A high-resolution compton gamma camera

Abstract

The application discloses a high-resolution Compton gamma camera and relates to the technical field of gamma measurement, which comprises a high-pressure tank body provided with a window, a metal film is sealingly arranged at the window, and a plurality of flange interfaces are arranged on the sidewall or the bottom of the high-pressure tank body; a time projection chamber detector is arranged in the high-pressure tank body and is used for realizing three-dimensional track and energy measurement of Compton scattering conversion of gamma rays and scattered electrons; and a gamma energy measurer is located between a field cage of the time projection chamber detector and the inner wall of the high-pressure tank body and is used for realizing position and energy measurement of Compton scattering gamma and electron leakage. The application realizes high-precision measurement of Compton scattering electrons and gamma, realizes accurate measurement of the direction and energy of gamma, and provides key technical support for astronomical observation, radiotherapy, source item detection and other applications.

Description

Technical Field

[0001] This invention relates to the field of gamma measurement technology, and in particular to a high-resolution Compton gamma camera. Background Technology

[0002] The 0.3–10 MeV gamma (γ) energy range covers the characteristic spectral lines of the major known elements, making precise measurements of this range of significant scientific and industrial applications. Among existing astronomical observation instruments, the observation sensitivity of γ in the MeV energy range is 2–3 orders of magnitude lower than other energy ranges, representing a crucial observational window requiring breakthroughs. In novel radiotherapy, such as proton radiotherapy, high-precision measurement of the γ direction is key to accurately locating the range of the proton beam. Furthermore, in nuclear power safety applications, high-precision localization imaging of γ radiation sources is also of great demand.

[0003] However, the development of gamma-ray detection technology in this energy range has been slow for a long time, mainly because the wavelength of gamma rays in this range is too short to be focused using methods similar to mirrors or lenses. Most incident photons only deposit a portion of their energy through Compton scattering, making it challenging to accurately measure their incident direction and total energy. Traditional Compton cameras only measure the angle of Compton scattering gamma rays, obtaining one of two angles characterizing the direction of the incident gamma rays. Due to the lack of angular information about recoil electrons, high-sensitivity gamma-ray source observation cannot be achieved under conditions of heavy background gamma-ray contamination. Traditional Compton camera measurement methods mostly still use solid-state detectors, primarily semiconductors or scintillators, to measure the top and bottom of the Compton scattering, failing to measure the initial trajectory information of the scattered electrons. The key angular resolution of this measurement is only about 10°, which is far from meeting the needs of scientific research and applications. For example, in proton therapy, achieving millimeter-level positioning accuracy of the Bragg peak position of protons requires detectors very close to the human body and a huge number of case statistics, which cannot meet the needs of rapid imaging measurements in clinical medicine. Summary of the Invention

[0004] The purpose of this invention is to provide a high-resolution Compton gamma camera to solve the problems existing in the prior art, realize high-precision measurement of Compton scattered electrons and gamma, and at the same time realize accurate measurement of gamma direction and energy, providing key technical support for applications such as astronomical observation, radiotherapy, and source term detection.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a high-resolution Compton gamma camera, comprising a high-pressure tank with a window sealed with a metal membrane, and multiple flange interfaces on the side wall or bottom of the high-pressure tank; a time projection chamber detector disposed within the high-pressure tank for measuring the Compton scattering conversion of gamma rays and the three-dimensional trajectory and energy of scattered electrons; and a gamma calorimeter located between the field cage of the time projection chamber detector and the inner wall of the high-pressure tank for measuring the location and energy of Compton scattering gamma and electron leakage.

[0007] Optionally, the high-pressure tank has a window at one end, and the thickness of the metal membrane sealed at the window does not exceed 10mm.

[0008] Optionally, the high-pressure tank has windows at both symmetrical ends, and the thickness of the metal membrane sealed at the window does not exceed 10mm.

[0009] Optionally, the high-pressure tank can be filled with gas at a pressure of 1-15 bar; the high-pressure tank can be in a closed-loop mode or a gas recirculation mode.

[0010] Optionally, the time projection chamber detector includes a microstructure gas detector, which is located inside the high-pressure tank near the window. The end of the microstructure gas detector near the window is connected to the time projection chamber readout electronics, and the end of the microstructure gas detector away from the window is provided with the field cage.

[0011] Optionally, the microstructured gas detector is suitable for high-pressure environments and may employ a gas electron multiplier (GEM / THGEM), a micromegagas detector, a dual-layer micromegagas detector (DMM), or a resistive microwell detector (μRWELL).

[0012] Optionally, the gamma calorimeter includes a pixel semiconductor detector disposed between the field cage and the inner wall of the high-pressure tank; the pixel semiconductor detector is made of zinc cadmium telluride, cadmium telluride or perovskite material, the pixel unit size of the pixel semiconductor detector is 0.1mm to 10mm, the single layer thickness of the pixel semiconductor detector is 5mm to 30mm, and multiple layers can be arranged to improve detection efficiency.

[0013] Optionally, the gamma calorimeter includes a scintillation crystal array and a photoelectric readout detector disposed between the inner wall of the field cage and the high-pressure tank. The scintillation crystal array is composed of multiple crystal unit arrays spliced ​​together. The crystal unit is a cerium-activated lanthanum bromide crystal, lanthanum bromide crystal, sodium iodide crystal, or cesium iodide crystal. The scintillation crystal array is coupled with a photomultiplier detector or a multi-anode photomultiplier tube for photoelectric signal readout.

[0014] Optionally, the gas component is a single-component gas such as carbon tetrafluoride or methane.

[0015] Optionally, the gas composition is a mixture of an inert gas and a polyatomic gas, wherein the inert gas is argon, neon, or xenon, and the polyatomic gas is carbon dioxide, isobutane, carbon tetrafluoride, methane, or ethane.

[0016] The present invention achieves the following technical effects compared to the prior art:

[0017] This invention employs time projection chamber technology based on advanced gas detectors, combined with pixel-type semiconductor detectors or high-resolution scintillator calorimeters, to achieve high-precision measurement of Compton-scattered electrons and gamma rays, as well as accurate measurement of gamma direction and energy. Specifically, compared to traditional solid-state Compton scatterer (such as scintillators or semiconductors) solutions, this invention achieves high-precision measurement of the angle and energy of Compton-scattered electrons, determines the Compton scattering plane, and uniquely locates the gamma incident direction. Compared to other time projection chamber solutions, this invention uses a microstructured gas detector with high energy and high position resolution, combined with a novel pixel-type semiconductor detector or high-resolution scintillator calorimeter, to achieve high-precision measurement of gamma energy and incident direction. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the high-resolution Compton gamma camera structure of the present invention;

[0020] Figure 2 This is a schematic diagram of the high-pressure tank structure of the present invention;

[0021] Figure 3 This is another structural schematic diagram of the high-pressure tank body in different embodiments of the present invention;

[0022] Figure 4This is a schematic diagram of the time projection chamber detector of the present invention;

[0023] Figure 5 This is a schematic diagram of the pixel semiconductor detector of the present invention;

[0024] Figure 6 This is a schematic diagram of the scintillation crystal array + photoelectric readout detector of the present invention;

[0025] Figure 7 This is a schematic diagram of the scintillation crystal array + photoelectric readout detector in another embodiment of the present invention;

[0026] Explanation of reference numerals in the attached drawings: 1-High-pressure tank, 2-Window, 3-Metal membrane, 4-Flange interface, 5-Time projection chamber detector, 501-Microstructure gas detector, 502-Time projection chamber readout electronics, 503-Field cage, 6-Gamma calorimeter. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The purpose of this invention is to provide a high-resolution Compton gamma camera to solve the problems existing in the prior art, realize high-precision measurement of Compton scattered electrons and gamma, and at the same time realize accurate measurement of gamma direction and energy, providing key technical support for applications such as astronomical observation, radiotherapy, and source term detection.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] This invention provides a high-resolution Compton gamma camera, see attached figure. Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 Appendix Figure 5 Appendix Figure 6 and attached Figure 7As shown, the device includes a high-pressure tank 1, with a window 2 at one end. A metal membrane 3, no more than 10 mm thick, is sealed at the window 2. The membrane material can be stainless steel, titanium alloy, aluminum alloy, carbon fiber, etc. Multiple flange interfaces 4, serving as leads for detector gas, high-voltage power, and electronic signals, are located on the side wall or bottom of the high-pressure tank 1. The high-pressure tank 1 can be supplied with gas at a pressure of 1-15 bar, allowing it to operate in either a closed-loop or gas circulation mode. The gas composition is either a single-component gas such as carbon tetrafluoride or methane, or a mixture of inert and polyatomic gases. The inert gas is argon, neon, or xenon, and the polyatomic gases are carbon dioxide, isobutane, carbon tetrafluoride, methane, or ethane. A time projection chamber detector 5, including a microstructure gas detector 501, is fixed inside the high-pressure tank 1 near the window 2. Near window 2, a time projection chamber readout electronics 502 is connected to the signal. A field cage 503 is located at the end of the microstructure gas detector 501 furthest from window 2. The field cage 503 is composed of fine metal wires or metal strips, typically employing a double-layer structure to improve electric field uniformity. A microstructure gas detector 501 is used as the signal readout detector. This selected microstructure gas detector 501 is suitable for high-pressure environments, such as gas electron multipliers, microgrid gas detectors, double-layer microgrid gas detectors, and resistive microwell detectors. Combined with corresponding low-noise multi-channel readout electronics, it enables the measurement of gamma-ray Compton scattering conversion and the three-dimensional trajectory and energy of scattered electrons. The microstructure gas detector 501 uses two-dimensional crossbar readout or pixel readout, with the readout bar or pixel spacing typically ranging from 0.1mm to 10mm. A gamma calorimeter 6 is located between the field cage 503 of the time projection chamber detector 5 and the inner wall of the high-pressure tank 1, used to measure the location and energy of Compton scattering gamma and electron leakage.

[0031] In a further preferred embodiment, the gamma calorimeter 6 includes a pixel semiconductor detector disposed between the field cage 503 and the inner wall of the high-pressure tank 1; the pixel semiconductor detector is made of zinc cadmium telluride, cadmium telluride or perovskite material, the pixel unit size of the pixel semiconductor detector is 0.1mm to 10mm, and the single layer thickness of the pixel semiconductor detector is 5mm to 30mm. In use, multiple units are usually spliced ​​together to achieve a larger sensitive area, and then multiple layers are set to ensure sufficient detection efficiency. In addition to the structure described above, the gamma calorimeter 6 can also employ a scintillation crystal array combined with a photoelectric readout detector. The scintillation crystal array is composed of multiple crystal unit arrays spliced ​​together. The crystal units are cerium-activated lanthanum bromide crystals, sodium iodide crystals, or cesium iodide crystals. The scintillation crystal array is coupled with a photomultiplier detector or a multi-anode photomultiplier tube for photoelectric signal readout. Pixel readout typically uses an encoded multiplexing method to reduce the readout scale. The crystal unit width is typically 3mm–20mm, and the single-layer thickness is 5–30mm. Multiple layers are usually used to ensure sufficient detection efficiency. Furthermore, in another embodiment, considering that some high-energy gamma rays cannot be completely absorbed by the gamma calorimeter 6, a larger scintillator detector is added to the bottom or outer side of the gamma calorimeter 6 as a gamma residual energy absorption detector, while also serving as an anti-coincidence detector.

[0032] In one different embodiment, windows 2 are provided at both symmetrical ends of the high-pressure tank 1. The thickness of the metal film 3 sealed at the window 2 does not exceed 10mm. By combining different high-pressure tank 1 structures, time projection chamber detectors 5 and gamma calorimeters 6, the complete system of the present invention can be formed.

[0033] In the description of this invention, it should be noted that the terms "center," "top," "bottom," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A high-resolution Compton gamma camera, characterized in that: It includes a high-pressure tank body, which is provided with a window, and a metal membrane is sealed at the window. The high-pressure tank body has multiple flange interfaces on its side wall or bottom. A time projection chamber detector, which is installed inside the high-pressure tank, is used to realize the Compton scattering conversion of gamma rays and the three-dimensional track and energy measurement of scattered electrons; A gamma calorimeter, located between the field cage of the time projection chamber detector and the inner wall of the high-pressure tank, is used to measure the location and energy of Compton scattering gamma and electron leakage. The time projection chamber detector includes a microstructured gas detector, which is located inside the high-pressure tank near the window. The end of the microstructured gas detector near the window is connected to the time projection chamber readout electronics, and the end of the microstructured gas detector away from the window is equipped with the field cage. The gamma calorimeter includes a pixel semiconductor detector located between the field cage and the inner wall of the high-pressure tank. The pixel semiconductor detector is made of cadmium zinc telluride, cadmium telluride, or perovskite material. The pixel unit size of the pixel semiconductor detector is 0.1mm~10mm, and the single-layer thickness of the pixel semiconductor detector is 5mm~30mm, with multiple layers arranged to improve detection efficiency. The high-pressure tank has a window at one end, and the thickness of the metal membrane sealed at the window does not exceed 10 mm; the high-pressure tank can be filled with gas at a pressure of 1-15 bar; the high-pressure tank can be used in a gas sealing mode or a gas circulation mode; the microstructure gas detector is suitable for high-pressure environments, and the microstructure gas detector is a gas electron multiplier, a microgrid gas detector, a double-layer microgrid gas detector, or a resistive microwell detector.

2. The high-resolution Compton gamma camera according to claim 1, characterized in that: The high-pressure tank has windows at both symmetrical ends, and the thickness of the metal membrane sealed at the windows does not exceed 10mm.

3. The high-resolution Compton gamma camera according to claim 1, characterized in that: The gamma calorimeter includes a scintillation crystal array and a photoelectric readout detector disposed between the field cage and the inner wall of the high-pressure tank. The scintillation crystal array is composed of multiple crystal unit arrays spliced ​​together. The crystal unit is a cerium-activated lanthanum bromide crystal, lanthanum bromide crystal, sodium iodide crystal, or cesium iodide crystal. The scintillation crystal array is coupled with a photomultiplier detector or a multi-anode photomultiplier tube for photoelectric signal readout.

4. The high-resolution Compton gamma camera according to claim 1, characterized in that: The gas is a single-component gas, which is carbon tetrafluoride or methane.

5. The high-resolution Compton gamma camera according to claim 1, characterized in that: The gas composition is a mixture of an inert gas and a polyatomic gas, wherein the inert gas is argon, neon, or xenon, and the polyatomic gas is carbon dioxide, isobutane, carbon tetrafluoride, methane, or ethane.

Images