Intensive radiation background photoelectron signal extraction device, system and method

Abstract

The invention relates to the field of optoelectronic signal extraction, in particular to an intense radiation background optoelectronic signal extraction device, system and method. The device comprises a photoelectric cathode, an accelerating electrode, a focusing device and an MCP detector, the photoelectric cathode is a planar photoelectric cathode; the accelerating electrode is a superfine grid mesh type plane accelerating electrode; the focusing device is of a solenoid structure bent by a 1 / 4 arc; the MCP detector is a micro-channel plate type image intensifier; the photoelectric cathode, the accelerating electrode, the focusing device and the MCP detector are sequentially connected through ceramic rings. The motion direction of photoelectron signals output by the photoelectric cathode is changed by adopting the solenoid structure bent by a 1 / 4 arc, X-ray signals which are in the same time and empty as high-energy neutron signals can be converted into the photoelectron signals through the photoelectric cathode and then deflected to the MCP detector by a certain angle, spatial separation of the X-ray signals and the high-energy neutron signals is achieved, and the detection accuracy is improved. The detection signal-to-noise ratio is improved, and meanwhile, components such as an MCP detector which are easily damaged by radiation of high-energy neutron signals are protected.

Description

Technical Field

[0001] The invention relates to a photoelectron signal extraction device, and in particular to a device, system and method for extracting photoelectron signals from a strong radiation background. Background Art

[0002] Large scientific facilities such as large laser devices and high-energy ion beam devices will produce X-ray signals and high-energy neutron signals while producing high-energy density materials. The X-ray signals directly reflect the various information parameters of the high-energy density materials and need to be detected quickly and directly.

[0003] MCP (microchannel plate) detectors have the advantages of fast response time, large dynamic range, high signal gain, and direct detection. They can be used to detect X-ray signals emitted instantly by high-energy density materials and diagnose their various parameters. However, the high-energy neutron signals generated along with the X-ray signals are synchronized in time and co-located in space with the X-ray signals. Since the cathode and MCP components on the MCP detector can respond to high-energy neutron signals, the high-energy neutron signals will produce secondary radiation and related effects after interacting with the materials of the MCP detector. The high background and high noise generated by these high-energy neutron signals not only affect the signal-to-noise ratio of the MCP detector, but also easily cause permanent damage to the MCP detector itself.

[0004] At present, the shielding technology for harmful neutron radiation has been developed to a certain extent, but there has been no relevant research and reports in the field of extracting photoelectron signals generated by X-ray signals at the same time and position as high-energy neutron signals. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems of low signal-to-noise ratio and short life of the existing MCP detector under high-energy neutron radiation background, and to provide a strong radiation background photoelectron signal extraction device, system and method.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: A strong radiation background photoelectron signal extraction device, comprising a photocathode, an accelerating electrode, a focusing device and an MCP detector; The photocathode is used to convert external optical radiation signals into photoelectron signals; the accelerating electrode is used to accelerate the photoelectron signals; the focusing device is used to focus and adjust the trajectory of the photoelectron signals; the MCP detector is used to collect the focused photoelectron signals and multiply them; Its special features are: The photocathode is a planar photocathode; The accelerating electrode is an ultra-fine grid type planar accelerating electrode, the diameter of which is equal to the diameter of the photocathode, and the accelerating electrode is placed parallel to the photocathode; The focusing device is a solenoid structure with a 1 / 4 arc bend, the outer diameter of the inlet end face of the focusing device is equal to the diameter of the photocathode; the outlet end face of the focusing device is perpendicular to the inlet end face; the inlet end face of the focusing device faces the accelerating electrode, and the outlet end face faces the MCP detector; The MCP detector is a microchannel plate image intensifier, and the input port diameter of the MCP detector is equal to the inner diameter of the outlet end face of the focusing device; or the input port diameter of the MCP detector is larger than the inner diameter of the outlet end face of the focusing device; The MCP detector and the photocathode are arranged perpendicular to each other; The photocathode, the accelerating electrode, the focusing device and the MCP detector are connected in sequence through ceramic rings.

[0007] Furthermore, the focusing device includes a cylindrical hollow iron shell bent in a 1 / 4 arc, and a spiral coil wound on the hollow iron shell; The two ends of the coil are connected to an external power source respectively; the two ends of the hollow iron shell are connected to the accelerating electrode and the MCP detector respectively through ceramic rings; The inner diameter of the hollow iron shell is 35mm~45mm, the outer diameter is 45mm~55mm, the thickness is 5mm, the radius of curvature is 150mm~200mm, the length along the optical axis is 150mm~200mm, the distance between the entrance end face of the hollow iron shell and the accelerating electrode is 30mm~45mm, and the distance between the exit end face and the input port of the MCP detector is 100mm~120mm; the number of coil turns is 100~400.

[0008] Furthermore, the potential difference between the accelerating electrode and the photocathode is 500V~2000V. The diameter of the photocathode is 45mm~55mm, and the dimension of the photocathode along the optical axis is 0.1mm~0.5mm. The diameter of the accelerating electrode is 45mm~55mm, and the dimension along the optical axis is 0.1mm~0.5mm; the spacing between the accelerating electrode and the photocathode is 1mm~3mm.

[0009] The current intensity of the focusing device is 10A~250A.

[0010] The potential difference between the MCP detector and the accelerating electrode is 10 V to 1000 V. The diameter of the MCP detector is 40 mm to 80 mm, and the thickness is 0.2 mm to 0.5 mm.

[0011] The present invention also provides a strong radiation background light electronic signal extraction system, which is special in that it comprises the above-mentioned strong radiation background light electronic signal extraction device.

[0012] At the same time, the present invention also provides a method for extracting strong radiation background photoelectron signals, based on the above-mentioned strong radiation background photoelectron signal extraction device, which is special in that it includes the following steps: Step 1: converting the received external optical radiation signal into a photoelectron signal through the photocathode and outputting it to the accelerating electrode; Step 2, accelerating the photoelectron signal through the accelerating electrode and then outputting it to the entrance end face of the focusing device; Step 3, focusing the photoelectron signal through a focusing device, bending its running trajectory by 1 / 4 arc, and then outputting it to the MCP detector through its exit end face; Step 4: The focused photoelectron signal is collected and multiplied by the MCP detector to complete the extraction of the strong radiation background photoelectron signal.

[0013] The beneficial effects of the present invention are: The present invention adopts a 1 / 4 arc bent solenoid structure to change the running direction of the photoelectron signal output by the photocathode, and can convert the X-ray signal at the same time and position as the high-energy neutron signal into a photoelectron signal through the photocathode, and then deflect it at a certain angle and output it to the MCP detector, thereby realizing spatial separation of the X-ray signal and the high-energy neutron signal, improving the detection signal-to-noise ratio, and protecting the components such as the MCP detector that are easily damaged by the radiation of the high-energy neutron signal, thereby increasing the service life of the MCP detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the structure of an embodiment of a strong radiation background photoelectron signal extraction device of the present invention (the ceramic ring is not shown); Figure 2 It is a schematic structural diagram of a focusing device in an embodiment of a strong radiation background photoelectron signal extraction device of the present invention; Figure 3 It is an equipotential line distribution diagram of an embodiment of a strong radiation background photoelectron signal extraction device of the present invention; Figure 4 A magnetic field intensity distribution diagram of an embodiment of a strong radiation background photoelectron signal extraction device of the present invention; Figure 5 A schematic diagram of the running trajectory of the photoelectron signal of the photocathode in an embodiment of a strong radiation background photoelectron signal extraction device of the present invention; Figure 6 This is a schematic diagram of the spatial distribution of photoelectrons near the photocathode in an embodiment of a strong radiation background photoelectron signal extraction device of the present invention; Figure 7 This is a schematic diagram of the spatial distribution of photoelectrons at the input end face of an MCP detector in an embodiment of a strong radiation background photoelectron signal extraction device of the present invention; The reference numerals in the figure are: 1-photocathode, 2-accelerating electrode, 3-focusing device, 31-hollow iron shell, 32-coil; 4-MCP detector. DETAILED DESCRIPTION

[0015] In order to make the purpose, advantages and features of the present invention clearer, the following is a further detailed description of a strong radiation background photoelectron signal extraction device, system and method proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following specific implementation methods, the advantages and features of the present invention will be clearer.

[0016] See also Figure 1 The structure of a strong radiation background photoelectron signal extraction device in this embodiment mainly includes a photocathode 1, an accelerating electrode 2, a focusing device 3 and an MCP detector 4.

[0017] Among them, the main function of the photocathode 1 is to convert the external optical radiation signal into a photoelectron signal. In the present embodiment, the photocathode 1 is specifically a planar photocathode, and the diameter of the photocathode 1 is 45mm~55mm, and 50mm can be selected; the size of the photocathode 1 along the length direction of the optical axis is 0.1mm~0.5mm, and 0.5mm can be selected.

[0018] The main function of the accelerating electrode 2 is to accelerate the photoelectron signal output by the photocathode 1. In this embodiment, the accelerating electrode 2 is specifically an ultra-fine grid type planar accelerating electrode. The accelerating electrode 2 is placed parallel to the photocathode 1. The spacing between the accelerating electrode 2 and the photocathode 1 is 1mm~3mm, and 1.5mm can be selected. The accelerating electrode 2 and the photocathode 1 are connected by a ceramic ring. The diameter of the accelerating electrode 2 is 45mm~55mm. In this embodiment, the diameter of the accelerating electrode 2 is equal to the diameter of the photocathode 1, so 50mm can be selected. The size of the accelerating electrode 2 along the optical axis direction is 0.1mm~0.5mm, and 0.5mm can be selected. The potential difference between the accelerating electrode 2 and the photocathode 1 is 500V~2000V, and 1000V can be selected.

[0019] See also Figure 1 and Figure 2 The focusing device 3 is a solenoid structure with a quarter arc bend, that is, a 90° arc bend. Specifically, the focusing device 3 includes a cylindrical hollow iron shell 31 with a quarter arc bend, and a spiral coil 32 wound on the hollow iron shell 31; both ends of the coil 32 are respectively connected to an external power supply, and a current is applied to the coil 32 through the external power supply, thereby generating an electromagnetic field.

[0020] The outer diameter of the entrance end face of the hollow iron shell 31 is equal to the diameter of the photocathode 1, and the inner diameter can be adjusted within a set range; the exit end face of the hollow iron shell 31 is perpendicular to the entrance end face; the entrance end face of the hollow iron shell 31 faces the accelerating electrode 2, and the exit end face faces the MCP detector 4. The hollow iron shell 31 is connected to the accelerating electrode 2 through a ceramic ring.

[0021] The current intensity of the coil 32 is 10A~250A, and 200A is optional; the inner diameter of the hollow iron shell 31 is 35mm~45mm, and 40mm is optional; the outer diameter of the hollow iron shell 31 is 45mm~55mm, and 50mm is optional; the thickness of the hollow iron shell 31 is 5mm; the curvature radius of the hollow iron shell 31 is 150mm~200mm, and 175mm is optional; the length of the hollow iron shell 31 along the optical axis is 150mm~200mm, and 175mm is optional; the distance between the entrance end face of the hollow iron shell 31 and the accelerating electrode 2 is 30mm~45mm, and 40mm is optional. The number of turns of the coil 32 is 100~400, and 200 is optional.

[0022] The MCP detector 4 is a microchannel plate image intensifier, and the input port diameter of the MCP detector 4 is equal to the inner diameter of the outlet end face of the hollow iron shell 31; or, the input port diameter of the MCP detector is slightly larger than the inner diameter of the outlet end face of the hollow iron shell 31, and the difference between the two sizes meets the preset difference requirement, and the preset difference requirement can be set according to experience or actual needs, and is not specifically limited in this embodiment. The MCP detector 4 is connected to the hollow iron shell 31 through a ceramic ring.

[0023] The potential difference between the MCP detector 4 and the accelerating electrode 2 is 10V~1000V, and 300V is optional; the diameter of the MCP detector 4 is 40mm~80mm, and the thickness is 0.2mm~0.5mm; the distance between the input port of the MCP detector 4 and the outlet end face of the hollow iron shell 31 is 100mm~120mm, and 105mm is optional.

[0024] The specific working process of the present invention is: Step 1: When an external optical radiation signal is input to the photocathode 1, according to Stoletov's law and Einstein's law, the inner surface of the photocathode 1 will emit photoelectrons to form a photoelectron signal. The photoelectron signal can be regarded as a replica of the external optical radiation signal, and the temporal and spatial distribution and quantity distribution of the photoelectron signal are in a certain proportional relationship with the incident optical radiation signal.

[0025] Step 2: Under the action of the accelerating electrode 2 , the photoelectron signal is accelerated and enters the focusing device 3 .

[0026] Step 3: Under the action of the electromagnetic field generated by the focusing device 3, the trajectory of the photoelectron signal is bent by 90° and incident on the MCP detector 4.

[0027] Step 4: The number of photoelectron signals is multiplied by the MCP detector 4, so that the influence of high-energy neutron signals on the detector performance index can be weakened, and the strong radiation background photoelectron signal extraction can be realized.

[0028] The effective detection area of ​​the photocathode 1 of the strong radiation background photoelectron signal extraction device is evaluated by the following process: First, a three-dimensional model of the strong radiation background photoelectron signal extraction device is established in the three-dimensional electromagnetic simulation software, and the electromagnetic field distribution inside the device is calculated. Figures 3 to 5 , with the yz perspective as a reference, the segmented integration method is used to establish the three-dimensional model of the focusing device 3, and the 1 / 4 arc bent solenoid structure is equivalent to 10 cylindrical solenoid structures with exactly the same structure. The total length of the 10 cylindrical solenoid structures is equal to the length of the 1 / 4 arc bent solenoid, and the electromagnetic field generated by the 10 cylindrical solenoid structures is the same as the electromagnetic field intensity generated by the 1 / 4 arc bent solenoid. The solution accuracy of the electromagnetic field is related to the grid accuracy of the model division. The higher the grid accuracy, the higher the solution accuracy of the electromagnetic field, but the longer the simulation time. In order to balance the solution accuracy of the electromagnetic field and the simulation time, the grid is encrypted at a certain area in the center of the model (at the trajectory of the photoelectron signal) so that the solution of the electromagnetic field represents the real electromagnetic field distribution of the model as much as possible.

[0029] Secondly, according to the electromagnetic field distribution, the trajectory of the particle in the electromagnetic field is tracked. The prerequisite for tracking the trajectory of the particle is to set the electron source reasonably. In the simulation, the photoelectron signal emitted by the photocathode 1 is sampled using the Monte Carlo method, and the initial energy of the electron source is obtained to obey the β(1,4) distribution on 0~0.6eV; the azimuth angle obeys the uniform distribution in the range of 0~2π; the pitch angle obeys the cosine distribution on 0~π / 2; and the initial position obeys the uniform distribution. According to the electromagnetic field distribution characteristics, the trajectory of the photoelectron signal in the model is calculated.

[0030] Finally, the simulation calculates the effective detection area of ​​photocathode 1 and the dispersion of photoelectron transit time. When calculating the effective detection area of ​​photocathode 1, photocathode 1 emits photoelectron signals within the range of Φ40mm, and the two-dimensional spatial (xy and xz) distribution of the photoelectron signals is monitored on the MCP detector 4, as shown in Figure 6 , Figure 7As shown. Based on the distance from the center position of the MCP detector 4 and the uniformity of the distribution of the photoelectron beam spot, it is determined that the effective detection area of ​​the photocathode 1 is greater than Φ40mm; in order to avoid current saturation in the MCP detector 4, the magnification of the strong radiation background photoelectron signal extraction device is set to 2. When calculating the transit time of the photoelectron signal, the photoelectron signal is emitted within the entire range of Φ40mm, and the time distribution of the photoelectron signal arriving at the MCP detector 4 is counted, and the half-height width of the distribution function is taken as the time dispersion. The time dispersion of the strong radiation background photoelectron signal extraction device is less than 1ns, the magnification is adjustable, and the photoelectron signal is evenly distributed when it runs to the MCP detector 4.

Claims

1. A device for extracting photoelectron signals from a strong radiation background, comprising a photocathode (1), an accelerating electrode (2), a focusing device (3) and an MCP detector (4); The photocathode (1) is used to convert external optical radiation signals into photoelectron signals; the accelerating electrode (2) is used to accelerate the photoelectron signals; the focusing device (3) is used to focus and adjust the running trajectory of the photoelectron signals; the MCP detector (5) is used to collect the focused photoelectron signals and multiply them; Features: The photocathode (1) is a planar photocathode; The accelerating electrode (2) is an ultra-fine grid type planar accelerating electrode, the diameter of which is equal to the diameter of the photocathode (1), and the accelerating electrode (2) is placed parallel to the photocathode (1); The focusing device (3) is a solenoid structure with a quarter arc bend; the outer diameter of the entrance end face of the focusing device (3) is equal to the diameter of the photocathode (1); the exit end face of the focusing device (3) and the entrance end face are perpendicular to each other; the entrance end face of the focusing device (3) faces the accelerating electrode (2), and the exit end face faces the MCP detector (4); The MCP detector (4) is a microchannel plate type image intensifier, and the diameter of the input port of the MCP detector (4) is equal to the inner diameter of the outlet end face of the focusing device (3); or the diameter of the input port of the MCP detector (4) is greater than the inner diameter of the outlet end face of the focusing device (3); The MCP detector (4) and the photocathode (1) are arranged perpendicular to each other; The photocathode (1), the accelerating electrode (2), the focusing device (3) and the MCP detector (4) are connected in sequence via ceramic rings.

2. The strong radiation background light electronic signal extraction device according to claim 1, characterized in that: The focusing device (3) comprises a cylindrical hollow iron shell (31) bent into a quarter arc, and a spiral coil (32) wound around the hollow iron shell (31); The two ends of the coil (32) are respectively connected to an external power source; the two ends of the hollow iron shell (31) are respectively connected to an accelerating electrode (2) and an MCP detector (4) via ceramic rings; The inner diameter of the hollow iron shell (31) is 35 mm to 45 mm, the outer diameter is 45 mm to 55 mm, the thickness is 5 mm, the radius of curvature is 150 mm to 200 mm, the length along the optical axis direction is 150 mm to 200 mm, the distance between the entrance end face of the hollow iron shell (31) and the accelerating electrode (2) is 30 mm to 45 mm, and the distance between the exit end face and the input port of the MCP detector (4) is 100 mm to 120 mm; the number of turns of the coil (32) is 100 to 400.

3. A strong radiation background light electronic signal extraction device according to claim 1 or 2, characterized in that: The potential difference between the accelerating electrode (2) and the photocathode (1) is 500V to 2000V.

4. The strong radiation background light electronic signal extraction device according to claim 3, characterized in that: The diameter of the photocathode (1) is 45 mm to 55 mm, and the dimension of the photocathode (1) along the length direction of the optical axis is 0.1 mm to 0.5 mm; The diameter of the accelerating electrode (2) is 45 mm to 55 mm, and the dimension along the optical axis direction is 0.1 mm to 0.5 mm; the distance between the accelerating electrode (2) and the photocathode (1) is 1 mm to 3 mm.

5. The strong radiation background light electronic signal extraction device according to claim 4, characterized in that: The current intensity of the focusing device (3) is 10A~250A.

6. The strong radiation background light electronic signal extraction device according to claim 5, characterized in that: The potential difference between the MCP detector (4) and the accelerating electrode (2) is 0V-1000V.

7. The strong radiation background light electronic signal extraction device according to claim 6, characterized in that: The MCP detector (4) has a diameter of 40 mm to 80 mm and a thickness of 0.2 mm to 0.5 mm.

8. A system for extracting electron signals from strong radiation background light, characterized in that: A strong radiation background photoelectron signal extraction device comprising any one of claims 1-7.

9. A method for extracting electron signals from strong radiation background light, based on a device for extracting electron signals from strong radiation background light according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: converting the received external optical radiation signal into a photoelectron signal through the photocathode (1), and outputting it to the accelerating electrode (2); Step 2: After the photoelectron signal is accelerated by the accelerating electrode (2), it is output to the entrance end face of the focusing device (3); Step 3, focusing the photoelectron signal by a focusing device (3), bending its running trajectory by 1 / 4 arc, and then outputting it to the MCP detector (4) through its exit end face; Step 4: The focused photoelectron signal is collected and multiplied by the MCP detector (4) to complete the extraction of the strong radiation background photoelectron signal.

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