6 Methods for determining the optimal thickness of LiF neutron conversion layers and methods for fabricating neutron conversion layers based on SiC / GaN nuclear radiation sensors

Abstract

This invention discloses 6 The method for determining the optimal thickness of the LiF neutron conversion layer and the method for fabricating the neutron conversion layer based on the SiC / GaN nuclear radiation sensor include the following steps: Step 1: Obtaining 6 The thickness of the LiF neutron conversion layer and 6 The curve relationship between LiF thermal neutron intrinsic detection efficiency and the highest thermal neutron intrinsic detection efficiency is defined in the curve relationship. 6 The thickness of the LiF neutron conversion layer is the initial optimal thickness; Step 2: Calculate and obtain the energy spectra of secondary α and T particles based on the initial optimal thickness obtained in Step 1, and determine whether to introduce an air layer; if yes, proceed to Step 3; if no, proceed to Step 4; Step 3: Introduce an air layer and calculate the discrimination thresholds for α and T to determine the optimal air layer thickness; Step 4: For 6 The initial optimal thickness of the LiF neutron conversion layer was verified. This invention... 6 The method for determining the optimal thickness of the LiF neutron conversion layer can obtain the optimal... 6 Parameters of the LiF neutron conversion layer were improved to enhance the fabrication efficiency of the neutron conversion layer in SiC / GaN nuclear radiation sensors.

Description

Technical Field

[0001] This invention belongs to the field of radiation detection technology, specifically relating to a... 6 Methods for determining the optimal thickness of the LiF neutron conversion layer and methods for fabricating the neutron conversion layer based on a SiC / GaN nuclear radiation sensor. Background Technology

[0002] In recent years, with the rapid development of nuclear technology applications, the demand for radiation detectors that can operate stably for extended periods in extremely complex environments (such as space environments and nuclear reactor cores with high radiation and complex temperatures) has become increasingly urgent. Semiconductor detectors possess advantages such as high energy resolution, high detection efficiency, small size, and fast response time, which are unmatched by other detectors. Their principle involves using semiconductor materials as the detection medium. Incident rays ionize within the semiconductor medium, forming electron-hole pairs. An external electric field causes these electron-hole pairs to drift, generating an output signal in the output circuit to complete the ray detection. However, traditional silicon and germanium semiconductor detectors can only be stored and operated at room temperature or low temperatures, and cannot function in harsh environments such as high temperatures and strong radiation fields.

[0003] SiC / GaN semiconductor materials are a new type of semiconductor material developed in the 21st century. Due to their unique characteristics such as large bandgap, high critical breakdown field strength, strong thermal stability, high electron mobility, high thermal conductivity, and excellent radiation resistance, they are a suitable replacement for traditional radiation detectors based on silicon, germanium, cadmium telluride, and cadmium zinc telluride. They are also considered a wide-bandgap semiconductor material with great potential for fabricating high-temperature, high-frequency, high-power, and radiation-resistant devices, achieving good detection results in alpha particles, X-rays, gamma rays, and neutrons. The surface of the semiconductor detector... 6 The thickness of the LiF coating has a significant impact on detection efficiency and energy resolution. Summary of the Invention

[0004] In view of this, in order to overcome the shortcomings of the prior art, the object of the present invention is to provide a 6 A method for determining the optimal thickness of the LiF neutron conversion layer and a method for fabricating the neutron conversion layer based on a SiC / GaN nuclear radiation sensor were developed, enabling the achievement of optimal thickness. 6 The parameters of the LiF neutron conversion layer are adjusted to improve the fabrication efficiency of the neutron conversion layer in SiC / GaN nuclear radiation sensors, thereby ultimately improving the sensor's detection efficiency.

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

[0006] One object of the present invention is to provide a method for fabricating a neutron conversion layer in a SiC / GaN nuclear radiation sensor, comprising the following steps:

[0007] Step 1: Obtain 6 The thickness of the LiF neutron conversion layer and 6 The curve relationship between LiF thermal neutron intrinsic detection efficiency and the highest thermal neutron intrinsic detection efficiency is defined in the curve relationship. 6 The thickness of the LiF neutron conversion layer is the initial optimal thickness;

[0008] Step 2: Calculate and obtain the secondary α and T particle energy spectrum based on the initial optimal thickness obtained in Step 1. Determine whether to introduce an air layer based on the secondary α and T particle energy spectrum. If yes, proceed to Step 3; otherwise, proceed to Step 4.

[0009] Step 3: Introduce an air layer and calculate the discrimination thresholds of α and T to determine the optimal air layer thickness;

[0010] Step 4: Based on the determinations made in Step 1 and / or Step 3 respectively 6 The initial and optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness were investigated under different neutron source term settings. 6 The relationship between the variation of LiF thermal neutron intrinsic detection efficiency and the actual efficiency of LiF thermal neutron detection. 6 The initial optimal thickness of the LiF neutron conversion layer was verified to confirm the... 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness, if the 6 If the initial optimal thickness of the LiF neutron conversion layer is not the optimal thickness, then repeat steps 1 to 4 until it is confirmed that the optimal thickness is achieved. 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness.

[0011] Specifically, since neutrons are uncharged, they do not ionize during their passage through semiconductors. Therefore, by selecting neutrons that readily react with certain nuclei to produce charged particles, and recording the ionization excitation caused by these charged particles, neutrons can be detected. This method is mainly used for slow neutron detection, and the most commonly used fixed-conversion-layer nuclides are... 6 Li nuclides, their nuclear reaction mechanisms are as follows:

[0012] n+ 6 Li→α+ 3 T+4.786MeV σ0=940±4b;

[0013] From the above formula, it can be seen that using... 6 Li exhibits a high reaction energy for neutron detection, making it easy to filter out the gamma background, and also has a high reaction cross-section, resulting in high neutron detection efficiency. Neutron detection is achieved by measuring... 6 The Li(n,T)α nuclear reaction is achieved through secondary α and T charged particles, with the energy deposited in the semiconductor on the order of MeV. However, secondary α particles are heavily charged particles, and in...6 During LiF transit, energy is depleted, preventing it from reaching the semiconductor. Therefore, an appropriate discrimination threshold is often set to statistically analyze secondary T charged particles.

[0014] Semiconductor detector surface 6 The thickness of the LiF coating affects the detection efficiency and energy resolution. 6 When LiF is thinner, the effect of self-absorption is smaller, resulting in higher energy resolution. This is beneficial for raising the lower limit of neutron energy spectrum measurements, but thinner... 6 LiF reduces detection efficiency; in high-energy neutron spectrum measurements, the low reaction cross-section and low statistical count are the main problems in this energy range. When using a thicker [reaction cross-section]... 6 A thicker LiF neutron conversion layer can improve detection efficiency, but this is not ideal. 6 LiF, however, sacrifices energy resolution. Therefore, we first obtain different... 6 LiF neutron conversion layer thickness and 6 The relationship between the intrinsic detection efficiency of LiF thermal neutrons can be found on its graph. 6 The maximum value of the LiF thermal neutron intrinsic detection efficiency corresponds to... 6 The optimal thickness of the LiF neutron conversion layer can be obtained. 6 The parameters of the LiF neutron conversion layer provide an important basis for subsequent processing and testing.

[0015] According to some preferred embodiments of the present invention, obtaining in step 1 6 The thickness of the LiF neutron conversion layer and 6 The method for plotting the relationship between the intrinsic detection efficiency of LiF thermal neutrons is as follows: simulation using Monte Carlo software is performed. 6 The thickness of the LiF neutron conversion layer and 6 The simulated piecewise linear plot of the LiF thermal neutron intrinsic detection efficiency was fitted to obtain the following result. 6 The thickness of the LiF neutron conversion layer and 6 The graph shows the relationship between the intrinsic detection efficiency of LiF thermal neutrons. In some preferred embodiments of the present invention, the Monte Carlo software includes MCNP6, Geant4, etc.

[0016] According to some preferred embodiments of the present invention, when performing simulation using a Monte Carlo software program, the input into the Monte Carlo software program is as follows: 6 The thickness range of the LiF neutron conversion layer is related to the load. 6 The thickness of the LiF neutron conversion layer substrate is on the same order of magnitude.

[0017] According to some preferred embodiments of the present invention, in step 2, when the energy spectrum of the secondary alpha particles partially overlaps with that of the secondary t particles, an air layer needs to be introduced. Since self-absorption causes the energy spectra of alpha particles and t particles to overlap, this is detrimental to neutron energy spectrum measurements. Therefore, the different energy decay coefficients of the secondary alpha and t particles in air can be considered... 6 An air layer is introduced between the LiF neutron conversion layer and the detector to separate the energy spectra of secondary alpha and T particles. According to SRIM software, the ranges of 2.73 MeV T particles and 2.06 MeV alpha particles in air are 67 mm and 12 mm, respectively. As the air layer thickness increases, the particles lose more energy, and the energy spectra of alpha and T particles are separated more effectively. Furthermore, T particles emitted at larger angles will not reach the semiconductor detector, and the low-energy tail of the T particle energy spectrum can be removed. This makes it easier to determine the discrimination thresholds for the secondary alpha and T particle energy spectra.

[0018] According to some preferred embodiments of the present invention, the method for determining the optimal air layer thickness in step 3 is as follows: using Monte Carlo software to simulate and obtain the energy spectra of secondary α particles and T particles under different air layer thicknesses, and obtaining the relationship between air layer thickness and... 6 After fitting the simulated line graph of LiF thermal neutron intrinsic detection efficiency, the air layer thickness and... 6 The curve relationship of LiF thermal neutron intrinsic detection efficiency; when the energy spectra of secondary alpha particles and T particles do not overlap and 6 The optimal air layer thickness corresponds to the highest intrinsic detection efficiency of LiF thermal neutrons.

[0019] According to some preferred embodiments of the invention, the thickness of the air layer ranges from 0 to 5 mm.

[0020] According to some preferred embodiments of the present invention, the method of step 4 is as follows: when it is determined in step 2 that an air layer needs to be introduced, based on the determinations made in steps 1 and 3 respectively... 6 The initial and optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness were investigated under different neutron source term settings. 6 The relationship between the variation of LiF thermal neutron intrinsic detection efficiency and the actual efficiency of LiF thermal neutron detection. 6 The initial optimal thickness of the LiF neutron conversion layer was verified.

[0021] According to some preferred embodiments of the present invention, the investigation of different neutron source term settings 6 The method for determining the variation of LiF thermal neutron intrinsic detection efficiency is as follows: [The method is to obtain...] 6 The thickness of the LiF neutron conversion layer and the α and T discrimination thresholds 6 The relationship between LiF thermal neutron intrinsic detection efficiency and the following graph:6 When the thickness of the LiF neutron conversion layer is the initial optimal thickness determined in step 1, 6 The relationship between LiF thermal neutron intrinsic detection efficiency and α and T discrimination thresholds.

[0022] According to some preferred embodiments of the invention, the different neutron source terms arrangement includes neutron incident directions parallel to the... 6 The neutron source of the LiF neutron conversion layer has a neutron incident direction perpendicular to the [structure / structure]. 6 LiF neutron conversion layer and the above 6 The LiF neutron conversion layer is an isotropic neutron source. Because 6 The LiF neutron conversion layer is a thin film structure; different neutron incident directions will affect... 6 The efficiency of LiF thermal neutron intrinsic detection is affected. In Monte Carlo software programs such as MCNP6, setting source terms with different neutron emission directions yields different results. 6 The LiF thermal neutron intrinsic detection efficiency results will provide important theoretical basis for the results of measurements under actual conditions.

[0023] According to some preferred embodiments of the invention, the load said 6 The substrate for the LiF neutron conversion layer is a SiC / GaN chip.

[0024] Another objective of this invention is to provide a method for fabricating a neutron conversion layer based on a SiC / GaN nuclear radiation sensor, wherein the neutron conversion layer is... 6 The preparation method of the LiF neutron conversion layer includes the following steps: according to the above... 6 The method for determining the optimal thickness of the LiF neutron conversion layer was obtained 6 The optimal thickness of the LiF neutron conversion layer. Specifically, when the optimal thickness of the LiF neutron conversion layer is determined... 6 After determining the optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness, electron beam evaporation vacuum deposition technology was used to prepare the film. 6 LiF coating. Compared with thermal evaporation technology, electron beam evaporation coating offers controllable beam ratio, heated substrate, and rotatable workpiece. Therefore, electron beam evaporation is superior to thermal evaporation coating. 6 LiF thin films are of higher quality; compared with magnetron sputtering deposition technology, electron beam evaporation deposition has a wider beam rate adjustment range. The high beam ratio makes it particularly suitable for thick plating. 6 LiF thin films can be deposited using electron beam evaporation, which can be done with powder or bulk materials, unlike magnetron sputtering which requires the preparation of sample targets of a specific diameter. Electron beam evaporation vacuum deposition technology enables the preparation of... 6 LiF coatings offer better stability and higher quality, effectively improving detector efficiency and energy resolution.

[0025] Furthermore, the electron gun filament is heated to 2500–3000°C by electricity, causing… 6 The LiF material is heated and melted, and then gradually evaporates onto the metal surface.

[0026] Furthermore, the film thickness was monitored in real time using an INFICON SQC-310 quartz crystal film thickness measuring instrument.

[0027] Furthermore, 6 The LiF coating equipment uses a four-source electron gun evaporation coating machine, which mainly consists of a vacuum chamber, a vacuum system, a composite vacuum gauge, a small electron beam evaporation source and electron gun power supply, a high-frequency switching electron gun high-voltage power supply, a temperature controller, a film thickness monitor, a water cooling system, a computer, and related software.

[0028] Due to the adoption of the above technical solutions, the advantages of this invention compared to existing technologies are: 6 Methods for determining the optimal thickness of the LiF neutron conversion layer and fabrication methods for the neutron conversion layer based on a SiC / GaN nuclear radiation sensor, by prior acquisition of... 6 The thickness of the LiF neutron conversion layer and 6 The relationship between the intrinsic detection efficiency of LiF thermal neutrons was calculated, yielding the energy spectra of secondary α and T particles, as well as the discrimination thresholds for α and T. This calculation fully considers the influencing factors of the sensor, allowing for the acquisition of optimal results. 6 The parameters of the LiF neutron conversion layer provide an important foundation for subsequent processing and testing, thereby improving the fabrication efficiency of the neutron conversion layer in SiC / GaN nuclear radiation sensors and ultimately enhancing the sensor's detection efficiency. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0030] Figure 1 This is a preferred embodiment of the present invention. 6 The thickness of the LiF neutron conversion layer and 6 A graph showing the relationship between the intrinsic detection efficiency of thermal neutrons in LiF;

[0031] Figure 2 This is a preferred embodiment of the present invention. 6 When the LiF neutron conversion layer thickness is 25 μm 6 The energy spectra of secondary α and T particles corresponding to the LiF neutron conversion layer;

[0032] Figure 3 This is a graph showing the relationship between the count and energy of secondary α and T particles when the air layer thickness is 3 mm according to a preferred embodiment of the present invention.

[0033] Figure 4 In a preferred embodiment of the present invention, the air layer thickness and 6 A graph showing the relationship between the intrinsic detection efficiency of thermal neutrons in LiF;

[0034] Figure 5 This is a preferred embodiment of the present invention. 6 The thickness of the LiF neutron conversion layer and the α and T discrimination thresholds 6 A graph showing the relationship between the intrinsic detection efficiency of thermal neutrons in LiF;

[0035] Figure 6 This is a preferred embodiment of the present invention. 6 When the LiF neutron conversion layer thickness is 25 μm 6 The relationship between LiF thermal neutron intrinsic detection efficiency and α and T discrimination thresholds;

[0036] Figure 7 This is the preferred embodiment of the invention, fabricated on a SiC / GaN chip. 6 Image of a LiF neutron conversion layer thin film. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention, 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 should fall within the scope of protection of the present invention.

[0038] One embodiment of this example 6 The method for determining the optimal thickness of the LiF neutron conversion layer includes the following steps:

[0039] Step 1: Obtain 6 The thickness of the LiF neutron conversion layer and 6 The curve relationship between LiF thermal neutron intrinsic detection efficiency and the highest thermal neutron intrinsic detection efficiency is defined in this curve relationship. 6 The thickness of the LiF neutron conversion layer is the initial optimal thickness.

[0040] Step 2: Calculate and obtain the secondary α and T particle energy spectra based on the initial optimal thickness obtained in Step 1. Determine whether to introduce an air layer based on the secondary α and T particle energy spectra. If the secondary α particle energy spectra and the secondary T particle energy spectra partially overlap, an air layer needs to be introduced, and then proceed to Step 3; otherwise, proceed to Step 4.

[0041] Step 3: Introduce an air layer and calculate the discrimination thresholds of α and T to determine the optimal air layer thickness.

[0042] The energy spectra of secondary alpha particles and T particles under different air layer thicknesses were obtained using Monte Carlo software simulation, and the relationship between air layer thickness and... 6 After fitting the simulated line graph of LiF thermal neutron intrinsic detection efficiency, the air layer thickness and... 6 The curve relationship of LiF thermal neutron intrinsic detection efficiency; when the energy spectra of secondary alpha particles and T particles do not overlap and 6 The optimal air layer thickness corresponds to the highest intrinsic detection efficiency of LiF thermal neutrons.

[0043] Step 4: Based on the determinations made in Step 1 and / or Step 3 respectively 6 The initial and optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness were investigated under different neutron source term settings. 6 The relationship between the LiF thermal neutron intrinsic detection efficiency and its variation includes: obtaining 6 The thickness of the LiF neutron conversion layer and the α and T discrimination thresholds 6 The relationship between LiF thermal neutron intrinsic detection efficiency and the following graph: 6 When the thickness of the LiF neutron conversion layer is the initial optimal thickness determined in step 1, 6 The graph showing the relationship between the intrinsic thermal neutron detection efficiency of LiF and the α and T discrimination thresholds is used to verify the accuracy of the initial optimal thickness determined in step 1. If the verification shows that the result is accurate, then it is confirmed. 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness, if 6 If the initial optimal thickness of the LiF neutron conversion layer is not the optimal thickness, then repeat steps 1 to 4 until confirmed. 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness.

[0044] Among them, different neutron source term settings include neutron incident directions parallel to 6 The neutron source of the LiF neutron conversion layer has neutron incident directions perpendicular to its direction. 6 LiF neutron conversion layer and related 6 The LiF neutron conversion layer is an isotropic neutron source.

[0045] Example 1: A method for fabricating a neutron conversion layer based on a SiC / GaN nuclear radiation sensor, comprising the following steps:

[0046] Step 1: Based on a 10mm×10mm×30mm (thickness) SiC / GaN chip, simulate using the MCNP6 Monte Carlo software program to obtain... 6 The thickness of the LiF neutron conversion layer and 6 A line graph showing the intrinsic detection efficiency of LiF thermal neutrons was used, and then a curve showing the relationship between the two was obtained by fitting the line graph. Figure 1 As shown. Among them, the input software program... 6 The thickness of the LiF neutron conversion layer ranges from 10 to 99 mm. The highest thermal neutron intrinsic detection efficiency is defined in the curve relationship graph. 6 The thickness of the LiF neutron conversion layer is the initial optimal thickness.

[0047] Depend on Figure 1 visible, 6 LiF thermal neutron intrinsic detection efficiency increases with... 6 The thickness of the LiF neutron conversion layer first increases and then decreases, reaching its maximum at a thickness of 25 μm. 6 The intrinsic detection efficiency of LiF thermal neutrons is 4.6%. Based on existing simulation results, formula (1) is obtained:

[0048] Re = 8E-05t 3 -0.0098t 2 +0.3606t+0.423 (1);

[0049] Where Re represents 6 LiF thermal neutron intrinsic detection efficiency, expressed as %; t represents... 6 The thickness of the LiF neutron conversion layer is expressed in μm.

[0050] Step 2: Calculate and obtain the secondary α and T particle energy spectrum based on the initial optimal thickness obtained in Step 1, and determine whether to introduce an air layer based on the secondary α and T particle energy spectrum.

[0051] when 6 The simulated energy spectra of secondary α and T particles when the initial optimal thickness of the LiF neutron conversion layer is 25 μm are as follows: Figure 2 As shown, it can be seen that at this time, due to the self-absorption process, the energy spectra of α and T are superimposed, and an air layer needs to be introduced.

[0052] Step 3: Introduce an air layer and use the MCNP6 Monte Carlo software program to simulate and obtain the energy spectra of secondary alpha particles and T particles under different air layer thicknesses, and obtain the relationship between air layer thickness and... 6After fitting the simulated piecewise linear plot of the LiF thermal neutron intrinsic detection efficiency, the relationship between air layer thickness and... 6 The curve relationship of LiF thermal neutron intrinsic detection efficiency (as shown in the figure) Figure 4 (As shown).

[0053] Within an air layer thickness range of 0–5 mm, multiple different point values ​​were substituted into the software program to simulate multiple α counts, T counts, and energy relationship graphs. From these graphs, the air layer thickness corresponding to the separation of the energy spectra of secondary α and T particles was identified. Then, based on… Figure 4 Find the corresponding thickness of these air layers 6 The intrinsic detection efficiency of LiF thermal neutrons ultimately revealed that, within the range of different air layer thicknesses corresponding to the ability to separate the energy spectra of secondary α and T particles, only when the air layer thickness is 3 mm does the corresponding efficiency... 6 The intrinsic detection efficiency of LiF thermal neutrons is the highest, therefore the optimal air layer thickness is determined to be 3 mm.

[0054] Specifically, for different air layer thicknesses, the air layer thickness and 6 The relationship between the intrinsic detection efficiency of LiF thermal neutrons is shown in the graph. Figure 4 As shown, Figure 4 Ralative efficiency in the absence of an air layer 6 Using the intrinsic detection efficiency of LiF thermal neutrons as a standard value, the simulation yields formula (2):

[0055] Re = e -0.42a (2);

[0056] In the formula, Re represents relative 6 LiF thermal neutron intrinsic detection efficiency; 'a' represents the thickness of the air layer, in mm.

[0057] Step 4: Based on the determinations made in Step 1 and / or Step 3 respectively 6 The initial and optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness were investigated under different neutron source term settings. 6 The relationship between the LiF thermal neutron intrinsic detection efficiency and its variation includes: obtaining 6 The thickness of the LiF neutron conversion layer and the α and T discrimination thresholds 6 The relationship between LiF thermal neutron intrinsic detection efficiency and the following graph: 6 When the thickness of the LiF neutron conversion layer is the initial optimal thickness determined in step 1, 6 The graph showing the relationship between the intrinsic thermal neutron detection efficiency of LiF and the α and T discrimination thresholds is used to verify the accuracy of the initial optimal thickness determined in step 1. If the verification shows that the result is accurate, then it is confirmed. 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness, if6 If the initial optimal thickness of the LiF neutron conversion layer is not the optimal thickness, then repeat steps 1 to 4 until confirmed. 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness.

[0058] Among them, different neutron source term settings include neutron incident directions parallel to 6 The neutron source of the LiF neutron conversion layer has neutron incident directions perpendicular to its direction. 6 LiF neutron conversion layer and related 6 The LiF neutron conversion layer is an isotropic neutron source.

[0059] Specifically, computational studies were conducted. 6 The influence of factors such as LiF neutron conversion layer thickness and discrimination threshold on intrinsic detection efficiency is calculated. 6 The Li concentration is 95%, and the density is 2.544 g / cm³. 3 , 6 The thickness of the LiF neutron conversion layer and the α and T discrimination thresholds 6 The relationship between the intrinsic detection efficiency of LiF thermal neutrons and the following is: Figure 5 As shown, from Figure 5 It can be seen that the verification shows that 5μm is 6 The conclusion regarding the optimal thickness of the LiF neutron conversion layer is correct.

[0060] Furthermore, when 6 The initial optimal thickness of the LiF neutron conversion layer was chosen to be 25 μm, under different discrimination thresholds. 6 The variation in LiF thermal neutron intrinsic detection efficiency is as follows: Figure 6 As shown, the simulation yields formula (3):

[0061] Re = -0.0012T + 4.4925 (3);

[0062] Where Re represents 6 LiF thermal neutron intrinsic detection efficiency, expressed as %; T represents the discrimination threshold, expressed as keV. Figure 6 It can be seen that, 6 The intrinsic detection efficiency of LiF thermal neutrons shows a linear relationship with the discrimination threshold, further verifying that 5μm is... 6 The conclusion regarding the optimal thickness of the LiF neutron conversion layer is correct.

[0063] 6 The fabrication of LiF thin films is crucial for enabling neutron sensors to detect neutrons, requiring... 6 The LiF thin film has controllable thickness, does not detach, and has no impact on detector performance after coating. 6 LiF materials 6The Li abundance was 95%. 6 When the LiF film is thin (≤1μm), secondary α and T particles can easily penetrate it, resulting in better energy resolution but lower neutron detection efficiency. 6 When the LiF film is relatively thick (≥10μm), 6 The LiF thin film itself exhibits significant absorption of α and T charged particles, resulting in high neutron detection efficiency but poor energy resolution. 6 For LiF films with a thickness ≥ 25 μm, the neutron detection efficiency decreases as the thickness increases.

[0064] Step 5: Fabricate a 25μm thick film on the SiC / GaN chip using electron beam evaporation vacuum deposition technology. 6 The LiF coating was prepared using a quad-source electron gun. The electron gun filament was heated to 2700℃, and the electron gun evaporation source had a power of 6 kW and a voltage of 8000 V. The film thickness was monitored in real time using an INFICON SQC-310 quartz crystal film thickness gauge. 6 LiF coating such as Figure 7 As shown, its intrinsic thermal neutron detection efficiency is 4.6%.

[0065] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A kind 6 The method for determining the optimal thickness of the LiF neutron conversion layer is characterized by, Includes the following steps: Step 1: Obtain 6 The thickness of the LiF neutron conversion layer and 6 The curve relationship between LiF thermal neutron intrinsic detection efficiency and the highest thermal neutron intrinsic detection efficiency is defined in the curve relationship. 6 The thickness of the LiF neutron conversion layer is the initial optimal thickness; Step 2: Calculate and obtain the secondary α and T particle energy spectrum based on the initial optimal thickness obtained in Step 1. Determine whether to introduce an air layer based on the secondary α and T particle energy spectrum. If yes, proceed to Step 3; otherwise, proceed to Step 4. Step 3: Introduce an air layer and calculate the discrimination thresholds of α and T to determine the optimal air layer thickness; Step 4: Based on the determinations made in Step 1 and Step 3 respectively 6 The initial and optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness were investigated under different neutron source term settings. 6 The relationship between the variation of LiF thermal neutron intrinsic detection efficiency and the actual efficiency of LiF thermal neutron detection. 6 The initial optimal thickness of the LiF neutron conversion layer was verified to confirm... 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness, if 6 If the initial optimal thickness of the LiF neutron conversion layer is not the optimal thickness, then repeat steps 1 to 4 until confirmed. 6 The initial optimal thickness of the LiF neutron conversion layer is the optimal thickness; In step 2, when the secondary alpha particle energy spectrum partially overlaps with the secondary t particle energy spectrum, an air layer needs to be introduced. In step 3, the method for determining the optimal air layer thickness is as follows: using Monte Carlo software to simulate and obtain the secondary alpha and t particle energy spectra under different air layer thicknesses, and obtaining the relationship between the air layer thickness and... 6 After fitting the simulated line graph of LiF thermal neutron intrinsic detection efficiency, the air layer thickness and... 6 The curve relationship of LiF thermal neutron intrinsic detection efficiency; when the energy spectra of secondary alpha particles and T particles do not overlap and 6 The optimal air layer thickness corresponds to the highest intrinsic detection efficiency of LiF thermal neutrons. The investigation under different neutron source term settings 6 The method for determining the variation of LiF thermal neutron intrinsic detection efficiency is as follows: [The method is to obtain...] 6 The thickness of the LiF neutron conversion layer and the α and T discrimination thresholds 6 The relationship between LiF thermal neutron intrinsic detection efficiency and the following graph: 6 When the thickness of the LiF neutron conversion layer is the initial optimal thickness determined in step 1, 6 The relationship between LiF thermal neutron intrinsic detection efficiency and α and T discrimination thresholds.

2. The determination method according to claim 1, characterized in that, In step 1, the acquisition 6 The thickness of the LiF neutron conversion layer and 6 The method for plotting the relationship between the intrinsic detection efficiency of LiF thermal neutrons is as follows: simulation using Monte Carlo software is performed. 6 The thickness of the LiF neutron conversion layer and 6 The simulated piecewise linear plot of the LiF thermal neutron intrinsic detection efficiency was fitted to obtain the following result. 6 The thickness of the LiF neutron conversion layer and 6 The curve relationship between the intrinsic detection efficiency of thermal neutrons in LiF.

3. The determination method according to claim 2, characterized in that, When performing a simulation using the Monte Carlo software program, the input into the Monte Carlo software program is as follows: 6 The thickness range of the LiF neutron conversion layer is related to the load. 6 The thickness of the LiF neutron conversion layer substrate is on the same order of magnitude.

4. The determination method according to claim 1, characterized in that, The thickness of the air layer ranges from 0 to 5 mm.

5. The determination method according to claim 1, characterized in that, The method for step 4 is as follows: when it is determined in step 2 that an air layer needs to be introduced, based on the determinations made in steps 1 and 3 respectively... 6 The initial and optimal thickness of the LiF neutron conversion layer and the optimal air layer thickness were investigated under different neutron source term settings. 6 The relationship between the variation of LiF thermal neutron intrinsic detection efficiency and the actual efficiency of LiF thermal neutron detection. 6 The initial optimal thickness of the LiF neutron conversion layer was verified.

6. The determination method according to claim 5, characterized in that, The different neutron source term settings include neutron incident directions parallel to the... 6 The neutron source of the LiF neutron conversion layer has a neutron incident direction perpendicular to the [structure / structure]. 6 LiF neutron conversion layer and the above 6 The LiF neutron conversion layer is an isotropic neutron source.

7. The determination method according to claim 1, characterized in that, The load described 6 The substrate for the LiF neutron conversion layer is a SiC / GaN chip.

8. A method for fabricating a neutron conversion layer based on a SiC / GaN nuclear radiation sensor, characterized in that, The neutron conversion layer is 6 The preparation method of the LiF neutron conversion layer includes the steps described in any one of claims 1-7. 6 The method for determining the optimal thickness of the LiF neutron conversion layer was obtained 6 The optimal thickness of the LiF neutron conversion layer.

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