Rectangular coaxial vacuum Compton detector and impedance design method thereof

Abstract

The invention relates to a rectangular coaxial vacuum Compton detector and an impedance design method thereof, belongs to the technical field of pulse gamma radiation detection, and solves the technical problem that the coaxial vacuum Compton detector is complex in structural design, and the detector comprises an outer conductor, an inner conductor, a trapezoidal connecting plate, a coaxial adapter and an inner conductor support frame. The inner conductor, the trapezoidal connecting plate and the inner conductor supporting frame are located in the outer conductor, and the coaxial adapter is located outside the outer conductor. The center of the inner conductor coincides with the center of the outer conductor. And two ends of the inner conductor support frame are respectively connected with the outer conductor and the inner conductor. And the trapezoidal connecting plates are positioned at two ends of the inner conductor and are welded with the inner conductor. The impedance design method comprises the following steps: establishing a rectangular coaxial vacuum Compton detector structure parameterized model, setting boundary conditions and material parameters of the detector structure parameterized model, adjusting the width of the middle section of the inner conductor, and implementing model simulation by taking impedance parameters as a simulation target.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulsed gamma radiation detection, and particularly relates to a rectangular coaxial vacuum Compton detector and an impedance design method thereof. Background Art

[0002] In the field of pulsed gamma radiation detection, Compton detectors have been widely used in the field of intense pulsed gamma ray detection due to their characteristics such as low sensitivity, fast time response, and large dynamic range.

[0003] For vacuum Compton detectors, impedance design is a key parameter affecting their time response performance. The currently used vacuum Compton detectors often adopt single-ended output without impedance design, and the time response bandwidth is below 1 GHz@-3dB. When measuring sub-nanosecond pulsed gamma signals, large signal reflections will occur, affecting the quality of the measured waveform. With the construction and use of current pulsed gamma generation devices (such as inertial confinement fusion, synchrotron radiation devices, large pulsed reactors, etc.), the intensity of pulsed gamma rays is getting higher and higher, and the duration is getting shorter and shorter (<1 ns). The demand for high-precision detection of the time characteristics of pulsed radiation fields is increasing. Therefore, there is an urgent need to design a coaxial vacuum Compton detector to meet the detection needs.

[0004] Currently, the coaxial vacuum Compton detectors found in the literature adopt ellipsoidal or conical structures, and certain effects have been achieved in improving the time response performance. However, their internal structure design is complex, and there is no publicly disclosed impedance matching design process and method, which are not easy to promote and apply. Summary of the Invention

[0005] In order to overcome the deficiency of the complex structure design of the coaxial vacuum Compton detector and meet the high-precision measurement requirements of sub-nanosecond high-intensity pulsed gamma rays, the present invention proposes a rectangular coaxial vacuum Compton detector and an impedance design method thereof.

[0006] The technical solution adopted by the present invention to solve its technical problems is:

[0007] A rectangular coaxial vacuum Compton detector includes an outer conductor, an inner conductor, a trapezoidal connecting plate, a coaxial adapter, and an inner conductor support frame.

[0008] The inner conductor, the trapezoidal connecting plate, and the inner conductor support frame are located inside the outer conductor, and the coaxial adapter is located outside the outer conductor. The center of the inner conductor coincides with the center of the outer conductor. Both ends of the inner conductor support frame are respectively connected to the outer conductor and the inner conductor. The trapezoidal connecting plate is located at both ends of the inner conductor, and the trapezoidal connecting plate is welded to the inner conductor. The coaxial adapter is welded to the trapezoidal connecting plate.

[0009] The above-mentioned rectangular coaxial vacuum Compton detector, the outer conductor includes an outer conductor middle section and an outer conductor tapered section. The outer conductor middle section is cuboid-shaped, and the outer conductor tapered sections are located at both ends of the outer conductor middle section. The outer conductor middle section and the outer conductor tapered sections form a closed cavity. The outer conductor middle section includes a ray incident surface, side surfaces, and an outer conductor bottom surface, and the side surfaces are respectively connected to the ray incident surface and the outer conductor bottom surface.

[0010] The inner conductor includes a connected inner conductor middle section and inner conductor tapered sections. The inner conductor middle section is cuboid-shaped, and the inner conductor tapered sections are trapezoidal and located at both ends of the inner conductor middle section.

[0011] The inner conductor middle section is parallel to the ray incident surface and the outer conductor bottom surface.

[0012] The above-mentioned rectangular coaxial vacuum Compton detector, the outer conductor and the inner conductor are both made of conductive metal materials. The thickness of the outer conductor is 1 mm to 5 mm, and the thickness of the inner conductor is 1 mm to 3 mm.

[0013] The above-mentioned rectangular coaxial vacuum Compton detector, the thickness of the trapezoidal connecting plate is the same as that of the inner conductor. The width of the lower bottom edge of the trapezoidal connecting plate is the same as the width v of the side connected to the inner conductor. The upper bottom surface is welded to the inner core of the coaxial adapter. The width of the upper bottom edge is 1 mm to 1.5 mm, and the height of the trapezoidal connecting plate is 1 mm to 3 mm.

[0014] The above-mentioned rectangular coaxial vacuum Compton detector, the inner conductor support frame is made of polyethylene material and is placed at the four corners of the inner conductor. It is a cylinder with a diameter of 5 mm, and both ends of the cylinder are adhesively connected to the inner conductor middle section and the outer conductor bottom surface respectively.

[0015] The above-mentioned rectangular coaxial vacuum Compton detector, the outer conductor bottom surface, the side surfaces and the outer conductor tapered sections are made of stainless steel and are conductive, and their thicknesses are all 3 mm.

[0016] The above-mentioned rectangular coaxial vacuum Compton detector, the ray incident surface is made of aluminum alloy with a thickness of 1 mm.

[0017] The above-mentioned rectangular coaxial vacuum Compton detector, the length L0 of the outer conductor middle section = 76.5 mm, the width a = 76.5 mm, and the height b = 45 mm;

[0018] The length L1 of the outer conductor tapered section = 30.75 mm, the width a1 = 20 mm, and the height b1 = 14 mm;

[0019] The width w of the inner conductor middle section = 54 mm, the length is 76.5 mm, and the thickness is 1 mm;

[0020] The width v of the inner conductor tapered section is 16 mm, the length is 27.75 mm, and the thickness is 1 mm;

[0021] The thickness t1 of the trapezoidal connecting plate is 1 mm, the width is 1.3 mm, and the height is 3 mm.

[0022] For the above rectangular coaxial vacuum Compton detector, two coaxial adapters are provided, one of which is connected to the coaxial matching head for end impedance matching; the other is connected to an oscilloscope through a coaxial cable for outputting detector signals.

[0023] A method for impedance design of a rectangular coaxial vacuum Compton detector includes the following steps:

[0024] Step S1: Using a three-dimensional electromagnetic simulation software, based on the structural parameters of the rectangular coaxial vacuum Compton detector, establish a parametric model of the rectangular coaxial vacuum Compton detector structure;

[0025] Step S2: Set the boundary conditions and material parameters of the detector parametric model. The background material is vacuum. Set the end face of the coaxial adapter as a waveguide port, and the boundary conditions are set as open boundaries;

[0026] Step S3: Adjust the width w of the middle section of the inner conductor. Using the impedance parameter as the simulation target, perform model simulation until the impedance of the middle section of the inner conductor meets the design requirements.

[0027] The beneficial effects of the present invention are:

[0028] For a rectangular coaxial vacuum Compton detector, through coaxial matching design of the inner and outer conductors and connecting coaxial lines at both ends of the inner conductor for output, the impedance of the signal during transmission on the emitter is as close as possible to 50 ohms, reducing the influence of standing waves and reflected signals, improving the quality of the detector output signal, and enhancing the response bandwidth of the detector to meet the high-precision measurement requirements of sub-nanosecond high-intensity pulsed gamma rays.

[0029] A method for impedance design of a rectangular coaxial vacuum Compton detector. The designed vacuum Compton detector has a response bandwidth of up to 3.5 GHz @ -3 dB and can be used for high-precision measurement of the characteristic parameters of sub-nanosecond high-intensity pulsed gamma radiation fields. Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the structure of the vacuum Compton detector in Embodiment 2 of the present invention;

[0031] Figure 2 It is a top view of the structure of the vacuum Compton detector in Embodiment 2 of the present invention;

[0032] Figure 3It is the front view of the vacuum Compton detector structure in Embodiment 2 of the present invention;

[0033] Figure 4 It is the side view of the vacuum Compton detector structure in Embodiment 2 of the present invention;

[0034] Figure 5 It is the CST simulation model diagram;

[0035] Figure 6 It is the relationship diagram between the inner conductor width w and the characteristic impedance Z1 of the middle section;

[0036] Figure 7 It is the relationship between the width v of the end of the inner conductor of the present invention and the overall characteristic impedance Z0;

[0037] Figure 8 It is the structure of the commonly used VCD without impedance matching design at present;

[0038] Figure 9 It is the impedance curve of the VCD without impedance matching design;

[0039] Figure 10 It is the comparison diagram of the time response simulation curves of the vacuum type Compton detector without impedance matching design and the vacuum type Compton detector designed by the present invention;

[0040] Figure 11 It is the simulation result of the response bandwidth of the vacuum Compton detector in Embodiment 2 of the present invention.

[0041] Reference numerals: 1. Outer conductor, 2. Inner conductor, 3. Trapezoidal connecting plate, 4. Coaxial adapter, 5. Inner conductor support frame, 11. Middle section of the outer conductor, 12. Tapered section of the outer conductor, 111. Ray incident surface, 112. Bottom surface of the outer conductor, 113. Side surface, 21. Middle section of the inner conductor, 22. Tapered section of the inner conductor, 31. Incident window, 32. Emitter, 33. Exit window, 34. Cylindrical side wall, 35. Insulating support frame, 36. Metal wire, 37. Coaxial cable, 38. Matching resistor. Detailed implementation manners

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Embodiment 1

[0044] A rectangular coaxial vacuum Compton detector, comprising an outer conductor 1, an inner conductor 2, a trapezoidal connecting plate 3, a coaxial adapter 4, and an inner conductor support frame 5. The outer conductor 1 consists of a cuboid-shaped outer conductor middle section 11 and outer conductor tapered sections 12 at both ends, forming a closed chamber. The outer conductor middle section 11 includes a radiation incident surface 111 and a bottom surface 112. The inner conductor 2 includes a rectangular inner conductor middle section 21 and trapezoidal inner conductor tapered sections 22 at both ends; the inner and outer conductor structures of the tapered sections at both ends are symmetrical.

[0045] The outer conductor 1 is made of a conductive metal material, generally stainless steel or aluminum, with a thickness of 1 - 5 mm.

[0046] The inner conductor 2 is made of a conductive metal material, generally stainless steel or aluminum, with a thickness of 1 - 3 mm.

[0047] The rectangular surface of the inner conductor 2 is placed parallel to the outer conductor middle section, and the center of the inner conductor 2 coincides with the center of the outer conductor 1.

[0048] The length of the inner conductor middle section 21 is the same as the length L0 of the outer conductor middle section 11, and the value range is 75 mm - 150 mm.

[0049] The width a of the outer conductor middle section is equal to L0, and the height b ranges from 1 / 2 to 2 / 3 of the width a.

[0050] The length L1 of the outer conductor tapered section ranges from 1 / 2 to 2 / 3 of the length L0, and the width a1 and height b1 at the end of the outer conductor tapered section are between 12 mm and 30 mm.

[0051] The length L2 of the inner conductor tapered section 22 plus the length L3 of the trapezoidal connecting plate 3 is equal to the length L1 of the outer conductor tapered section 12.

[0052] The coaxial adapter 4 is welded to the side surface at the end of the outer conductor tapered section 12. The diameter of the adapter is less than 10 mm. The outer shell of the coaxial adapter 4 is welded to the outer conductor tapered section 12, and the inner core is flush with the inner end surface of the side surface at the end of the outer conductor tapered section 12.

[0053] The thickness t1 of the trapezoidal connecting plate 3 is the same as the thickness t of the inner conductor. The lower bottom surface is welded to the side surface of the inner conductor 2, and the width is the same as the width v of the inner conductor. The upper bottom surface is welded to the inner core of the coaxial adapter 4, and the width is 1 mm - 1.5 mm. The length (height) of the trapezoidal connecting plate is 1 mm - 3 mm.

[0054] The material of the inner conductor support frame 5 is a cylindrical polyethylene material, which is placed at the four corners of the inner conductor, with a diameter of about 5 mm. The two ends of the cylindrical surface are adhesively bonded to the inner conductor middle section 21 and the outer conductor bottom surface 112 respectively.

[0055] The coaxial matching head is connected to one of the coaxial adapters, which plays the role of terminal impedance matching. The other coaxial adapter serves as the detector signal output port and is generally connected to an oscilloscope through a coaxial cable. The two coaxial adapters can be interchanged as the detector signal output port.

[0056] A method for impedance design of a rectangular coaxial vacuum Compton detector includes the following steps:

[0057] Select the width a, height b, and length L0 of the middle section 11 of the outer conductor.

[0058] Select the length L1 of the tapered section 12 of the outer conductor and the width a1 and height b1 at the end of the tapered section 12 of the outer conductor.

[0059] Select the thickness of the inner conductor, with a range of 1 - 3 mm.

[0060] Establish a parametric model of the detector structure.

[0061] Set the boundary conditions and material parameters. The materials of the inner and outer conductors are PEC materials, the background material is vacuum, set the end face of the adapter as a waveguide port, and set the boundary condition as an open boundary.

[0062] By adjusting the width w of the middle section 21 of the inner conductor, with the impedance parameter as the simulation target, until the impedance parameter curve of the middle section meets 50 ohms ± 1 ohm.

[0063] By adjusting the width v of the tapered section 22 of the inner conductor, with the impedance parameter as the simulation target, until the impedance parameter curve of the tapered section meets 50 ohms ± 3 ohms.

[0064] Embodiment 2

[0065] A rectangular coaxial vacuum Compton detector and its impedance design method. As Figures 1 to 4 Shown is a vacuum Compton detector with a rectangular coaxial structure, including an outer conductor 1, an inner conductor 2, a trapezoidal connecting plate 3, a coaxial adapter 4, and an inner conductor support frame 5. The outer conductor 1 includes a cuboid-shaped middle section 11 of the outer conductor and tapered sections 12 of the outer conductor at both ends. The middle section 11 of the outer conductor and the tapered sections 12 of the outer conductor form a closed chamber. The middle section 11 of the outer conductor includes a ray incident surface 111, a bottom surface 112, and a side surface 113. The inner conductor 2 includes a rectangular middle section 21 of the inner conductor and trapezoidal tapered sections 22 of the inner conductor at both ends; the inner and outer conductor structures at both ends are symmetrical;

[0066] The bottom surface 112 and side surface 113 of the middle section of the outer conductor and the tapered section 12 of the outer conductor are made of conductive metal material, which is stainless steel material with a thickness of 3 mm;

[0067] The ray incident surface 111 of the outer conductor is made of conductive metal material, which is aluminum material with a thickness of 1 mm;

[0068] The inner conductor 2 is made of conductive metal material, which is stainless steel with a thickness of 1 mm;

[0069] The inner conductor 2 is placed parallel to the middle section 11 of the outer conductor, and the center of the inner conductor 2 coincides with the center of the outer conductor 1;

[0070] The length L0 of the middle section 11 of the outer conductor is 76.5 mm, the width a is 76.5 mm, and the height b is 45 mm;

[0071] The length L1 of the tapered section 12 of the outer conductor is 30.75 mm, the width a1 is 20 mm, and the height b1 is 14 mm;

[0072] The width w of the middle section 21 of the inner conductor is 54 mm, the length L0 is 76.5 mm, and the thickness is 1 mm;

[0073] The width v of the tapered section 22 of the inner conductor is 16 mm, the length L2 is 27.75 mm, and the thickness is 1 mm.

[0074] The trapezoidal connecting plate 3 has a thickness of 1 mm. The lower bottom surface is welded to the side surface of the inner conductor 2, and the width is the same as the width v of the inner conductor. The upper bottom surface is welded to the inner core of the coaxial adapter 4, and the width is 1.3 mm. The length (height) of the trapezoidal connecting plate is 3 mm.

[0075] Figure 6 It is a relationship diagram between the width w of the middle section of the inner conductor and the characteristic impedance Z1 of the middle section in this invention patent. Since the length, width, and height of the middle section of the outer conductor are determined, and the thickness of the inner conductor is 1 mm, then it is necessary to find the width w of the middle section of the inner conductor when the impedance of the middle section is matched.

[0076] The characteristic impedance of the rectangular coaxial line is approximately

[0077]

[0078] ε0: magnetic permeability;

[0079] μ0: permittivity;

[0080] η0: characteristic impedance of free space, 120π ohms;

[0081] C0: distributed capacitance per unit length, F / m;

[0082] The approximate expression of the distributed capacitance per unit length is

[0083]

[0084] From the formula, by setting Z1 = 50 ohms, it can be calculated that w is approximately 56.5 mm.

[0085] The above approximate expression does not consider the influence of the inner conductor thickness. To achieve better impedance matching, the exact value of w needs to be obtained. Therefore, a model of the middle section between the inner and outer conductors is established in a 3D electromagnetic simulation software. The width w of the middle section of the inner conductor is set as a variable, and w is swept within the range of 50 mm - 60 mm. The relationship diagram between w and the characteristic impedance Z1 of the middle section of the detector can be obtained. As Figure 6 shown, when w = 54 mm, the characteristic impedance Z1 = 50 ohms.

[0086] Figure 7 This is the relationship between the width v of the end of the inner conductor of this invention patent and the overall characteristic impedance Z0. The width v of the end of the tapered section of the inner conductor is set as a variable, and v is swept within the range of 10 mm - 20 mm. The relationship diagram between v and the characteristic impedance Z of the detector can be obtained. When v = 15 - 18 mm, the characteristic impedance of the detector satisfies Z0 = 50 ohms ± 3 ohms.

[0087] Figure 8 and Figure 9 are the structure and impedance curve of a VCD without impedance matching design;

[0088] Figure 10 is the comparison of the time response curve of a VCD without impedance matching design and the design of this invention (when v takes the value of 16 mm) with the time waveform of the input electron beam. When simulating the output signal curve of the detector when the electron beam is incident using CTS - PS from the incident window, the time characteristics of the electron beam adopt a Gaussian distribution (standard deviation sigma = 0.2, waveform half - width FWHM = 2.3548×sigma = 0.47 ns), which characterizes the incident situation of sub - nanosecond pulses. It can be seen that the time response characteristics of the VCD detector designed by this invention have been greatly improved compared with the detector without impedance matching design.

[0089] Figure 11 The simulation results of the S12 parameter of the detector show that the response bandwidth of the detector reaches 3.5 GHz @ - 3 dB, which can meet the high - precision measurement requirements of the characteristic parameters of the sub - nanosecond pulse gamma radiation field.

[0090] Embodiment 3

[0091] A method for impedance design of a rectangular coaxial vacuum Compton detector includes the following steps:

[0092] Step S1, establish a parametric model of the structure of a rectangular coaxial vacuum Compton detector in a 3D electromagnetic simulation software.

[0093] Step S2, set the boundary conditions and material parameters. The materials of the inner and outer conductors are PEC materials, the background material is vacuum, the end face of the adapter is set as a waveguide port, and the boundary condition is set as an open boundary.

[0094] Step S3: By adjusting the width w of the middle section 21 of the inner conductor, with the impedance parameter as the simulation target, until the impedance parameter curve of the middle section 21 of the inner conductor meets 50 ohms ± 1 ohm.

Claims

1. A rectangular coaxial vacuum Compton detector, characterized in that It includes an outer conductor (1), an inner conductor (2), a trapezoidal connecting plate (3), a coaxial adapter (4), and an inner conductor support frame (5); The inner conductor (2), the trapezoidal connecting plate (3), and the inner conductor support frame (5) are located inside the outer conductor (1), and the coaxial adapter (4) is located outside the outer conductor (1); the center of the inner conductor (2) coincides with the center of the outer conductor (1); both ends of the inner conductor support frame (5) are respectively connected to the outer conductor (1) and the inner conductor (2); the trapezoidal connecting plate (3) is located at both ends of the inner conductor (2), and the trapezoidal connecting plate (3) is welded to the inner conductor (2); the coaxial adapter (4) is welded to the trapezoidal connecting plate (3).

2. The rectangular coaxial vacuum Compton detector according to claim 1, wherein The outer conductor (1) includes an outer conductor middle section (11) and an outer conductor tapered section (12). The outer conductor middle section (11) is rectangular parallelepiped-shaped, and the outer conductor tapered section (12) is located at both ends of the outer conductor middle section (11). The outer conductor middle section (11) and the outer conductor tapered section (12) form a closed cavity; the outer conductor middle section (11) includes a ray incident surface (111), a side surface (113), and an outer conductor bottom surface (112), and the side surface (113) is respectively connected to the ray incident surface (111) and the outer conductor bottom surface (112); The inner conductor (2) includes a connected inner conductor middle section (21) and an inner conductor tapered section (22). The inner conductor middle section (21) is rectangular parallelepiped-shaped, and the inner conductor tapered section (22) is trapezoidal and is located at both ends of the inner conductor middle section (21); The inner conductor middle section (21) is parallel to the ray incident surface (111) and the outer conductor bottom surface (112).

3. The rectangular coaxial vacuum Compton detector according to claim 1, wherein Both the outer conductor (1) and the inner conductor (2) are made of conductive metal materials. The thickness of the outer conductor (1) is 1 mm to 5 mm, and the thickness of the inner conductor (2) is 1 mm to 3 mm.

4. The rectangular coaxial vacuum Compton detector according to claim 1, wherein The thickness of the trapezoidal connecting plate (3) is the same as that of the inner conductor (2). The width of the lower bottom edge of the trapezoidal connecting plate (3) is the same as the width v of the connecting edge with the inner conductor (2). The upper bottom surface is welded to the inner core of the coaxial adapter (4). The width of the upper bottom edge is 1 mm to 1.5 mm, and the height of the trapezoidal connecting plate (3) is 1 mm to 3 mm.

5. The rectangular coaxial vacuum Compton detector according to claim 2, characterized in that, The material of the inner conductor support frame (5) is polyethylene material. It is placed at the four corners of the inner conductor (2) and is a cylinder. The diameter of the cylinder is 5 mm, and both ends of the cylinder are adhesively connected to the inner conductor middle section (21) and the outer conductor bottom surface (112) respectively.

6. The rectangular coaxial vacuum Compton detector according to claim 2, characterized in that, The outer conductor bottom surface (112), the side surface (113), and the outer conductor tapered section (12) are made of stainless steel and are conductive, and their thicknesses are all 3 mm.

7. The rectangular coaxial vacuum Compton detector according to claim 2, wherein The ray incident surface (111) is made of aluminum alloy, and its thickness is 1 mm.

8. The rectangular coaxial type vacuum Compton detector according to claim 2, wherein The length L0 of the outer conductor middle section (11) is 76.5 mm, the width a is 76.5 mm, and the height b is 45 mm; The length L1 of the outer conductor tapered section (12) is 30.75 mm, the width a1 is 20 mm, and the height b1 is 14 mm; The width w of the inner conductor middle section (21) is 54 mm, the length is 76.5 mm, and the thickness is 1 mm; The width v of the inner conductor tapered section (22) is 16 mm, the length is 27.75 mm, and the thickness is 1 mm; The thickness of the trapezoidal connecting plate (3) is 1 mm, the width is 1.3 mm, and the height is 3 mm.

9. The rectangular coaxial vacuum Compton detector according to claim 1, characterized in that, Two coaxial adapters (4) are provided, one of which is connected to a coaxial matching head for end impedance matching; the other is connected to an oscilloscope through a coaxial cable for outputting detector signals.

10. A method for impedance design of a rectangular coaxial vacuum Compton detector, characterized in that, It includes the following steps: Step S1: Using a three-dimensional electromagnetic simulation software, based on the structural parameters of the rectangular coaxial vacuum Compton detector, establish a parametric model of the rectangular coaxial vacuum Compton detector structure; Step S2: Set the boundary conditions and material parameters of the detector parametric model. The background material is vacuum. Set the end face of the coaxial adapter (4) as a waveguide port, and set the boundary conditions as open boundaries; Step S3: Adjust the width of the middle section (21) of the inner conductor. Taking the impedance parameter as the simulation target, perform model simulation until the impedance of the middle section (21) of the inner conductor meets the design requirements.

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