A compact gamma ray detection optical system and detection method

Abstract

The present invention provides a compact gamma-ray detection optical system and detection method, which solves the problems of low time resolution of fusion process detection and interference with adjacent equipment in the prior art. The system includes a sealed shell, a detector, and a converter, a secondary reflector, and a primary reflector arranged along the gamma-ray emission direction; a sealing sleeve is arranged in the sealed shell, one end of the sealing sleeve is sealed by a pressure sealing window, and the other end is connected to the sealed shell; a cavity formed by the sealing sleeve, the pressure sealing window, and the sealed shell is filled with high-pressure gas; the primary reflector is sleeved on the sealing sleeve; the detector is arranged in the sealing sleeve, and the detection surface is located between the primary reflector and the secondary reflector; both the primary and secondary reflectors are concave reflectors, and the distance between the two satisfies: T1<T<T2; T is the time when the gamma ray enters the converter to generate photons and reaches the detection surface through the primary, secondary reflectors, and the pressure sealing window; T1 is the time when the direct gamma ray reaches the detection surface; T2 is the time when the secondary gamma ray reaches the detection surface.

Description

Technical Field

[0001] The invention relates to a fusion process detection technology, and in particular to a compact gamma ray detection optical system and a detection method used in nuclear fusion research. Background Art

[0002] Fusion energy is a non-polluting clean energy, and countries around the world are competing to invest a lot of manpower and material resources in the research and development of related technologies. However, the conditions for achieving fusion are extremely harsh, and the fuel needs to reach extremely high temperature and high pressure. Currently, laser inertial confinement fusion (ICF) and magnetic confinement fusion are the two most promising technical approaches to achieve this condition.

[0003] In laser inertial confinement fusion, high-energy laser is incident on a black cavity, and energy is deposited on its inner wall, generating X-ray radiation; the X-ray is reabsorbed and re-radiated by the black cavity, eventually forming a uniform radiation field inside the black cavity; it then irradiates and ablates the target capsule, causing it to implode centripetally, and the fusion fuel is compressed to extremely high temperature and pressure, causing thermonuclear fusion to occur, releasing a large amount of energy in the form of neutron radiation, gamma-ray radiation, etc.

[0004] Neutrons and gamma rays are characteristic products of fusion reactions, and their radiation process characterizes the fusion process of fusion fuel. At present, in the research of laser inertial confinement fusion, fusion process diagnostic technology based on neutron emission detection has been developed and successfully applied to laser fusion devices, and fusion process data has been obtained, providing key technical support for ICF theoretical research.

[0005] However, since neutrons have mass, neutrons of different energies (different speeds, different energies) have different flight speeds. Even if the neutrons are radiated at the same time, after flying a certain distance, there will be a lot of time dispersion and they will arrive at the neutron detector one after another. In this way, the neutrons radiated at different times are superimposed on each other on the detector, which greatly reduces the time resolution ability of fusion process detection. In practical applications, in order to reduce this time dispersion, the detector is often brought close to the fusion fuel (2cm-20cm) to reduce the flight distance. However, close detection occupies a large solid angle, which seriously interferes with the observation and diagnosis channels of adjacent equipment. Summary of the invention

[0006] In order to solve the technical problems in the prior art that the time resolution capability of fusion process detection is greatly reduced, and in order to reduce time dispersion, the detector is brought close to the fusion fuel, resulting in interference with the operation of adjacent equipment, the present invention provides a compact gamma-ray detection optical system and detection method.

[0007] To achieve the above purpose, the technical solution provided by the present invention is:

[0008] A compact gamma-ray detection optical system, which is special in that it includes a sealed housing, a converter, a primary reflector, a secondary reflector and a detector;

[0009] A sealing sleeve is provided in the sealing housing, and one end of the sealing sleeve is sealed by a pressure sealing window, and the other end is connected to the rear end cover of the sealing housing; a through hole matching the sealing sleeve is provided in the middle of the rear end cover, and the sealing sleeve is sealingly connected to the rear end cover outside the through hole; a cavity formed by the sealing sleeve, the pressure sealing window and the sealing housing is filled with high-pressure gas;

[0010] The converter, the secondary reflector and the primary reflector are coaxially arranged in the sealed housing in sequence along the gamma ray emission direction, and the primary reflector is sleeved on the sealing sleeve; the primary reflector and the secondary reflector are both concave reflectors;

[0011] The detector is arranged in the sealing sleeve, and the detection surface of the detector is located between the primary reflector and the secondary reflector;

[0012] Gamma rays pass through the front cover of the sealed shell and enter the converter. They collide with the electrons of the converter to excite high-speed electrons. The high-speed electrons and high-pressure gas generate Cherenkov photons. The photons are reflected by the primary reflector and the secondary reflector in turn, pass through the pressure sealing window, and reach the detection surface of the detector.

[0013] The distance between the primary reflector and the secondary reflector must satisfy: T1<T<T2;

[0014] Wherein, T is the time when the gamma ray is incident on the converter, the generated Cherenkov photons pass through the primary reflector, the secondary reflector, the pressure sealing window, and reach the detection surface of the detector;

[0015] T1 is the time required for gamma rays to pass through the converter, secondary reflector, pressure sealing window in sequence and reach the detection surface of the detector;

[0016] T2 is the time required for the secondary gamma rays generated by gamma radiation to reach the detection surface of the detector.

[0017] Furthermore, N light-blocking rings are provided in the sealed housing along the emission direction of the gamma rays for filtering out stray light, where N is a positive integer and N≥2.

[0018] Furthermore, a shielding ring is provided in the sealed housing to filter out large-angle Cherenkov photons;

[0019] The N light-blocking rings are a first light-blocking ring, a second light-blocking ring, ... an Nth light-blocking ring, which are sequentially arranged along the gamma-ray emission direction;

[0020] The shielding ring is located between the first light blocking ring and the second light blocking ring, and is arranged adjacent to the first light blocking ring.

[0021] Furthermore, a secondary mirror front shielding body is provided on the end surface of the secondary reflector close to the converter;

[0022] The end surface of the secondary reflector close to the detector is provided with a secondary mirror gap shielding body;

[0023] The end surface of the primary reflector close to the secondary reflector is provided with a probe outer shielding body, which is sleeved on the sealing sleeve.

[0024] Furthermore, the distance from the primary reflector to the converter is 1058 mm, the distance from the secondary reflector to the converter is 950 mm, the distance from the pressure sealing window to the converter is 1009 mm, and the distance from the detection surface of the detector to the converter is 1027 mm.

[0025] Further, the spherical radius of the primary reflector is -383.88;

[0026] The quadratic coefficient k and the second-order coefficient α of the primary reflector 1 , the fourth-order coefficient α 2 , the sixth-order coefficient α 3 , eighth-order coefficient α 4 , tenth-order coefficient α 5 They are -0.355412 and -2.578422×10 -4 3.238440×10 -9 , 6.868379×10 -15 ,1.380407×10 -17 , -7.828763×10 -22 ;

[0027] The spherical radius of the secondary reflector is 59.55;

[0028] The quadratic coefficient k and the second-order coefficient α of the secondary reflector 1 , the fourth-order coefficient α 2 , the sixth-order coefficient α 3 , eighth-order coefficient α 4 , tenth-order coefficient α 5 They are -3.023504 and -8.155204×10 -3 ,1.295230×10 -6 , -3.302616×10 -10 8.337472×10 -14 , -1.197747×10 -17 ;

[0029] The surface shapes of the primary reflector and the secondary reflector are both even-order aspheric surfaces, and the surface shape formula is as follows:

[0030]

[0031] Where: z is the sag of the reflector; c is the inverse of the spherical radius; r is the radial variable.

[0032] Furthermore, the diameters of the converter, primary reflector, secondary reflector, pressure sealing window and detector detection surface are 70 mm, 170 mm, 80 mm, 40 mm and 10 mm respectively.

[0033] Furthermore, the material of the converter is beryllium, and the materials of the primary reflector and the secondary reflector are both aluminum.

[0034] The pressure sealing window is a sapphire pressure sealing window;

[0035] The high pressure gas is CO 2 or C 2 F 6 .

[0036] At the same time, the present invention provides a compact gamma ray detection method, which is special in that it includes the following steps:

[0037] 1) Gamma rays pass through the sealed shell and enter the converter, colliding with the electrons in the converter to excite high-speed electrons;

[0038] 2) The speed of high-speed electrons exceeds the speed of light in the high-pressure gas in the sealed shell, and the high-speed electrons and the high-pressure gas produce Cherenkov photons;

[0039] 3) The primary reflector and the secondary reflector fold the optical path of the Cherenkov photons so that they pass through the pressure sealing window and reach the detection surface of the detector;

[0040] The distance between the primary reflector and the secondary reflector must satisfy: T1<T<T2;

[0041] Wherein, T is the time when the gamma ray is incident on the converter, the generated Cherenkov photons pass through the primary reflector, the secondary reflector, the pressure sealing window, and reach the detection surface of the detector;

[0042] T1 is the time required for gamma rays to pass through the converter, secondary reflector, pressure sealing window in sequence and reach the detection surface of the detector;

[0043] T2 is the time required for the secondary gamma rays generated by gamma radiation to reach the detection surface of the detector;

[0044] 4) The detector detects the photon history of reaching the detector detection surface in step 3) at time T, and obtains the gamma ray radiation history.

[0045] Compared with the prior art, the advantages of the present invention are:

[0046] 1. The detection optical system of the present invention detects gamma rays. Since gamma rays have extremely strong penetrability and do not have the problem of neutron flight time dispersion, they can be detected in real time at a long distance and have higher time resolution. Gamma rays are incident on the converter to generate high-speed electrons, which generate Cherenkov radiation photons in the high-pressure gas of the sealed shell. The gamma ray radiation history can be indirectly obtained by detecting the photon emission process; the primary reflector and the secondary reflector are used to fold the optical path so that the Cherenkov radiation photons arrive after the direct gamma rays reach the detector and before the secondary gamma rays reach the detector, effectively removing interference information. The photon emission process of the time T arriving at the detection surface is detected by a detector with ultrafast time response, and the gamma ray radiation history can be indirectly obtained.

[0047] 2. The primary reflector and the secondary reflector in the detection optical system of the present invention adopt aspheric reflectors. Different from the conventional typical Cassegrain optical path, the primary reflector and the secondary reflector are both concave reflectors (the primary reflector of the Cassegrain system is concave, and the secondary reflector is convex). The system of the present invention has a shorter image distance, so that the detection surface of the detector is placed between the primary reflector and the secondary reflector, avoiding the secondary radiation generated by the gamma ray incident on the primary reflector in the same direction as the gamma radiation direction affecting the measurement results.

[0048] 3. The present invention provides a light-blocking ring and a shielding ring in the sealed housing to effectively filter out stray light and stray Cherenkov photon interference.

[0049] 4. The primary reflector and the secondary reflector of the present invention are made of an aluminum substrate and are processed by diamond CNC turning, so that the cost is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the structure of the compact gamma-ray detection optical system of the present invention. Figure 1 (collecting Cherenkov photons at the front position);

[0051] Figure 2 This is a schematic diagram of the structure of the compact gamma-ray detection optical system of the present invention. Figure 2 (collecting Cherenkov photons in the middle position);

[0052] Figure 3 This is a schematic diagram of the structure of the compact gamma-ray detection optical system of the present invention. Figure 3 (collecting Cherenkov photons at the middle and rear positions);

[0053] The reference numerals are as follows:

[0054] 1-conversion body, 2-primary reflector, 3-secondary reflector, 4-pressure sealing window, 5-detector, 6-shielding ring, 7-secondary mirror front shielding body, 8-secondary mirror gap shielding body, 9-probe outer shielding body, 10-light blocking ring, 11-sealing shell, 12-front cover, 13-inflation valve, 14-pressure gauge, 15-rear cover, 16-sealing sleeve. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0056] Since gamma rays have extremely strong penetrability and no flight time dispersion problem, they can be detected in real time at a long distance and have higher time resolution. Therefore, the present invention proposes a fusion process diagnostic optical system based on gamma ray detection. In this system, gamma rays are incident on beryllium and other converters 1, and gamma rays bombard beryllium atoms to generate high-speed electrons. The high-speed electrons are in the high-pressure gas (CO 2 , C 2 F 6 Cherenkov radiation photons are produced in the atmosphere (such as radio waves, radio telescopes, etc.). By detecting the photon emission process, the gamma-ray radiation process can be indirectly obtained.

[0057] like Figure 1 As shown, a compact gamma-ray detection optical system is used to obtain fusion process information based on the detection of the radiation process of fusion characteristic products (gamma rays). The detection optical system includes a sealed shell 11, a sealed sleeve 16 and an optical element. The optical element includes a converter 1, a primary reflector 2, a secondary reflector 3 and a detector 5. A through hole matching the sealing sleeve 16 is provided in the middle of the rear end cover 15 of the sealed shell 11. The sealing sleeve 16 is located in the sealed shell 11, and one end of the sealing sleeve 16 is sealed by a pressure sealing window 4, and the other end is connected to the through hole of the sealed shell 11. ; A sealed cavity is formed by a sealing sleeve 16, a pressure sealing window 4 and a sealed shell 11, and the cavity is filled with high-pressure gas; a converter 1, a secondary reflector 3 and a primary reflector 2 are coaxially arranged in sequence along the gamma ray emission direction and are located in the sealed shell 11, and the primary reflector 2 is sleeved on the sealing sleeve 16, and both the primary reflector 2 and the secondary reflector 3 are concave reflectors; the converter 1 is close to the front end cover 12 of the sealed shell 11, and the detector 5 is arranged in the sealing sleeve 16 at the rear end through hole of the sealed shell 11, and the detection surface of the detector 5 is located between the primary reflector 2 and the secondary reflector 3.

[0058] Gamma rays pass through the front end cover 12 of the sealed shell 11 and are incident on the converter 1, colliding with the electrons of the converter 1 to excite high-speed electrons. The high-speed electrons and the high-pressure gas generate Cherenkov photons, which are collected by the primary reflector 2 and reflected by the secondary reflector 3 in turn, and then pass through the pressure sealing window 4 to reach the detection surface of the detector 5.

[0059] The parameters of the optical elements in the optical system of this embodiment are shown in Table 1 below

[0060] Table 1 Optical element parameters

[0061]

[0062] In Table 1, the coordinate data is as follows: Figure 1 In the right-hand coordinate system shown, the horizontal right is the +Z axis, the vertical inward is the +X axis, and the upward is the +Y axis. The radius of the primary reflector 2 and the secondary reflector 3 is defined as follows: if the center of the sphere is on the left side of the mirror body, the radius is negative; if the center of the sphere is on the right side of the mirror body, the spherical radius is positive. The surface shapes of the primary reflector 2 and the secondary reflector 3 are both even-order aspherical surfaces, and their surface shape formulas are shown in the following formula (1):

[0063] Even-order aspheric surface formula:

[0064]

[0065] Where: z is the sag of the reflector; c is the inverse of the spherical radius; k is the coefficient of the quadratic curve; α 1 ~α 5 : Even aspheric coefficient; r is the radial variable.

[0066] The optical system of this embodiment can collect light emitting signals at different Z-direction positions in the sealed housing 11, such as Figures 1 to 3 Therefore, the Cherenkov photons at different Z-direction positions in the sealed housing 11 of the detection optical system of this embodiment can all reach the detector 5, thereby improving the signal collection and detection capability.

[0067] A key problem in the optical system of this embodiment is to remove interference signals. The sources of interference signals mainly include three aspects: direct gamma interference, secondary gamma interference, and stray Cerenkov photon interference.

[0068] Direct gamma interference: refers to the gamma radiation generated in the laser fusion process, which passes through the front cover 12 of the high-pressure sealed shell 11, the converter 1, the secondary reflector 3, the pressure sealing window 4 in sequence, and reaches the detection surface of the detector 5, generating signal interference;

[0069] Secondary gamma interference: refers to the gamma radiation generated during the laser fusion process, which encounters various detection instruments arranged around its circumference, collides with the material atomic nuclei to generate secondary gamma rays, and collides with the sealed shell 11 to generate secondary gamma rays, which eventually reach the detection surface of the detector 5, forming signal interference;

[0070] Stray Cherenkov photon interference refers to Cherenkov photons generated inside the sealed housing 11 and not collected by the optical system. After multiple scattering by various components inside the sealed housing 11, they reach the detection surface of the detector 5, forming signal interference.

[0071] In view of the above three major interference signals, the optical system of this embodiment is designed to filter out interference.

[0072] First, (filtering out direct gamma interference and secondary gamma interference) use the arrival time difference between direct gamma and secondary gamma to identify and filter out interference. Direct gamma does not undergo any deflection. The gamma radiation passes through the converter 1, the secondary reflector 3, and the pressure sealing window 4 in sequence to reach the detection surface of the detector 5. It is the first signal to arrive at the detector 5. Since the secondary gamma rays undergo a deflection of more than 500 mm (the conventional requirement for the distance between the diagnostic equipment and the fusion target), the secondary gamma arrives at the detector 5 about 16.7 ns later than the direct gamma. The time period of 16.7 ns from the arrival of the direct gamma to the arrival of the secondary gamma is the time window without gamma interference. Therefore, the distance between the primary reflector 2 and the secondary reflector 3 designed in this embodiment must satisfy the following requirements: T1<T<T2;

[0073] Wherein, T is the time when the gamma ray is incident on the converter 1, generates Cherenkov photons, passes through the primary reflector 2, the secondary reflector 3, the pressure sealing window 4, and reaches the detection surface of the detector 5;

[0074] T1 is the time required for the gamma ray to pass through the converter 1, the secondary reflector 3, the pressure sealing window 4 in sequence and reach the detection surface of the detector 5;

[0075] T2 is the time required for the secondary gamma rays generated by the gamma radiation to reach the detection surface of the detector 5.

[0076] According to the 16.7 ns time window, the optical system of this embodiment uses the primary reflector 2 and the secondary reflector 3 to fold the optical path by 220 mm (the optical path after folding by the primary and secondary reflectors 3 differs from the straight optical path from the fusion target to the detector 5 by 220 mm), so that the Cherenkov signal arrives 7.3 ns after the direct gamma ray arrives, and the signal is identified by the detector 5 with ultrafast time response so as to be filtered out.

[0077] Secondly, (filtering out stray Cherenkov photon interference) optical multi-stage light-blocking rings and shielding units are used; the multi-stage light-blocking rings are specifically: a plurality of spaced light-blocking rings 10 are provided in the sealed shell 11 for filtering out stray light. In the present embodiment, the number of the light-blocking rings 10 is 5, and the 5 light-blocking rings 10 are coaxially arranged in sequence along the gamma-ray emission direction, namely the first light-blocking ring, the second light-blocking ring...the fifth light-blocking ring; a shielding ring 6 is also provided in the sealed shell 11 for filtering out large-angle Cherenkov photons, and the shielding ring 6 is located between the first light-blocking ring and the second light-blocking ring, and is arranged adjacent to the first light-blocking ring. The shielding unit comprises a secondary mirror front shielding body 7 arranged on the front end face of the secondary reflector 3, a secondary mirror gap shielding body 8 arranged on the rear end face of the secondary reflector 3, and a probe outer shielding body 9 arranged on the front end face of the primary reflector 2. The secondary mirror front shielding body 7 has a structural shape of a solid frustum, and the front end diameter is smaller than the rear end diameter; the secondary mirror gap shielding body 8 has a structural shape of a solid cone, and the bottom surface of the cone is arranged on the rear end face of the secondary reflector; the probe outer shielding body 9 has a structural shape of a tubular body with a cone angle on the outer wall, and the front end outer diameter is smaller than the rear end outer diameter.

[0078] The optical system of this embodiment further includes a pressure gauge 14 and a gas charging valve 13 disposed on the sealed housing 11 , which are used to measure the pressure in the sealed housing 11 and to replenish the sealed housing 11 with high-pressure gas, respectively.

[0079] Based on the above detection optical system, this embodiment provides a compact gamma ray detection method, comprising the following steps:

[0080] 1) Gamma rays pass through the sealed housing 11 and enter the converter 1, colliding with the electrons in the converter 1 to excite high-speed electrons;

[0081] 2) The speed of high-speed electrons exceeds the speed of light in the high-pressure gas in the sealed housing 11, and the high-speed electrons and the high-pressure gas generate Cherenkov photons;

[0082] 3) The Cherenkov photons are deflected by the primary reflector 2 and the secondary reflector 3, so that the time T when they pass through the pressure sealing window 4 and reach the detection surface of the detector 5 is later than the time T1 when the direct gamma radiation reaches the detection surface of the detector 5, and earlier than the time T2 when the secondary gamma radiation reaches the detection surface of the detector 5;

[0083] 4) The detector 5 detects the photon history reaching the detection surface of the detector 5 at time T, and can indirectly obtain the gamma ray radiation history.

[0084] The above is only a description of the preferred implementation mode of the present invention, and the technical solution of the present invention is not limited thereto. Any known deformation made by those skilled in the art on the basis of the main technical concept of the present invention belongs to the technical scope to be protected by the present invention.

Claims

1. A compact gamma-ray detection optical system, characterized in that: It comprises a sealed housing (11), a converter (1), a primary reflector (2), a secondary reflector (3) and a detector (5); A sealing sleeve (16) is provided in the sealing housing (11), one end of the sealing sleeve (16) is sealed by a pressure sealing window (4), and the other end is connected to a rear end cover (15) of the sealing housing (11); a through hole matching the sealing sleeve (16) is provided in the middle of the rear end cover (15), and the sealing sleeve (16) is sealingly connected to the rear end cover (15) outside the through hole; a cavity formed by the sealing sleeve (16), the pressure sealing window (4) and the sealing housing (11) is filled with high-pressure gas; The converter (1), the secondary reflector (3), and the primary reflector (2) are coaxially arranged in sequence in a sealed housing (11) along the gamma ray emission direction, and the primary reflector (2) is sleeved on a sealing sleeve (16); the primary reflector (2) and the secondary reflector (3) are both concave reflectors; The detector (5) is arranged in the sealing sleeve (16), and the detection surface of the detector (5) is located between the primary reflector (2) and the secondary reflector (3); The gamma rays pass through the front end cover (12) of the sealed housing (11), are incident on the converter (1), collide with the electrons of the converter (1), and excite high-speed electrons. The high-speed electrons and the high-pressure gas generate Cherenkov photons. The photons are reflected by the primary reflector (2) and the secondary reflector (3) in turn, pass through the pressure sealing window (4), and reach the detection surface of the detector (5); The distance between the primary reflector (2) and the secondary reflector (3) must satisfy: T1<T<T2; Wherein, T is the time taken for the gamma ray to enter the converter (1), generate Cherenkov photons, pass through the primary reflector (2), the secondary reflector (3), the pressure sealing window (4), and reach the detection surface of the detector (5); T1 is the time required for the gamma ray to pass through the converter (1), the secondary reflector (3), the pressure sealing window (4) in sequence and reach the detection surface of the detector (5); T2 is the time required for the secondary gamma rays generated by the gamma radiation to reach the detection surface of the detector (5).

2. The compact gamma-ray detection optical system according to claim 1, characterized in that: N light-blocking rings (10) are coaxially arranged in the sealed housing (11) along the gamma ray emission direction, and are used to filter out stray light, where N is a positive integer and N≥2.

3. The compact gamma-ray detection optical system according to claim 2, characterized in that: A shielding ring (6) is also provided in the sealed housing (11) for filtering out large-angle Cherenkov photons; The N light-blocking rings (10) are a first light-blocking ring, a second light-blocking ring, ... an Nth light-blocking ring, which are arranged in sequence along the gamma ray emission direction; The shielding ring (6) is located between the first light blocking ring and the second light blocking ring, and is arranged adjacent to the first light blocking ring.

4. The compact gamma-ray detection optical system according to claim 3, characterized in that: The end surface of the secondary reflector (3) close to the converter (1) is provided with a secondary mirror front shielding body (7); The end surface of the secondary reflector (3) close to the detector (5) is provided with a secondary mirror gap shielding body (8); The end surface of the primary reflector (2) close to the secondary reflector (3) is provided with a probe outer shielding body (9), which is sleeved on a sealing sleeve (16).

5. The compact gamma-ray detection optical system according to any one of claims 1 to 4, characterized in that: The distance between the primary reflector (2) and the converter (1) is 1058 mm, the distance between the secondary reflector (3) and the converter (1) is 950 mm, the distance between the pressure sealing window (4) and the converter (1) is 1009 mm, and the distance between the detection surface of the detector (5) and the converter (1) is 1027 mm.

6. The compact gamma-ray detection optical system according to claim 5, characterized in that: The spherical radius of the main reflector (2) is -383.88; The quadratic coefficient k, second-order coefficient α1, fourth-order coefficient α2, sixth-order coefficient α3, eighth-order coefficient α4, and tenth-order coefficient α5 of the primary reflector (2) are -0.355412, -2.578422×10 -4 3.238440×10 -9 , 6.868379×10 -15 ,1.380407×10 -17 , -7.828763×10 -22 ; The spherical radius of the secondary reflector (3) is 59.55; The quadratic coefficient k, second-order coefficient α1, fourth-order coefficient α2, sixth-order coefficient α3, eighth-order coefficient α4, and tenth-order coefficient α5 of the secondary reflector (3) are -3.023504, -8.155204×10 -3 ,1.295230×10 -6 , -3.302616×10 -10 8.337472×10 -14 , -1.197747×10 -17 ; The surface shapes of the primary reflector (2) and the secondary reflector (3) are both even-order aspheric surfaces, and the surface shape formula is as follows: Where: z is the sag of the reflector; c is the inverse of the spherical radius; r is the radial variable.

7. The compact gamma-ray detection optical system according to claim 1, characterized in that: The diameters of the converter (1), the primary reflector (2), the secondary reflector (3), the pressure sealing window (4) and the detection surface of the detector (5) are 70 mm, 170 mm, 80 mm, 40 mm and 10 mm respectively.

8. The compact gamma-ray detection optical system according to claim 7, characterized in that: The material of the converter (1) is beryllium, and the materials of the primary reflector (2) and the secondary reflector (3) are both aluminum; The pressure sealing window (4) is a sapphire pressure sealing window; The high pressure gas is CO2 or C2F6.

9. A compact gamma-ray detection method, based on the compact gamma-ray detection optical system according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) Gamma rays pass through the sealed housing (11) and are incident on the converter (1), colliding with electrons in the converter (1) to excite high-speed electrons; 2) The speed of high-speed electrons exceeds the speed of light in the high-pressure gas in the sealed housing (11), and the high-speed electrons and the high-pressure gas generate Cherenkov photons; 3) The primary reflector (2) and the secondary reflector (3) fold the optical path of the Cherenkov photons so that they pass through the pressure sealing window (4) and reach the detection surface of the detector (5); The distance between the primary reflector (2) and the secondary reflector (3) must satisfy: T1<T<T2; Wherein, T is the time taken for the gamma ray to enter the converter (1), generate Cherenkov photons, pass through the primary reflector (2), the secondary reflector (3), the pressure sealing window (4), and reach the detection surface of the detector (5); T1 is the time required for the gamma ray to pass through the converter (1), the secondary reflector (3), the pressure sealing window (4) in sequence and reach the detection surface of the detector (5); T2 is the time required for the secondary gamma rays generated by the gamma radiation to reach the detection surface of the detector (5); 4) The detector (5) detects the photon history of the time T that reaches the detection surface of the detector (5) in step 3) to obtain the gamma ray radiation history.

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