A calibration method for thermal neutron time-of-flight spectrum

Abstract

An embodiment of the present application discloses a calibration method for a thermal neutron time-of-flight spectrum, including: obtaining a first electrical signal formed by a detector and a second electrical signal generated by a signal generator having a plurality of different first signal periods within a preset time range; according to the generation time of the signals, using the first electrical signal as the start signal and the second electrical signal as the end signal, converting the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value to obtain a corresponding time-pulse amplitude spectrum; based on each time-pulse amplitude spectrum and the corresponding first signal period, determining the target channel address corresponding to each first signal period; based on a plurality of different first signal periods, determining the correspondence between a plurality of different target channel addresses and the corresponding first signal periods, and obtaining the functional relationship between time and channel address by performing data fitting on the obtained multiple time and channel address data, thereby completing the calibration of the thermal neutron time-of-flight spectrum.

Description

Technical Field

[0001] This application relates to the technical field of thermal neutron measurement, and particularly to a calibration method for the flight time spectrum of thermal neutrons. Background Technique

[0002] In the process of establishing a thermal neutron reference radiation field, it is necessary to measure the energy spectrum of the thermal neutron reference radiation field by the time-of-flight method. When measuring the flight time spectrum, it is necessary to calibrate the flight time spectrum.

[0003] In the related art, due to the high energy and short flight time of fast neutrons, an electronics plug-in can be used for delay, so as to calibrate the flight time spectrum of fast neutrons; however, since the energy range of thermal neutrons is from 2.53 milli electron volts (meV) to 1 electron volt (eV), and the corresponding flight time of thermal neutrons is (0.108 - 2.15) milliseconds (ms), this flight time is too long for the electronics plug-in, and it is impossible to calibrate the flight time spectrum of thermal neutrons by the method of delaying with the electronics plug-in. It can be seen that there is an urgent need to provide a new method for calibrating the flight time spectrum of thermal neutrons. Summary of the Invention

[0004] The embodiment of this application provides a calibration method for the flight time spectrum of thermal neutrons.

[0005] The technical solution of this application is realized as follows:

[0006] This application provides a calibration method for the flight time spectrum of thermal neutrons, and the method includes:

[0007] Obtain a first electrical signal formed by a detector and a second electrical signal generated by a signal generator with multiple different first signal periods. Among them, the first electrical signal is a logic signal obtained after the detector signal generated by the detector passes through a preamplifier, a main amplifier, and a discriminator. The first signal period is within a preset time range, and the preset time range should match the flight time range of thermal neutrons;

[0008] According to the generation time of the signals, starting from the first electrical signal and ending with the second electrical signal, convert the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value to obtain a corresponding time pulse amplitude spectrum;

[0009] Based on each time pulse amplitude spectrum and the corresponding first signal period, determine the target channel address corresponding to each first signal period;

[0010] Based on the multiple different first signal periods, determine the correspondence between multiple different target channel addresses and the corresponding first signal periods. By performing data fitting on the obtained multiple time and channel address data, obtain the functional relationship between time and channel address, thereby completing the calibration of the thermal neutron flight time spectrum.

[0011] The calibration method of the thermal neutron flight time spectrum provided by the embodiments of the present application. Since the calibration of the neutron flight time spectrum is the calibration of the time-amplitude converter and the multi-channel analyzer used for neutron flight time measurement, therefore, a detector that does not require a neutron source excitation to generate an electrical signal can be used during calibration. For example, the U-235 fission ionization chamber used in this embodiment. Since the uranium target in the U-235 fission ionization chamber contains uranium isotopes U-234, U-235, U-236, and U-238 all having alpha radioactivity, the emitted alpha particles can be ionized in the working gas of the ionization chamber to generate an electrical signal, and it can be used as the start signal source of the time-amplitude converter, thus simplifying the experimental conditions. In addition, to solve the shortcoming of the short delay time of the electronics delay module, a signal generated by a signal generator is used as the stop signal of the time-amplitude converter. There is no time correlation between the signal formed by the detector and the signal generated by the signal generator, and the time difference between the two signals is random within the period of the signal generator. The formed pulse amplitude spectrum is an approximate rectangle. In the time pulse amplitude spectrum, the maximum value of the amplitude corresponds to the time period of the signal generator, so that the relationship between the time difference and the channel address can be established. By using multiple time periods that match the thermal neutron flight time, the corresponding relationships between multiple time differences and the corresponding channel addresses can be established. By performing data fitting on the obtained multiple time and channel address data, the functional relationship between time and channel address is obtained, thereby completing the calibration of the thermal neutron flight time spectrum. Thus, a first electrical signal formed by the detector and a second electrical signal generated by the signal generator having multiple different first signal periods are obtained. Among them, the first electrical signal is a logic signal obtained after the detector signal generated by the detector passes through a preamplifier, a main amplifier, and a discriminator. The first signal period is within a preset time range, and the preset time range should match the flight time range of thermal neutrons; according to the generation time of the signals, with the first electrical signal as the start signal and the second electrical signal as the end signal, the signal time difference between the first electrical signal and the second electrical signal is converted into a pulse amplitude value to obtain the corresponding time pulse amplitude spectrum; based on each time pulse amplitude spectrum and the corresponding first signal period, the target channel address corresponding to each first signal period is determined; based on multiple different first signal periods, the corresponding relationships between multiple different target channel addresses and the corresponding first signal periods are determined. By performing data fitting on the obtained multiple time and channel address data, the functional relationship between time and channel address is obtained, thereby completing the calibration of the thermal neutron flight time spectrum.That is to say, in this application, the detector signal generated by the detector is processed electronically to obtain a first electrical signal. Taking the first electrical signal as the start signal and the second electrical signal with multiple different first signal periods generated by the signal generator as the end signal, the signal time difference between the first electrical signal and the second electrical signal is converted into a pulse amplitude value to obtain the corresponding time-pulse amplitude spectrum. Based on each time-pulse amplitude spectrum and the corresponding first signal period, the target channel address corresponding to each first signal period is determined; based on multiple different first signal periods, the correspondence between multiple different target channel addresses and the corresponding first signal periods is determined, and by performing data fitting on the obtained multiple time and channel address data, the functional relationship between time and channel address is obtained, thereby completing the calibration of the flight time spectrum of thermal neutrons. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is an electronic block diagram for obtaining a pulse amplitude spectrum for calibrating the flight time spectrum of thermal neutrons provided by an embodiment of this application;

[0013] Figure 2 is a schematic flowchart of a method for calibrating the flight time spectrum of thermal neutrons provided by an embodiment of this application;

[0014] Figure 3 is a schematic diagram of the energy spectrum of thermal neutrons at 20 °C provided by an embodiment of this application;

[0015] Figure 4 is a schematic flowchart of another method for calibrating the flight time spectrum of thermal neutrons provided by an embodiment of this application;

[0016] Figure 5 is a schematic diagram of the time-pulse amplitude spectrum when the signal frequency of the signal generator provided by an embodiment of this application is 10 kHz;

[0017] Figure 6 is a schematic diagram of the time-pulse amplitude spectrum when the signal frequency of the signal generator provided by an embodiment of this application is 4 kHz;

[0018] Figure 7 is a schematic diagram of the time-pulse amplitude spectrum when the signal frequency of the signal generator provided by an embodiment of this application is 2 kHz;

[0019] Figure 8 is a schematic diagram of the time-pulse amplitude spectrum when the signal frequency of the signal generator provided by an embodiment of this application is 1 kHz;

[0020] Figure 9 is a schematic diagram of the time-pulse amplitude spectrum when the signal frequency of the signal generator provided by an embodiment of this application is 0.625 kHz;

[0021] Figure 10Schematic diagram of the functional relationship between time and address provided by the embodiments of the present application. Detailed implementation manners

[0022] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0023] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0024] Referring to "embodiments" herein means that specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0025] In order to better understand the calibration method of the thermal neutron flight time spectrum provided in the embodiments of the present application, first, the background technology of the calibration method of the time spectrum and the calibration method of the time spectrum in the related technology are described.

[0026] The thermal neutron reference radiation field is one of the standard reference radiation fields recommended by the International Organization for Standardization for determining the energy and fluence response of neutron measurement devices. According to ISO8529-1, Table 1 is the reference radiation field recommended by the International Organization for Standardization for determining the energy and fluence response of neutron measurement devices:

[0027]

[0028] Table 1

[0029] In the related art, due to the high energy and short flight time of fast neutrons, an electronics plug-in can be used for delay to calibrate the flight time spectrum of fast neutrons. However, since the energy range of thermal neutrons is 2.53 meV to 1 eV, the corresponding flight time of thermal neutrons is (0.108 to 2.15) ms, which is too long for an electronics plug-in. Using a delay broadening plug-in such as GG8020, in the factory default settings, the delay time length of a single module is (70 to 1000) nanoseconds (ns), and the delay broadening plug-in includes 8 modules, and the delay time length of the 8 modules is (0.56 to 8) μs. Even if the position of the jumper in the delay broadening plug-in is adjusted to further adjust the delay time length of a single module to (0.4 to 10) μs, the delay time length of the 8 modules is only (3.2 to 80) μs. It can be seen that after adjusting the position of the jumper in the delay broadening plug-in, the delay time of the electronics plug-in is still much smaller than the flight time of thermal neutrons. Therefore, in the process of establishing a thermal neutron reference radiation field, it is very difficult to use the signal delay function of the electronics plug-in to calibrate the flight time spectrum of thermal neutrons, and then obtain the neutron energy spectrum of the thermal neutron reference radiation field.

[0030] The following describes an exemplary application of the device for calibrating the flight time spectrum of thermal neutrons provided in the embodiments of the present application. Refer to Figure 1 as shown Figure 1 The figure shows an electronics block diagram for obtaining a pulse amplitude spectrum for calibrating the flight time spectrum of thermal neutrons. The electronics block diagram includes a detector 101, a signal generator 102, a preamplifier 103, a main amplifier 104, a discriminator 105, a time-to-amplitude converter (TAC) 106, a multi-channel analyzer (MCA) 107, and a data acquisition system 108. Among them, the detector 101 is used to form a detector signal, and the signal generator 102 is used to generate signals with multiple different signal periods; the preamplifier 103 is used to improve the signal-to-noise ratio of the signal and pre-amplify the signal; the main amplifier 104 is used to amplify the signal; the discriminator 105 is used to discriminate the signal amplitude and convert the signal above the discrimination threshold into a logic signal; the time-to-amplitude converter 106 is used to convert the time difference into a pulse signal proportional to the time difference; the multi-channel analyzer 107 is used to analyze the pulse amplitude value of the pulse signal, convert the pulse amplitude value into a corresponding channel address, and output it in the data acquisition system 108 to obtain a time pulse amplitude spectrum.

[0031] See Figure 2 , Figure 2 which is a schematic diagram of an implementation process of the method for calibrating the flight time spectrum of thermal neutrons provided in the embodiments of the present application. The method includes the following steps:

[0032] Step 201: Obtain a first electrical signal formed by a detector and a second electrical signal generated by a signal generator and having a plurality of different first signal periods.

[0033] The first electrical signal is a logic signal obtained after the detector signal generated by the detector passes through a preamplifier, a main amplifier, and a discriminator. The first signal period is within a preset time range, and the preset time range should match the flight time range of thermal neutrons.

[0034] In an embodiment of the present application, the detector is a device that can form a signal without the assistance of other radiation sources. The detector signal formed by the detector can be a pulsed electrical signal. The detector signal can be a pulsed electrical signal having a second signal period, or the detector signal can also not be a pulsed electrical signal having a second signal period. The second signal period can be the same as the first signal period, or the second signal period can also be different from the first signal period. In this regard, the present application does not make specific limitations.

[0035] In an embodiment of the present application, the first electrical signal is a logic signal obtained after the detector signal generated by the detector passes through a preamplifier, a main amplifier, and a discriminator. Here, the detector signal generated by the detector undergoes pre-amplification and signal-to-noise ratio improvement processing by the preamplifier, amplification and shaping processing by the main amplifier, and the detector signal above the electronic noise amplitude is converted into a logic signal by the discriminator, so as to use this logic signal as the first electrical signal.

[0036] In an embodiment of the present application, the second electrical signal is an electrical signal having a first signal period. It should be emphasized that since the flight time spectrum of thermal neutrons is calibrated, the preset time range should match the flight time range of thermal neutrons, and the selected first signal period must be within the preset time range. Here, since the signal generator can generate various periodic waveform signals, and the frequency range of the used signal generator is 1 hertz (Hz) to 120 megahertz (MHz), and the corresponding time period is 8.33 ns to 1 second (s), which can meet the requirement that the flight time range of thermal neutrons is (0.108 to 2.15) ms, the second electrical signal generated by the signal generator can be used as the stop signal of the time-to-amplitude converter. It should be noted that the number of the second electrical signals can be multiple.

[0037] It should be noted that when determining the flight time range of thermal neutrons, since there is a correlation between the flight time of thermal neutrons and the energy of thermal neutrons, it is assumed that the energy range of the thermal neutrons to be measured is 2.53 meV to 1 eV. According to the following formula 1, the corresponding flight time range of thermal neutrons can be determined to be (0.108 to 2.15) ms. Among them, in the non-relativistic approximation, the relationship between the flight time and energy of thermal neutrons can be expressed by formula 1:

[0038]

[0039] where, \(t\) represents the flight time of thermal neutrons, \(l\) represents the flight distance of thermal neutrons, and \(E\) n represents the energy of thermal neutrons, and \(m\) n represents the mass of thermal neutrons. Here, the mass of thermal neutrons is \(1.67\times10^{-27}\) kilograms (Kilogram, kg).

[0040] In one implementation scenario, the energy of thermal neutrons is the energy when neutrons reach thermal equilibrium with surrounding substances at room temperature. Referring to Figure 3 as shown, Figure 3 the energy spectrum of thermal neutrons at \(20^{\circ}C\) is shown. The horizontal axis data represents the neutron energy in millielectron volts (meV), and the vertical axis data represents the number of neutrons per square centimeter per millielectron volt, and the number of neutrons has been normalized. It can be seen from Figure 3 that the energy of thermal neutrons at room temperature is \(25.3\) meV.

[0041] In the embodiments of the present application, multiple different first signal periods include: \(T\) different first signal periods, where \(T\) is an integer greater than or equal to 2.

[0042] In the embodiments of the present application, since the flight time range of thermal neutrons is \((0.108 - 2.15)\) ms, and the selected preset time range should match the flight time range of thermal neutrons. The meaning of "match" is that the preset time range is slightly larger than the flight time range of thermal neutrons. Exemplarily, the \(T\) first signal periods selected within the preset time range can be \(0.1\) ms, \(0.25\) ms, \(0.5\) ms, \(1\) ms, and \(1.6\) ms. That is, each signal period such as \(0.1\) ms, \(0.25\) ms, \(0.5\) ms, \(1\) ms, and \(1.6\) ms corresponds to different flight times of thermal neutrons, and the signal frequencies of the signal generators corresponding to each first signal period, that is, different flight times of thermal neutrons, are \(10\) kilohertz (kilohertz, kHz), \(4\) kHz, \(2\) kHz, \(1\) kHz, and \(0.625\) kHz respectively.

[0043] In other embodiments of the present application, the detector contains uranium isotopes that can emit alpha particles, and the detector signal is the signal generated by the ionization of alpha particles emitted during the decay of uranium isotopes in the working gas.

[0044] In an embodiment of the present application, the detector is a device capable of emitting alpha particles. The detector can be a U-235 fission ionization chamber. Since the U-235 fission ionization chamber uses a enriched uranium target as the detection medium, it itself has alpha radioactivity. The uranium isotopes in the enriched uranium target of the U-235 fission ionization chamber include U-234, U-235, U-236, and U-238. When each uranium isotope decays, the alpha particles emitted ionize in the working gas. The ions and electrons generated by ionization move in an electric field, and induced charges are generated at the collection electrode, generating a detector signal. Thus, by using a detector containing uranium isotopes capable of emitting alpha particles, there is no need to introduce an additional radiation source to excite the signal, which simplifies the experimental conditions and at the same time ensures that the experimental personnel are not harmed by radiation exposure. Here, alpha decay is a type of radioactive decay, also known as nuclear decay. When alpha decay occurs, alpha particles are emitted from the alpha radiation source.

[0045] Step 202: According to the generation time of the signal, taking the first electrical signal as the start signal and the second electrical signal as the end signal, convert the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value to obtain a corresponding time-pulse amplitude spectrum.

[0046] In an embodiment of the present application, since there is no time correlation between the first electrical signal and the second electrical signal, the signal time difference (also known as the time interval) determined by taking the first electrical signal as the start signal and the second electrical signal as the end signal is random within the first signal period range.

[0047] In an embodiment of the present application, after obtaining the first electrical signal formed by the detector and the second electrical signal with the first signal period generated by the signal generator, the first electrical signal and the second electrical signal are input into a time-to-amplitude converter. The time-to-amplitude converter, according to the generation time of the signal, takes the first electrical signal as the start signal and the second electrical signal as the end signal, and converts the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value to obtain a corresponding time-pulse amplitude spectrum.

[0048] Step 203: Based on each time-pulse amplitude spectrum and the corresponding first signal period, determine the target channel address corresponding to each first signal period.

[0049] In an embodiment of the present application, after converting the signal time difference between the first electrical signal and the second electrical signal into a pulse signal proportional to the signal time difference according to the generation time of the signal, taking the first electrical signal as the start signal and the second electrical signal as the end signal, the pulse signal is input into a multi-channel analyzer. The multi-channel analyzer analyzes the pulse amplitude value of the pulse signal to obtain a corresponding time-pulse amplitude spectrum. The maximum amplitude value of each time-pulse amplitude spectrum corresponds to the corresponding first signal period.

[0050] Step 204: Based on multiple different first signal periods, determine the correspondence between multiple different target channel addresses and the corresponding first signal periods. By performing data fitting on the obtained multiple time and channel address data, obtain the functional relationship between time and channel address, thereby completing the calibration of the thermal neutron time-of-flight spectrum.

[0051] In the embodiments of the present application, the functional relationship between time and channel address refers to a one-to-one corresponding functional relationship between time and channel address.

[0052] In the embodiments of the present application, after determining the target channel address corresponding to each first signal period in each time pulse amplitude spectrum and the corresponding first signal period, based on multiple different first signal periods, determine the correspondence between each target channel address among the multiple different target channel addresses and the corresponding first signal period. By performing data fitting on the obtained multiple time and channel address data, obtain the functional relationship between time and channel address, thereby completing the calibration of the thermal neutron time-of-flight spectrum.

[0053] The method for calibrating the thermal neutron time-of-flight spectrum provided by the embodiments of the present application obtains the first electrical signal formed by the detector and the second electrical signal with multiple different first signal periods generated by the signal generator. Among them, the first electrical signal is the logic signal obtained after the detector signal generated by the detector passes through the preamplifier, main amplifier, and discriminator. The first signal period is within a preset time range, and the preset time range is slightly larger than the time-of-flight range of thermal neutrons; according to the generation time of the signals, using the first electrical signal as the start signal and the second electrical signal as the end signal, convert the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value to obtain the corresponding time pulse amplitude spectrum; based on each time pulse amplitude spectrum and the corresponding first signal period, determine the target channel address corresponding to each first signal period; based on multiple different first signal periods, determine the correspondence between multiple different target channel addresses and the corresponding first signal periods. By performing data fitting on the obtained multiple time and channel address data, obtain the functional relationship between time and channel address, thereby completing the calibration of the thermal neutron time-of-flight spectrum; that is to say, the present application uses the detector signal generated by the detector to obtain the first electrical signal after electronic processing, and uses the first electrical signal as the start signal and the second electrical signal with multiple different first signal periods generated by the signal generator as the end signal, convert the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value to obtain the corresponding time pulse amplitude spectrum; based on each time pulse amplitude spectrum and the corresponding first signal period, determine the target channel address corresponding to each first signal period; based on multiple different first signal periods, determine the correspondence between multiple different target channel addresses and the corresponding first signal periods. By performing data fitting on the obtained multiple time and channel address data, obtain the functional relationship between time and channel address, thereby completing the calibration of the thermal neutron time-of-flight spectrum.

[0054] See Figure 4 , Figure 4 which is a schematic diagram of an implementation process of a method for calibrating the time-of-flight spectrum of thermal neutrons provided by an embodiment of the present application. The method includes the following steps:

[0055] Step 301: Obtain a first electrical signal formed by a detector and a second electrical signal generated by a signal generator with multiple different first signal periods.

[0056] The first electrical signal is a logic signal obtained after the detector signal generated by the detector passes through a preamplifier, a main amplifier, and a discriminator. The first signal period is within a preset time range, and the preset time range should match the time-of-flight range of thermal neutrons.

[0057] The multiple different first signal periods include: T first signal periods, where T is an integer greater than or equal to 2.

[0058] Step 302: When the signal period of the signal generator is each first signal period, according to the generation time, with the first electrical signal as the start signal and the second electrical signal as the end signal, convert the multiple signal time differences between the first electrical signal and the second electrical signal into pulse amplitude values of pulse signals proportional to the signal time differences to obtain corresponding time-pulse amplitude spectra.

[0059] In an embodiment of the present application, the horizontal axis data in the time-pulse amplitude spectrum is the channel address, and the vertical axis data is the count.

[0060] In an embodiment of the present application, the channel address is a digital quantity representing the pulse amplitude value. It can be understood that the channel address is a value of one of the equal divisions (such as being equally divided into 1024 channels, 2048 channels, etc.) for a preset pulse amplitude value, that is, there is a one-to-one correspondence between the channel address and the amplitude value. The count represents the number of times each amplitude value appears in the pulse signal.

[0061] In an embodiment of the present application, when the signal period of the signal generator is each first signal period, for the time-to-amplitude converter, according to the generation time of the signal, with the first electrical signal as the start signal and the second electrical signal as the end signal, input the pulse signal proportional to the signal time difference between the first electrical signal and the second electrical signal into a multi-channel analyzer. The multi-channel analyzer analyzes the amplitude value of the pulse signal and inputs the obtained signal into a data acquisition system to obtain a time-pulse amplitude spectrum.

[0062] Step 303: From each time-pulse amplitude spectrum corresponding to each first signal period, determine that the channel address corresponding to the pulse amplitude peak is the target channel address corresponding to each first signal period.

[0063] In the embodiments of the present application, the peak pulse amplitude is the maximum amplitude value in the time pulse amplitude spectrum corresponding to each first signal period, and the peak pulse amplitude represents the target channel address, corresponding to the first signal period currently used by the signal generator.

[0064] In the embodiments of the present application, for T time pulse amplitude spectra, the channel address corresponding to the peak pulse amplitude is determined as the target channel address corresponding to each first signal period from the time pulse amplitude spectra corresponding to each first signal period. Here, since there is no time correlation between the first electrical signal formed by the detector and the second electrical signal generated by the signal generator, the time difference formed between the first electrical signal and the second electrical signal shows a random distribution from 0 to the first signal period used by the signal generator, and the time pulse amplitude spectrum presented on the time-of-flight spectrum is rectangular, where the maximum pulse amplitude value in the time pulse amplitude spectrum corresponds to the first signal period used by the signal generator; pulse signals with different pulse amplitude values appear at different channel addresses, and the larger the pulse amplitude value of the pulse signal, the larger the corresponding channel address.

[0065] In a realizable application scenario, taking the selected T first signal periods as 0.1 ms, 0.25 ms, 0.5 ms, 1 ms, and 1.6 ms as examples, and the signal frequencies of the signal generator corresponding to each first signal period are 10 kHz, 4 kHz, 2 kHz, 1 kHz, and 0.625 kHz respectively, the measured time pulse amplitude spectra are as Figures 5 to 9 shown, Figure 5 shows the time pulse amplitude spectrum when the signal frequency of the signal generator is 10 kHz, Figure 6 shows the time pulse amplitude spectrum when the signal frequency of the signal generator is 4 kHz, Figure 7 shows the time pulse amplitude spectrum when the signal frequency of the signal generator is 2 kHz, Figure 8 shows the time pulse amplitude spectrum when the signal frequency of the signal generator is 1 kHz, Figure 9 shows the time pulse amplitude spectrum when the signal frequency of the signal generator is 0.625 kHz. It can be seen from Figures 5 to 9 that when the signal frequencies of the signal generator are 10 kHz, 4 kHz, 2 kHz, 1 kHz, and 0.625 kHz, the corresponding target channel addresses are 51, 128, 255, 510, and 817 respectively. The relationship between the first signal period (also known as time) and the target channel address can be represented by Table 2:

[0066] First signal period / ms 0.1 0.25 0.5 1 1.6 Target track address 51 128 255 510 817

[0067] Table 2

[0068] Step 304: Perform data fitting on multiple first signal periods and multiple target channel addresses to obtain the functional relationship between time and channel address, thereby completing the calibration of the time-of-flight spectrum of thermal neutrons.

[0069] In the embodiment of the present application, the functional relationship between time and channel address is obtained through data fitting.

[0070] In the embodiment of the present application, when performing data fitting on T first signal periods and T target channel addresses, the Python computer language can be used to fit the T first signal periods and T target channel addresses with a linear function.

[0071] In the embodiment of the present application, after determining the target channel address corresponding to each first signal period based on the pulse amplitude spectrum and each first signal period, perform data fitting on T first signal periods and T target channel addresses to obtain the functional relationship between time and channel address, thereby completing the calibration of the time-of-flight spectrum of thermal neutrons. Here, after determining the functional relationship between time and channel address, the neutron energy spectrum of thermal neutrons is obtained according to the time-of-flight spectrum of thermal neutrons, thereby laying a foundation for accurately measuring the thermal neutron fluence rate.

[0072] In an implementable application scenario, combining the measurement data (0.1, 51), (0.25, 128), (0.5, 255), (1, 510), and (1.6, 817) in Table 2 where there is a corresponding relationship between the first signal period and the target channel address, perform data fitting on these data to obtain the functional relationship between time and channel address, that is, the fitting straight line is as Figure 10 shown. Here, the functional relationship between time and channel address can be expressed by Formula 2:

[0073] Time = 1.95901729E-3 × Channel Address + 3.41105253 (Formula 2)

[0074] In this way, by establishing the functional relationship between time and channel address, calibrate the time-to-amplitude converter and the multi-channel analyzer, and then complete the calibration of the time-of-flight spectrum of thermal neutrons. Further, the neutron energy spectrum of thermal neutrons is obtained according to the time-of-flight spectrum of thermal neutrons, thereby laying a foundation for accurately measuring the thermal neutron fluence rate.

[0075] It should be noted that the descriptions of the same steps and the same content in this embodiment and other embodiments can be referred to the descriptions in other embodiments, and will not be repeated here.

[0076] In several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the displayed or discussed components can be through some interfaces. The indirect coupling or communication connection of devices or units can be electrical, mechanical, or other forms.

[0077] The units described above as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0078] In addition, in each embodiment of this application, each functional unit can be fully integrated in a processing module, or each unit can be separately used as a unit, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware, or in the form of hardware plus software functional units.

[0079] In the method embodiments disclosed in several method embodiments provided in this application, they can be arbitrarily combined without conflict to obtain new method embodiments. The features disclosed in several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments. The features disclosed in several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0080] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A method for calibrating thermal neutron time-of-flight spectrum, characterized in that: The method comprises: Obtaining a first electrical signal generated by a detector and a second electrical signal generated by a signal generator having a plurality of different first signal periods, wherein the first electrical signal is a logic signal obtained by passing the detector signal generated by the detector through a preamplifier, a main amplifier, and a discriminator, the first signal period is within a preset time range, and the preset time range must match the flight time range of thermal neutrons, the detector is a U-235 fission ionization chamber containing a uranium isotope capable of emitting alpha particles, and the detector signal is a signal generated by ionization of alpha particles emitted during decay of the uranium isotope in a working gas; According to the generation time of the signals, with the first electrical signal as the start signal and the second electrical signal as the end signal, the signal time difference between the first electrical signal and the second electrical signal is converted into a pulse amplitude value to obtain a corresponding time pulse amplitude spectrum; Determining a target track address corresponding to each first signal period based on each time pulse amplitude spectrum and the corresponding first signal period; Based on the multiple different first signal periods, the corresponding relationship between multiple different target track addresses and corresponding first signal periods is determined, and by performing data fitting on the multiple time and track address data obtained, the functional relationship between time and track address is obtained, thereby completing the calibration of the thermal neutron flight time spectrum.

2. The method according to claim 1, characterized in that The method converts the signal time difference between the first electrical signal and the second electrical signal into a pulse amplitude value according to the generation time of the signal, taking the first electrical signal as the start signal and the second electrical signal as the end signal, to obtain a corresponding time pulse amplitude spectrum, including: When the signal period of the signal generator is each first signal period, according to the generation time, with the first electrical signal as the start signal and the second electrical signal as the end signal, the multiple signal time differences between the first electrical signal and the second electrical signal are converted into pulse amplitude values of pulse signals proportional to the signal time differences to obtain a corresponding time pulse amplitude spectrum.

3. The method according to claim 1, characterized in that The step of determining the target track address corresponding to each first signal period based on each time pulse amplitude spectrum and the corresponding first signal period includes: From the time pulse amplitude spectrum corresponding to each first signal period, a track address corresponding to a pulse amplitude peak is determined as the target track address corresponding to each first signal period.

4. The method according to claim 1, wherein The determining, based on the multiple different first signal periods, the corresponding relationship between the multiple different target addresses and the corresponding first signal periods includes: Data fitting is performed on the multiple first signal periods and the multiple target track addresses to obtain the functional relationship between time and track address.

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