may transmit the 21st final data FD21 to the computer 110 in response to the input of the second trigger signal TS2. The 21st final data FD21 includes the 21st data D21. The 21st final data FD21 is part of the second final data FD20.

[0098] The cathode readout circuit 132 digitizes the cathode analog signals generated by the multiple cathode electrodes 32. The digital data generated by the cathode readout circuit 132 is also referred to as the 22nd data D22. The 22nd data D22 is part of the 2nd data D20. The 22nd data D22 may also include the 22nd hit signal H22. The 22nd hit signal H22 is a signal generated by binarizing the cathode analog signal. The cathode electrode 32 may transmit the 22nd hit signal H22 to the logic circuit 120.

[0099] As shown in Figure 9, the second readout circuit 130 may include multiple cathode readout circuits 132. The number of cathode readout circuits 132 is determined according to the number of cathode electrodes 32 of the electron detector 30. For example, if there are 256 cathode electrodes 32 and one cathode readout circuit 132 can process 128 analog signals, the second readout circuit 130 includes two cathode readout circuits 132.

[0100] The cathode readout circuit 132 may transmit the 22nd final data FD22 to the computer 110 in response to the input of the second trigger signal TS2. The 22nd final data FD22 includes the 22nd data D22. The 22nd final data FD22 is part of the second final data FD20.

[0101] The anode readout circuit 131 will be described in detail. Figure 10 shows an example of the configuration of the anode readout circuit 131.

[0102] The anode readout circuit 131 may include a plurality of amplifiers 1361. Each amplifier 1361 amplifies the corresponding anode analog signal AS. The anode readout circuit 131 may include a plurality of comparators 1362. Each comparator 1362 may binarize the anode analog signal AS amplified by the corresponding amplifier 1361 to generate a 21st hit signal h21. The anode readout circuit 131 may include an amplifier 1363. The amplifier 1363 adds up the plurality of anode analog signals AS amplified by the plurality of amplifiers 1361. The intensity of the analog signal output from the amplifier 1363 represents the intensity of electrons detected by the anode electrode 31. For example, the waveform of the analog signal output from the amplifier 1363 represents the waveform of electrons detected by the anode electrode 31. The plurality of amplifiers 1361, the plurality of comparators 1362, and the amplifier 1363 may be composed of the first integrated circuit 136. The first integrated circuit 136 is, for example, an ASIC.

[0103] The anode readout circuit 131 may include an AD converter 137. The AD converter 137 digitizes the analog signal output from the amplifier 1363. The data digitized by the AD converter 137 is also referred to as the 21st intensity data W21. The 21st intensity data W21 is part of the 21st data D21. The AD converter 137 may be a flash-type AD converter. In this case, the analog signal is digitized at high speed. The sampling rate of the AD converter 137 is, for example, 1 MHz or higher, may be 5 MHz or higher, or 10 MHz or higher. The sampling rate of the AD converter 137 is, for example, 50 MHz or lower, may be 30 MHz or lower, or 20 MHz or lower. By setting a low sampling rate, the amount of data generated by the AD converter 137 can be reduced. This reduces the load on the computer 110.

[0104] The anode read circuit 131 may include a 21st buffer 1381 and a 22nd buffer 1382. Buffers included in the second read circuit 130, such as the 21st buffer 1381 and the 22nd buffer 1382, are also referred to as the second buffer.

[0105] The 21st buffer 1381 and the 22nd buffer 1382 are, for example, ring buffers. The 21st buffer 1381 and the 22nd buffer 1382 store the 21st data D21 in themselves during the second storage period. The 21st buffer 1381 may temporarily hold the 21st hit signal h21. The 21st buffer 1381 may temporarily hold the 21st hit signal H21 obtained by processing a plurality of 21st hit signals h21 by an OR circuit. The 21st hit signal H21 indicates a High state if at least one of a plurality of anode analog signals input to the anode readout circuit 131 is in a High state. The 22nd buffer 1382 may temporarily hold the 21st intensity data W21. The second storage period may be less than or equal to the maximum travel time TMAX described above.

[0106] The anode readout circuit 131 may output the 21st hit signal H21 to the logic circuit 120. The anode readout circuit 131 may output the 21st hit signal H21 to the logic circuit 120 before it is stored in the 21st buffer 1381.

[0107] When the second trigger signal TS2 is input to the anode readout circuit 131, the 21st data D21, which is stored in the 21st buffer 1381 and the 22nd buffer 1382 at that time, is output from the 21st buffer 1381 and the 22nd buffer 1382. The anode readout circuit 131 may also include a second data processing unit 1383 that processes the output 21st data D21. The second data processing unit 1383 generates the 21st final data FD21, which is sent to the computer 110.

[0108] The 21st final data includes at least partially the information of the 21st data D21. For example, the 21st final data FD21 may include the information of the 21st hit signal H21. For example, the 21st final data D21 may include the 21st intensity data W21. The format of the information of the 21st data D21 included in the 21st final data FD21 may be the same as or different from the format of the 21st data D21.

[0109] The 21st final data FD21 may include information about the time when the 21st data D21 was stored in the 21st buffer 1381 and the 22nd buffer 1382. The 21st final data FD21 may also include information about the position of the anode electrode 31 that detected the electron. In other words, the 21st final data FD21 may include information about the arrival position of the electron on the electron detector 30.

[0110] The 21st buffer 1381, the 22nd buffer 1382, and the second data processing unit 1383 may be configured by a second integrated circuit 138. The second integrated circuit 138 is, for example, an FPGA.

[0111] The anode readout circuit 131 may output the data acquisition signal DA21 to the logic circuit 120. The data acquisition signal DA21 is a signal that goes high when writing to the 21st buffer 1381 and the 22nd buffer 1382 is taking place.

[0112] The configuration of the cathode readout circuit 132 may be the same as that of the anode readout circuit 131.

[0113] Next, we will refer to Figure 9 again and explain the logic circuit 120.

[0114] If the second readout circuit 130 includes multiple anode readout circuits 131, the logic circuit 120 may include an OR circuit 121, as shown in Figure 9. The 21st hit signal H21 from each anode readout circuit 131 is input to the OR circuit 121. The OR circuit 121 processes the multiple 21st hit signals H21 and outputs a 23rd hit signal H23. The 23rd hit signal H23 indicates a High state if at least one of the multiple 21st hit signals H21 is in a High state. That is, the 23rd hit signal H23 indicates a High state when at least one of the multiple anode analog signals generated by the multiple anode electrodes 31 exceeds a threshold. The 23rd hit signal H23 indicates a Low state if all of the multiple 21st hit signals H21 are in a Low state. That is, the 23rd hit signal H23 indicates a Low state when all of the multiple anode analog signals generated by the multiple anode electrodes 31 are below a threshold. This type of 23rd hit signal, H23, is also called an anode hit signal.

[0115] If the second readout circuit 130 includes multiple cathode readout circuits 132, the logic circuit 120 may include an OR circuit 122, as shown in Figure 9. The 22nd hit signal H22 from each cathode readout circuit 132 is input to the OR circuit 121. The 22nd hit signal H22, like the 21st hit signal H21, indicates a High state if at least one of the multiple cathode analog signals input to the cathode readout circuit 132 is in a High state. The OR circuit 122 processes the multiple 22nd hit signals H22 and outputs a 24th hit signal H24. The 24th hit signal H24 indicates a High state if at least one of the multiple 22nd hit signals H22 is in a High state. That is, the 24th hit signal H24 indicates a High state when at least one of the multiple cathode analog signals generated by the multiple cathode electrodes 32 exceeds a threshold. The 24th hit signal H24 indicates a Low state when all of the multiple 22nd hit signals H22 are in a Low state. In other words, the 24th hit signal H24 indicates a Low state when all of the multiple cathode analog signals generated by the multiple cathode electrodes 32 are below a threshold. Such a 24th hit signal H24 is also called a cathode hit signal.

[0116] If the second readout circuit 130 includes an anode readout circuit 131 and a cathode readout circuit 132, the logic circuit 120 may include an AND circuit 123, as shown in Figure 9. The 23rd hit signal H23 and the 24th hit signal H24 are input to the AND circuit 123. The AND circuit 123 processes the 23rd hit signal H23 and the 24th hit signal H24 to generate the second hit signal H20. The second hit signal H20 indicates a High state when at least one of the multiple anode analog signals from the electron detector 30 exceeds the threshold, and at least one of the multiple cathode analog signals from the electron detector 30 exceeds the threshold. The second hit signal H20 indicates a Low state when all of the multiple anode analog signals are below the threshold, or when all of the multiple cathode analog signals are below the threshold.

[0117] As shown in Figure 9, the logic circuit 120 may include a processing circuit 124 to which the second hit signal H20 is input. When the second hit signal H20 is input to the processing circuit 124, it generates a first trigger signal TS1. The processing circuit 124 may generate the first trigger signal TS1 immediately when the second hit signal H20 is input. Alternatively, the processing circuit 124 may generate the first trigger signal TS1 after a first delay time DT1 has elapsed since the second hit signal H20 was input. The first delay time DT1 may be less than or equal to the maximum travel time TMAX described above.

[0118] The processing circuit 124 may generate the second trigger signal TS2 after a second delay time DT2 has elapsed since the input of the second hit signal H20. The second delay time DT2 may be less than or equal to the maximum travel time TMAX described above. This prevents the generation of the second trigger signal TS2 before electrons generated at a location far from the electron detector 30 reach the electron detector 30.

[0119] Next, the first readout circuit 150 will be described in detail. Figure 11 shows an example of the configuration of the first readout circuit 150. Multiple analog signals ES generated by multiple detection elements 51 of the radiation detector 50 are input to the first readout circuit 150. The first readout circuit 150 digitizes the multiple analog signals ES to generate the first data D10.

[0120] The first readout circuit 150, like the anode readout circuit 131, may include multiple amplifiers for amplifying multiple analog signals ES. The first readout circuit 150, like the anode readout circuit 131, may include multiple comparators for binarizing multiple analog signals ES to generate multiple hit signals. The first readout circuit 150 may process the multiple hit signals with an OR gate to generate a first hit signal H10. The first readout circuit 150 may output the first hit signal H10 to the logic circuit 120. The first hit signal H10 is part of the first data D10. The first hit signal H10 indicates a High state when at least one of the multiple analog signals generated by the multiple detection elements 51 exceeds a threshold. The first hit signal H10 indicates a Low state when all of the multiple analog signals generated by the multiple detection elements 51 are below a threshold.

[0121] The first readout circuit 150 may include an AD converter, similar to the anode readout circuit 131. The AD converter may digitize the analog signal obtained by summing multiple analog signals ES. The data digitized by the AD converter is also referred to as the first intensity data.

[0122] The first read circuit 150 may include a first buffer 1561. The first buffer 1561 is, for example, a ring buffer. The first buffer 1561 stores the first data D10 in itself for a first storage period. The first storage period may be less than or equal to the maximum travel time TMAX described above. If the first trigger signal TS1 is generated after a first delay time DT1 has elapsed since the second hit signal H20 was input, the first storage period may be longer than the maximum travel time TMAX. The first storage period may be shorter than the sum of the first delay time DT1 and the maximum travel time TMAX.

[0123] When the first trigger signal TS1 is input to the first read circuit 150, the first data D10 stored in the first buffer 1561 at that time is output from the first buffer 1561. The first read circuit 150 may also include a first data processing unit 1562 that processes the output first data D10. The first data processing unit 1562 generates the first final data FD1 to be transmitted to the computer 110.

[0124] The first final data FD1 contains at least partially the information of the first data D10. For example, the first final data FD10 may contain information of the first hit signal H10. For example, the first final data D10 may contain first intensity data. The format of the information of the first data D10 included in the first final data FD10 may be the same as or different from the format of the first data D10.

[0125] The first final data FD10 may include information about the time when the first data D10 was stored in the first buffer 1561. The first final data FD10 may also include information about the position of the detection element 51 that detected the radiation. In other words, the first final data FD10 may include information about the arrival position of the radiation on the radiation detector 50.

[0126] The first buffer 1561, the first data processing unit 1562, etc., may be composed of an integrated circuit 156. The integrated circuit 156 is, for example, an FPGA.

[0127] The first read circuit 150 may output the data acquisition signal DA10 to the logic circuit 120. The data acquisition signal DA10 is a signal that goes high when writing to the first buffer 1561 is taking place.

[0128] Next, the logic circuit 120 will be described again with reference to Figure 9. As shown in Figure 9, the VETO signal VS may be input to the processing circuit 124. The VETO signal VS is a signal that goes high when buffer writing is being performed in the anode read circuit 131, cathode read circuit 132, or first read circuit 150. When the VETO signal VS is input to the processing circuit 124, the output of the trigger signals TS1 and TS2 may be stopped. That is, when the VETO signal VS goes high, the processing circuit 124 may set the trigger signals TS1 and TS2 to low. This prevents the input of trigger signals to the anode read circuit 131, cathode read circuit 132, and first read circuit 150 while buffer writing is being performed.

[0129] Next, an example of the operation of the detection device 10 will be described. Figure 12 shows an example of signal processing in the detection device 10.

[0130] When Compton scattering of radiation occurs inside the container 20, recoil electrons and an electron cloud R3 are generated. When the scattered radiation R2 is detected by the radiation detector 50, the first readout circuit 150 generates the first data D10. Figure 12 shows the first hit signal H10 of the first data D10. The first data D10 is stored in the first buffer for the first storage period BT1.

[0131] After radiation R2 is detected by the radiation detector 50, electrons from the electron cloud R3 reach the electron detector 30. When electrons are detected by the anode electrode 31 and the cathode electrode 32, the 21st data D21 and the 22nd data D22 are generated. Figure 12 shows the anode hit signal for the 21st data D21 and the cathode hit signal for the 22nd data D22. The 21st data D21 and the 22nd data D22 are stored in the second buffer for the second storage period BT2.

[0132] When both the anode hit signal and the cathode hit signal are in a high state, a second hit signal is generated. When the second hit signal is generated, a first trigger signal TS1 is generated. When the first trigger signal TS1 is input to the first read circuit 150, the first read circuit 150 transmits the first final data FD10, which includes the first data D10, to the computer 110.

[0133] As shown in Figure 12, the second trigger signal TS2 is generated after a second delay time DT2 has elapsed since the generation of the second hit signal. When the second trigger signal TS2 is input to the second read circuit 130, the second read circuit 130 transmits the second final data FD20, which includes the second data D20, to the computer 110. The second final data FD20 includes the second final data FD21, which includes the 21st data D21, and the 22nd final data FD22, which includes the 22nd data D22.

[0134] In Figure 12, for the first and fifth first data D10 from the left, the first trigger signal TS1 is generated while the first data D10 is stored in the first buffer. Therefore, the first and fifth first data D10 from the left are sent to the computer 110. Figure 13 shows an example of the first final data FD10 and the second final data FD20 sent to the computer 110.

[0135] On the other hand, for the first data D10, the second to fourth from the left in Figure 12, the first trigger signal TS1 is not generated while the first data D10 is stored in the first buffer. This situation can occur when radiation that has not been scattered inside the container 20 reaches the radiation detector 50. This situation can also occur when radiation that has not passed through the container 20 reaches the radiation detector 50. The first data D10, the second to fourth from the left, is erased without being transmitted to the computer 110.

[0136] Figure 14 shows another example of signal processing. In the example shown in Figure 14, the first data D10, which is the first from the left, is accompanied by the generation of the 21st data D21, but not the generation of the 22nd data D22. Therefore, the first trigger signal TS1 is not generated while the first data D10 is stored in the first buffer. This situation can occur when the energy of electrons in the electron cloud R3 is low. When the electron energy is low, it is difficult to accurately calculate the trajectory of recoil electrons, etc. Therefore, the usefulness of the first data D10 and the second data D20 is low when the electron energy is low. The first data D10, which is the first from the left, is erased without being transmitted to the computer 110.

[0137] The computer 110 calculates information about radiation and electrons based on the first final data FD10 and the second final data FD20. For example, the computer 110 may calculate the arrival location of radiation R2, the energy of radiation R2, the trajectory of recoil electrons, the energy of recoil electrons, and the location of the scattering point P. Based on this information, the computer 110 may calculate the incident direction of the radiation incident on the container 20. The computer 110 may also image the position of the radiation source incident on the container 20.

[0138] According to this embodiment, first data D10 relating to radiation that does not involve the proper generation of electrons inside the container 20 is erased without being transmitted to the computer 110. Therefore, the amount of first data D10 transmitted to the computer 110 can be reduced. This reduces the load on the computer 110. For example, the load required for calculation processing, image processing, etc. of the first data D10 is reduced. For example, the load required for communication of the first data D10 is reduced. As a result, the computer 110 can prioritize processing data that is of high usefulness. Therefore, for example, the incident direction of radiation incident on the container 20 can be calculated more quickly than with a conventional computer 110. As a result, for example, when the detection device 10 detects radiation emitted from a radiopharmaceutical inside a patient's body, the degree of exposure to radiation of the patient can be reduced.

[0139] Various modifications can be made to the embodiments described above. Hereinafter, modifications will be described with reference to the drawings as necessary. In the following description and the drawings used therein, parts that can be configured similarly to the embodiments described above will be given the same reference numerals as those used for the corresponding parts in the first embodiment, and redundant explanations will be omitted. Furthermore, if it is clear that the effects and advantages obtained in the embodiments described above can also be obtained in the modifications, the explanation may be omitted.

[0140] (First variation) Figure 15 shows an example of signal processing in the first modified example. As shown in Figure 15, the first trigger signal TS1 and the second trigger signal TS2 may be generated simultaneously in response to the second hit signal. For example, the first delay time DT1 described above may be the same as the second delay time DT2 described above.

[0141] In the example shown in Figure 15, when the first trigger signal TS1 is generated while the first data D10 is stored in the first buffer, the first final data FD10 is sent to the computer 110.

[0142] (Second variation) Figure 16 shows the second readout circuit 130 and logic circuit 120 in a second modified example. As shown in Figure 16, the anode hit signal H23 and the cathode hit signal H24 may be input to the OR circuit 125. The OR circuit 125 processes the 23rd hit signal H23 and the 24th hit signal H24 to generate the second hit signal H20. The second hit signal H20 indicates a High state when at least one of the multiple anode analog signals from the electron detector 30 exceeds a threshold, or at least one of the multiple cathode analog signals from the electron detector 30 exceeds a threshold. The second hit signal H20 indicates a Low state when all of the multiple anode analog signals are below the threshold and all of the multiple cathode analog signals are below the threshold. When the second hit signal H20 is input to the processing circuit 124, it generates the first trigger signal TS1.

[0143] Figure 17 shows an example of signal processing in a second modified example. When an electron is detected by the anode electrode 31 or the cathode electrode 32, the 20th data D20 is generated. Figure 17 shows the second hit signal of the 20th data D20.

[0144] When a second hit signal is generated, a first trigger signal TS1 is generated. When the first trigger signal TS1 is input to the first read circuit 150, the first read circuit 150 transmits the first final data FD10, which includes the first data D10, to the computer 110.

[0145] After the second hit signal is generated and the second delay time DT2 has elapsed, the second trigger signal TS2 is generated. When the second trigger signal TS2 is input to the second read circuit 130, the second read circuit 130 transmits the second final data FD20, which includes the second data D20, to the computer 110.

[0146] In this modified example, the first data D10 relating to radiation that does not involve the generation of electrons inside the container 20 is erased without being transmitted to the computer 110. Therefore, the amount of first data D10 transmitted to the computer 110 can be reduced. This reduces the load on the computer 110. For example, the load required for calculation processing, image processing, etc. of the first data D10 is reduced.

[0147] (Third variation) Figure 18 is a perspective view showing the electron detector 30 in a third modified example. As shown in Figure 18, the electron detector 30 includes a plurality of anode electrodes 31 arranged in a second direction D2 and a third direction D3. The electron detector 30 may also include a single cathode electrode facing the plurality of anode electrodes 31.

[0148] Figure 19 shows an example of the second readout circuit 130 and logic circuit 120 in a third modified example. The second readout circuit 130 includes an anode readout circuit 131 but does not include a cathode readout circuit. In this case, the OR circuit 121 may generate the second hit signal H20. The second hit signal H20 indicates a High state when at least one of the multiple anode analog signals from the electron detector 30 exceeds a threshold. The second hit signal H20 indicates a Low state when all of the multiple anode analog signals are below the threshold.

[0149] An example of signal processing in the third modification is the same as the example of signal processing in the second modification shown in Figure 17. In this modification as well, the first data D10 relating to radiation that does not involve the generation of electrons inside the container 20 is erased without being transmitted to the computer 110. Therefore, the amount of first data D10 transmitted to the computer 110 can be reduced. This reduces the load on the computer 110. For example, the load required for calculation processing and image processing of the first data D10 is reduced.

[0150] (Fourth variation) In this modified example, the first trigger signal TS1 and the second trigger signal TS2 are generated based on both the first hit signal and the second hit signal. Figure 20 shows the first read circuit 150, the second read circuit 130, and the logic circuit 120 in the fourth modified example.

[0151] As shown in Figure 20, the detection device 10 may have multiple first readout circuits 150. The number of first readout circuits 150 is determined according to the number of detection elements 51 of the radiation detector 50. For example, if there are 64 detection elements 51 and one first readout circuit 150 can process 32 analog signals, the detection device 10 includes two first readout circuits 150.

[0152] The first readout circuit 150 may transmit the 11th final data FD11 to the computer 110 in response to the input of the first trigger signal TS1. The 11th final data FD11 is part of the first final data FD10. The 11th final data FD11 may include the 11th hit signal H11. The 11th hit signal H11 indicates a High state when at least one of the multiple analog signals input to the first readout circuit 150 is in a High state.

[0153] As shown in Figure 20, multiple 11th hit signals H11 may be input to the OR circuit 126. The OR circuit 126 outputs the first hit signal H10.

[0154] The logic circuit 120 may include a processing circuit 127 to which the first hit signal H10 is input. The processing circuit 127 outputs a hold signal H12. The hold signal H12 remains high for the duration of the first hold period after the first hit signal H10 is generated. The first hold period is the period for waiting for electrons generated at a distance from the electron detector 30 to reach the electron detector 30. The first hold period may be less than or equal to the maximum travel time TMAX described above.

[0155] The logic circuit 120 may include a processing circuit 128 to which the 23rd hit signal H23, the 24th hit signal H24, and the hold signal H12 are input. The processing circuit 128 generates a second hit signal based on the 23rd hit signal H23 and the 24th hit signal H24. For example, the processing circuit 128 may generate a second hit signal when both the anode hit signal H23 and the cathode hit signal H24 are in a High state, similar to the AND circuit 123 described above. Alternatively, the processing circuit 128 may generate a second hit signal when either the anode hit signal H23 or the cathode hit signal H24 is in a High state, similar to the OR circuit 125 of the second modified example described above. The processing circuit 128 generates a hit signal H when the hold signal H12 is in a High state when the second hit signal is generated.

[0156] The combination of processing circuits 127 and 128 allows for the generation of a hit signal H if a second hit signal is generated within the first maintenance period after the first hit signal H10 is generated. The hit signal H is input to processing circuit 124.

[0157] When a hit signal H is input, the processing circuit 124 generates a first trigger signal TS1. The processing circuit 124 may generate the first trigger signal TS1 immediately when a hit signal H is input. Alternatively, the processing circuit 124 may generate the first trigger signal TS1 after a first delay time DT1 has elapsed since the hit signal H was input. The processing circuit 124 may generate a second trigger signal TS2 after a second delay time DT2 has elapsed since the hit signal H was input.

[0158] Figure 21 shows an example of signal processing in the fourth modification. When scattered radiation R2 is detected by the radiation detector 50, the first readout circuit 150 generates first data D10. Figure 21 shows the first hit signal H10 of the first data D10. From the time the first hit signal H10 is generated until the first hold period KT1, the hold signal H12 remains in a High state.

[0159] When a second hit signal is generated during the first hold period KT1, a first trigger signal TS1 and a second trigger signal TS2 are generated. In the example shown in Figure 21, for the fourth first data D10 from the left, the 21st data D21 and 22nd data D22 are generated during the first hold period KT1, and a second hit signal is generated. Therefore, the fourth first data D10 from the left is sent to the computer 110. In addition, the 21st data D21 and 22nd data D22, which are generated in conjunction with the fourth first data D10 from the left, are also sent to the computer 110.

[0160] On the other hand, for the 21st data D21 and 22nd data D22, the first from the left, the corresponding 1st data D10 is not generated. Therefore, the 2nd trigger signal TS2 is not generated. This situation can occur when electrons not caused by Compton scattering are detected by the electron detector 30. The 21st data D21 and 22nd data D22, the first from the left, are erased without being transmitted to the computer 110.

[0161] According to this modification, secondary data D20, such as the 21st data D21 and 22nd data D22, which relate to electrons not caused by Compton scattering, is erased without being transmitted to the computer 110. Therefore, the amount of secondary data D20 transmitted to the computer 110 can be reduced. This reduces the load on the computer 110. For example, the load required for calculation processing and image processing of secondary data D20 is reduced. For example, the load required for communication of secondary data D20 is reduced. As a result, the computer 110 can prioritize processing of highly useful data. Therefore, for example, the incident direction of radiation incident on the container 20 can be calculated more quickly than with a conventional computer 110. As a result, for example, when the detection device 10 detects radiation emitted from a radiopharmaceutical in the patient's body, the degree of radiation exposure to the patient can be reduced.

[0162] (Fifth variation) In the above-described embodiment, as shown in Figure 7, the calculation method was explained assuming that the analog signal of the radiation detector 50 is generated at time t0. In this modified example, as shown in Figure 24, an example is described in which the analog signal of the radiation detector 50 is generated after time ΔT3 from time t0. Time ΔT3 may be the difference between the time when the first hit signal H10 rises and time t0. The first hit signal H10 is obtained by digitizing the analog signal of the radiation detector 50. Time ΔT3 is also called the detection delay time.

[0163] In Figure 24, ΔT4 represents the time from when radiation is detected by the radiation detector 50 until electrons are detected by the electron detector 30. Time ΔT4 may also be the difference between the time when the first hit signal H10 rises and the time when the second hit signal H20 rises.

[0164] Time ΔT2 is calculated by adding time ΔT3 to time ΔT4. Time ΔT2 corresponds to the time required for electron e2 to travel from the endpoint of electron cloud R3 to electron detector 30. Time ΔT1 is also calculated considering time ΔT3. Time ΔT1 corresponds to the time required for electron e1 to travel from the starting point of electron cloud R3 to electron detector 30. Computer 110 may determine the position of the electron cloud considering time ΔT2 and time ΔT1. For example, computer 110 may determine the coordinates of electrons e1 and e2 in the first direction D1 considering time ΔT2 and time ΔT1. For example, computer 110 may image the electron cloud considering time ΔT2 and time ΔT1.

[0165] Time ΔT3 is dependent on the radiation detector 50. For example, time ΔT3 in a radiation detector 50 including a semiconductor detection element may be larger than time ΔT3 in a radiation detector 50 including a scintillator.

[0166] The computer 110 may obtain information about time ΔT3 from the radiation detector 50. For example, the radiation detector 50 may transmit a digitized signal containing information about time ΔT3 to the computer 110. The computer 110 may calculate information about time ΔT3 based on the analog signal from the radiation detector 50.

[0167] If the radiation detector 50 includes a semiconductor detection element, there may be some relationship between time ΔT3 and the intensity of the analog signal. The semiconductor detection element includes a cathode electrode and an anode electrode. After radiation R2 passes through the cathode electrode, electrons are generated at a position between the cathode electrode and the anode electrode. If the energy of radiation R2 is low, electrons are generated at a position far from the anode electrode. In this case, the distance the electrons travel to reach the anode electrode is long, so time ΔT3 is large. Also, because the energy of radiation R2 is low, the intensity of the analog signal is also low. On the other hand, if the energy of radiation R2 is high, electrons are generated at a position close to the anode electrode. In this case, the distance the electrons travel to reach the anode electrode is short, so time ΔT3 is small. Also, because the energy of radiation R2 is high, the intensity of the analog signal is also high. Time ΔT3 can be calculated based on the intensity of the analog signal.

[0168] (Sixth variation) In the above-described embodiment, an example was shown in which the first trigger signal TS1 is generated starting from a signal from the electron detector 30. For example, Figures 12, 14, 17, and 21 show an example in which the first trigger signal TS1 is generated when a second hit signal is generated. For example, Figure 15 shows an example in which the first trigger signal TS1 is generated after a first delay time DT1 has elapsed since the second hit signal was generated. In this modified example, an example is described in which the first trigger signal TS1 is generated starting from a signal from the radiation detector 50.

[0169] Figure 25 shows the signal processing in the sixth modified example. The first trigger signal TS1 may be generated after a first delay time DT1 has elapsed since the first hit signal H10 of the first data was generated.

[0170] The first delay time DT1 may be the same as the maximum travel time TMAX described above. The first delay time DT1 may be approximately the same as the maximum travel time TMAX described above. "Approximately the same" means that the first delay time DT1 is between 0.90 and 1.00 times the maximum travel time TMAX. The first delay time DT1 may be between 0.45 and 1.00 times the maximum travel time TMAX.

[0171] The first trigger signal TS1 may be generated only after a first delay time DT1 has elapsed since the generation of the first hit signal H10, and only if it has been confirmed that the second hit H20 was generated during the first delay time DT1. In other words, if the second hit H20 was not generated during the first delay time DT1, the first trigger signal TS1 may not be generated after the first hit signal H10 was generated and the first delay time DT1 has elapsed.

[0172] As shown in Figure 25, the second trigger signal TS2 may also be generated after the first hit signal H10 has been generated and the first delay time DT1 has elapsed. The second trigger signal TS2 may be generated only after the first delay time DT1 has elapsed and it has been confirmed that the second hit H20 was generated during the first delay time DT1. In other words, if the second hit H20 was not generated during the first delay time DT1, the second trigger signal TS2 does not need to be generated after the first hit signal H10 has been generated and the first delay time DT1 has elapsed.

[0173] Figure 26 shows an example of how to calculate time ΔT2. After the first trigger signal TS1 is generated, time ΔT5 is calculated. Time ΔT5 is the difference between the time when the second hit H20 rises and the time when the first trigger signal TS rises. Time ΔT2 is calculated by subtracting time ΔT5 from the sum of time ΔT3 and the first delay time DT1.

[0174] (supplement) As in the embodiments and modifications described above, "generating a hit signal" may mean "setting the hit signal to a High state." Similarly, "generating a trigger signal" may mean "setting the trigger signal to a High state." If the circuit of the detection device 10 performs some operation upon receiving a Low state signal, "generating a signal to generate a hit signal" may mean "setting the hit signal to a Low state." Similarly, "generating a signal to generate a trigger signal" may mean "setting the trigger signal to a Low state."

[0175] We have described several variations of the above-described embodiment, but of course, it is also possible to combine multiple variations as appropriate and apply them to the above-described embodiment. [Explanation of Symbols]

[0176] 5. Object 10 Detection device 20 containers 30 Electron detectors 31 Anode electrode 32 Cathode electrodes 35 Base material 40 Drift electrodes 45 Drift Cage 50 Radiation detectors 51 detection element 52 Circuit boards 60 Electronic Amplifiers 70 Auxiliary drift electrodes 110 Computer 120 Logic Circuits 130 Second readout circuit 131 Anode Readout Circuit 132 Cathode Readout Circuit 136 First Integrated Circuit 137 AD Converters 138 Second Integrated Circuit 1381 Buffer No. 21 1382 Buffer No. 22 1383 Second Data Processing Unit 150 1st readout circuit 156 Integrated Circuits 1561 Buffer 1 1562 First Data Processing Unit

Claims

1. A detection device for detecting radiation, A container containing gas, An electron detector located inside the aforementioned container, which detects electrons generated by Compton scattering and generates an analog signal, A drift electrode facing the electron detector, A radiation detector that detects radiation scattered by the Compton scattering and generates an analog signal, A first readout circuit that digitizes the analog signal generated by the radiation detector to generate first data and stores the first data in a first buffer, The system includes a second readout circuit that digitizes the analog signal generated by the electron detector to generate second data, The first readout circuit transmits the first final data, including the first data stored in the first buffer, to an external computer in response to a first trigger signal generated starting from the analog signal of the radiation detector. The detection device includes information regarding the time when the first data was stored in the first buffer.

2. The aforementioned radiation detector includes a plurality of detection elements, The detection device according to claim 1, wherein the first final data includes information regarding the location where the radiation reaches on the radiation detector.

3. The detection device according to claim 2, wherein the first final data includes information regarding the intensity of the analog signal generated by the radiation detector.

4. The first buffer of the first read circuit holds the first data for the duration of the first storage period. The first storage period is less than or equal to the maximum travel time. The detection device according to claim 1, wherein the maximum travel time is the time required for an electron to travel from the drift electrode to the electron detector.

5. The detection device comprises logic circuits connected to the first read circuit and the second read circuit, The detection device according to any one of claims 1 to 4, wherein the logic circuit generates the first trigger signal starting from the analog signal of the radiation detector.

6. The detection device according to any one of claims 1 to 4, wherein the first trigger signal is generated in response to the generation of the second data.

7. The first readout circuit generates a first hit signal when the intensity of the analog signal from the radiation detector exceeds a threshold. The detection device according to any one of claims 1 to 4, wherein the first trigger signal is generated after a first delay time has elapsed since the first hit signal was generated.

8. The radiation detector has a detection delay time (ΔT3), The detection apparatus according to any one of claims 1 to 4, wherein the time required (ΔT2) for electrons generated by Compton scattering to travel to the electron detector is calculated based on the detection delay time (ΔT3).

9. The detection device according to claim 8, wherein the time required for electrons generated by Compton scattering to travel to the electron detector (ΔT2) is calculated by adding the detection delay time (ΔT3) to the time (ΔT4) from when radiation is detected by the radiation detector until electrons are detected by the electron detector.

10. The first readout circuit generates a first hit signal when the intensity of the analog signal from the radiation detector exceeds a threshold. The second readout circuit generates a second hit signal when the intensity of the analog signal from the electron detector exceeds a threshold. The detection device according to claim 9, wherein the time (ΔT4) from the detection of radiation by the radiation detector to the detection of electrons by the electron detector is the difference between the time the first hit signal rises and the time the second hit signal rises.

11. The first readout circuit generates a first hit signal when the intensity of the analog signal from the radiation detector exceeds a threshold. The first trigger signal is generated after a first delay time has elapsed since the first hit signal was generated. The second readout circuit generates a second hit signal when the intensity of the analog signal from the electron detector exceeds a threshold. By subtracting time (ΔT5) from the sum of the detection delay time (ΔT3) and the first delay time, the time (ΔT2) required for electrons generated by Compton scattering to travel to the electron detector is calculated. The detection device according to claim 8, wherein the aforementioned time (ΔT5) is the difference between the time when the second hit signal rises and the time when the first trigger signal rises.

12. The aforementioned first delay time is 0.45 times or more and 1.00 times or less the maximum travel time. The detection device according to claim 7, wherein the maximum travel time is the time required for an electron to travel from the drift electrode to the electron detector.

13. The detection device according to any one of claims 1 to 4, wherein the first readout circuit transmits information regarding the detection delay time in the radiation detector to the computer.

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