Novel cathode structure design for fission ionization chambers, and particle identification methods, systems, equipment, and media.

Abstract

This invention discloses a novel cathode structure design and particle identification method, system, equipment, and medium for a fission ionization chamber, belonging to the field of nuclear radiation detection technology. It includes: designing a special cathode structure constrained by the range difference between alpha particles and low-energy fission fragments in the working gas, resulting in a differential induced length and a non-uniform weighted potential cathode; performing position-weighted accumulation of the induced charge distribution along the drift direction of the incident particle ionization trajectory, and obtaining the amplitude of the induced signal for each electrode through the calculated summation; alpha particles and low-energy fission fragments forming spatially separated clusters in the two-dimensional discrimination space, and classifying the incident particle type based on cluster affiliation. This invention constructs an ionization distribution coefficient using the ratio of the cathode induced signal amplitude to the anode induced signal amplitude, quantifying the difference in the spatial distribution of the ionization trajectories of the two types of particles into an independent parameter, which, together with the anode induced signal amplitude, constructs the two-dimensional discrimination space.

Description

Technical Field

[0001] This invention relates to the field of nuclear radiation detection technology, specifically to a novel cathode structure design for a fission ionization chamber and a particle identification method, system, equipment, and medium. Background Technology

[0002] Fission cross-section is a key physical quantity in nuclear reactions. Among existing fission cross-section measurement techniques, fission ionization chambers are widely used due to their simple structure and high stability. However, when differentiating between alpha particles and low-energy fission fragments, existing fission ionization chambers typically only measure the deposition energy of particles in the gas using anodic signals and classify particles solely based on energy thresholds, without employing cathode signals for further differentiation.

[0003] Existing fission ionization chambers employ a flat-plate cathode, with a linearly distributed weighted potential within the cathode induction region, constituting a uniform cathode induction structure. Although alpha particles and low-energy fission fragments exhibit significant differences in range within the working gas, and their ionization trajectories possess distinctly different spatial distribution characteristics, the uniform cathode induction structure cannot effectively distinguish between these differences in ionization distribution.

[0004] Therefore, when the amplitudes of the anodic induction signals of alpha particles and low-energy fission fragments are similar, the uniform cathode induction structure has no difference in its induction response to the ionization trajectories of the two types of particles. As a result, the two particles overlap significantly in the signal space, making it impossible to effectively distinguish the particle type by simply relying on the amplitude of the anodic signal, thus causing misjudgment. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention provides a novel cathode structure design for a fission ionization chamber and a method, system, device and medium for particle identification.

[0006] Therefore, the technical problem solved by the present invention is that the existing fission ionization chamber adopts a uniform cathode induction structure, which cannot effectively distinguish the spatial distribution differences of ionization trajectories of alpha particles and low-energy fission fragments in the working gas, resulting in the overlap of the two types of particles in the signal space, and the particle identification accuracy relying solely on the amplitude of the anode signal is low.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a novel cathode structure design and particle identification method for a fission ionization chamber, comprising the following steps: A specially designed cathode structure is constructed based on the range difference between alpha particles and low-energy fission fragments in the working gas; a non-uniform induction construction is performed on the cathode induction region to obtain a differential induction length and a non-uniform weighted potential cathode; in the weighted potential field established by the non-uniform weighted potential cathode, the induced charge distribution of the incident particle ionization trajectory in the drift direction is accumulated by position weighting, and the amplitude of the induced signal of each electrode is obtained by the calculated summation result; an ionization distribution coefficient is constructed based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude in the amplitude of each electrode induced signal; a two-dimensional discrimination space is constructed based on the anode induced signal amplitude and the ionization distribution coefficient, and alpha particles and low-energy fission fragments form spatially separated clustering regions in the two-dimensional discrimination space; the incident particle type is classified according to the clustering affiliation.

[0008] As a preferred embodiment of the novel cathode structure design and particle identification method for a fission ionization chamber described in this invention, the step of constructing the non-uniform induction cathode includes:

[0009] The traditional cathode structure is cut into electrodes, resulting in a novel cathode and a protective ring structure.

[0010] The cathode sensing region is divided into a sensitive sensing region and a semi-sensitive sensing region along the drift direction;

[0011] The sensitive response region covers the spatial range of the end of the low-energy fission fragment range, and the semi-sensitive response region covers the spatial range of the alpha particle range. The differential sensing length is determined based on the spatial boundary between the sensitive response region and the semi-sensitive response region. The differential sensing length can be adjusted by the size of the novel cathode to obtain the differential sensing length and the non-uniform weighted potential cathode.

[0012] As a preferred embodiment of the novel cathode structure design and particle identification method for a fission ionization chamber described in this invention, the step of performing the position-weighted accumulation includes: based on the weighted potential distribution of the non-uniform weighted potential cathode in the drift direction, multiplying the induced charge generated at each position on the ionization trajectory of the incident particle with the corresponding weighted potential value one by one and summing the results to obtain a summation result; using the time integral of the summation result with the carrier transit process as the induced signal waveform of each electrode; and extracting the induced signal waveform to obtain the induced signal amplitude of each electrode.

[0013] As a preferred embodiment of the novel cathode structure design and particle identification method for a fission ionization chamber described in this invention, the step of extracting the induced signal waveform includes: setting a trigger threshold for the induced signal waveform, searching for a maximum value point within a time interval where the waveform amplitude exceeds the trigger threshold; recording the waveform amplitude value at the time corresponding to the maximum value point, and using the amplitude value as the induced signal amplitude of the corresponding electrode to obtain the induced signal amplitude of each electrode.

[0014] As a preferred embodiment of the novel cathode structure design and particle identification method for a fission ionization chamber described in this invention, the step of constructing the ionization distribution coefficient includes: acquiring several sampling points of the induced signal waveform of each electrode, and calculating the average amplitude of the sampling points; using the average amplitude as the baseline bias value of the corresponding electrode, subtracting the baseline bias value of the corresponding electrode from the amplitude of the induced signal of each electrode to obtain the baseline-corrected amplitude of the induced signal of each electrode; comparing the baseline-corrected amplitude of the anode induced signal with a preset effective event energy threshold; if the baseline-corrected amplitude of the anode induced signal is lower than the effective event energy threshold, then marking the current event as an invalid event and discarding it; if the baseline-corrected amplitude of the anode induced signal is not lower than the effective event energy threshold, then dividing the baseline-corrected amplitude of the cathode induced signal by the baseline-corrected amplitude of the anode induced signal to obtain the ionization distribution coefficient of the current particle event.

[0015] As a preferred embodiment of the novel cathode structure design and particle identification method for a fission ionization chamber described in this invention, the step of classifying the incident particle type based on clustering includes: collecting a set of known α-particle standard source event points and a set of known fission fragment event points; calculating the mean vector and covariance matrix of each of the α-particle event point set and the fission fragment event point set in a two-dimensional discrimination space to obtain their respective two-dimensional Gaussian distribution parameters; using the curve formed by the intersection of the equiprobability density lines of the α-particle two-dimensional Gaussian distribution parameters and the low-energy fission fragment two-dimensional Gaussian distribution parameters as the initial discrimination boundary, calculating the α-particle event point set... The total misclassification rate of the low-energy fission fragment event set under the initial discrimination boundary is calculated; the initial discrimination boundary is iteratively corrected until the total misclassification rate converges to the minimum value, and the converged discrimination boundary is solidified as the classification boundary of the two-dimensional discrimination space; in the two-dimensional discrimination space, the coordinate position formed by the amplitude of the anodic induction signal and the ionization distribution coefficient corresponding to the test particle event is determined, and the relative relationship between the coordinate position and the classification boundary is determined. Test particles whose coordinate positions fall on one side of the α particle clustering region of the classification boundary are determined as α particles, and test particles whose coordinate positions fall on one side of the low-energy fission fragment clustering region of the classification boundary are determined as low-energy fission fragments.

[0016] This invention provides a novel cathode structure design for a fission ionization chamber and a particle identification system.

[0017] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a novel cathode structure design and particle identification system for a fission ionization chamber, comprising: a fission ionization chamber, a signal acquisition unit, a processing unit, and a classification and identification unit;

[0018] The fission ionization chamber is equipped with an anode and a non-uniform weighted potential cathode. The sensing region of the non-uniform weighted potential cathode is constructed non-uniformly based on the range difference of alpha particles and low-energy fission fragments in the working gas of the ionization chamber, forming a sensitive region and a semi-sensitive region with different sensing lengths, so as to form a weighted potential field in the sensitive region of the ionization chamber.

[0019] The signal acquisition unit is used to synchronously acquire the anode induction signal output by the anode and the cathode induction signal output by the non-uniform weighted potential cathode.

[0020] The processing unit is used to perform position-weighted accumulation of the induced charge distribution of the incident particle ionization trajectory along the charge drift direction to obtain the amplitude of the cathode induced signal and the amplitude of the anode induced signal; and to calculate the ionization distribution coefficient based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude.

[0021] The classification and identification unit is used to construct a two-dimensional discrimination space composed of the amplitude of the anode induction signal and the ionization distribution coefficient; and to determine the type of incident particles based on the clustering regions in the two-dimensional discrimination space where alpha particles and low-energy fission fragments are separated from each other.

[0022] The present invention provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the novel cathode structure design and particle identification method for a fission ionization chamber.

[0023] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of a novel cathode structure design and particle identification method for a fission ionization chamber.

[0024] The beneficial effects of this invention are as follows: By constraining the range difference between alpha particles and low-energy fission fragments in the working gas, the cathode structure is specially designed to non-uniformly construct the cathode weighted potential. This results in a very low cathode weighted potential, close to 0, in regions far from the cathode; while in a small region around the cathode, the weighted potential rapidly increases to 1. Thus, the cathode sensing region is divided into a sensitive response region and a semi-sensitive response region, enabling the non-uniform weighted potential cathode to produce different sensing responses to the spatial distribution differences in the ionization trajectories of the two types of particles. Based on this, this invention constructs an ionization distribution coefficient using the ratio of the cathode sensing signal amplitude to the anode sensing signal amplitude, quantifying the difference in the spatial distribution of the ionization trajectories of the two types of particles into an independent parameter, which, together with the anode sensing signal amplitude, constructs a two-dimensional discrimination space.

[0025] Since alpha particles and low-energy fission fragments form spatially separated clusters in the two-dimensional discrimination space, even if the amplitudes of their anode induction signals are similar, the difference in their ionization distribution coefficients can still effectively separate the two types of particles in the two-dimensional discrimination space. This solves the problem of overlapping signals of the two types of particles and inaccurate identification under the existing uniform cathode induction structure. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of 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.

[0027] Figure 1 The above is a flowchart illustrating a novel cathode structure design for a fission ionization chamber and a particle identification method, as provided in one embodiment of the present invention.

[0028] Figure 2 The flowchart illustrates the waveform amplitude extraction of a novel cathode structure design for a fission ionization chamber and a particle identification method, as provided in one embodiment of the present invention.

[0029] Figure 3 A comparison of an existing cathode structure diagram (left) and a novel cathode structure design diagram (right) for a fission ionization chamber according to an embodiment of the present invention.

[0030] Figure 4 A comparison of the weighted potential distribution of an existing cathode (left figure) and the weighted potential distribution of a novel cathode structure (right figure) for a fission ionization chamber according to an embodiment of the present invention. Detailed Implementation

[0031] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. 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 protection scope of the present invention.

[0032] Example 1, referring to Figures 1-4 This is one embodiment of the present invention, which provides a novel cathode structure design for a fission ionization chamber and a particle identification method, including the following steps:

[0033] Constrained by the range difference between alpha particles and low-energy fission fragments in the working gas, the traditional cathode is cut into a novel cathode and guard ring structure. The cathode induction region is non-uniformly constructed to obtain a cathode with differential induction length and non-uniform weighted potential. A typical novel cathode structure design and weighted potential distribution are shown in the figure. Figure 3 , Figure 4 As shown, the fission target is located at the center of the novel cathode;

[0034] In the weighted potential field established by the non-uniform weighted potential cathode, the induced charge distribution of the incident particle ionization trajectory in the drift direction is accumulated by position weighting, and the amplitude of the induced signal of each electrode is obtained by the summation result.

[0035] An ionization distribution coefficient is constructed based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude in the amplitude of each electrode induced signal.

[0036] A two-dimensional discrimination space is constructed using the amplitude of the anode induction signal and the ionization distribution coefficient. Alpha particles and low-energy fission fragments form spatially separated clusters in the two-dimensional discrimination space, and the incident particle types are classified according to their cluster affiliation.

[0037] Existing fission ionization chambers employ a uniform cathode induction structure, which cannot effectively distinguish the spatial distribution differences of ionization trajectories of alpha particles and low-energy fission fragments in the working gas. This results in overlap of the two types of particles in the signal space, leading to low particle identification accuracy.

[0038] Constrained by the range difference between alpha particles and low-energy fission fragments in the working gas, the cathode structure is specially designed to non-uniformly construct the cathode weighted potential. This results in a very low weighted potential, close to 0, in regions far from the cathode, while rapidly increasing to 1 in a small area around the cathode. Consequently, the cathode sensing region is divided into a highly sensitive region (weighted potential greater than 0.5) and a semi-sensitive region (weighted potential less than 0.5), allowing the non-uniformly weighted potential cathode to produce different sensing responses to the spatial distribution differences in the ionization trajectories of the two types of particles. Based on this, the invention constructs an ionization distribution coefficient using the ratio of the cathode sensing signal amplitude to the anode sensing signal amplitude, quantifying the difference in the spatial distribution of the ionization trajectories of the two types of particles into an independent parameter, which, together with the anode sensing signal amplitude, constructs a two-dimensional discrimination space.

[0039] Example 2, refer to Figures 1-4 As an embodiment of the present invention, based on the previous embodiment, a novel cathode structure design for a fission ionization chamber and a particle identification method are provided, including the following steps:

[0040] S1. Using the range difference between alpha particles and low-energy fission fragments in the working gas as a constraint, non-uniform induction is constructed in the cathode induction region to obtain the differential induction length and non-uniform weighted potential cathode.

[0041] In this embodiment, the working gas of the fission ionization chamber is a mixture of argon and methane (volume ratio 90:10) at a pressure of 0.1 MPa. Experimental calibration shows that the range of 5 MeV alpha particles in the working gas is approximately 34 mm, and the range of 5 MeV fission fragments in the working gas is approximately 3 mm. The total length of the cathode sensitive sensing region is set to 15 mm, completely covering the maximum range of low-energy fission fragments, but less than the range of alpha particles.

[0042] The steps for constructing the non-uniform induction are as follows:

[0043] The traditional cathode structure is cut into electrodes, resulting in a novel cathode and a protective ring structure.

[0044] The cathode sensing region is divided into a sensitive sensing region and a semi-sensitive sensing region;

[0045] The sensitive sensing zone covers the spatial range of the end of the low-energy fission fragment range, that is, the position corresponding to the end of the low-energy fission fragment range from the beginning of the cathode sensing region.

[0046] The semi-sensitive region covers the spatial range of the alpha particle's range, that is, the position extending from the end of the sensitive region to the end of the alpha particle's range.

[0047] In this embodiment, the length of the sensitive sensing region is 15 mm, completely covering the maximum range of low-energy fission fragments, but less than the range of alpha particles. The length of the semi-sensitive sensing region along the drift direction is 60 mm, extending from the end of the sensitive sensing region to the termination end of the cathode sensing region, completely covering the range of alpha particles.

[0048] The differential sensing length is determined based on the spatial boundary between the sensitive region and the semi-sensitive region, and the differential sensing length and the non-uniform weighted potential cathode are obtained.

[0049] It is important to understand that the differential sensing length is defined as the distance from the boundary between the sensitive and semi-sensitive sensing regions to the beginning of the cathode sensing region. The differential sensing length can be adjusted by the size of the novel cathode, and its value is determined by the difference between the range of alpha particles and the range of fission fragments. In this embodiment, the differential sensing length is 15 mm, which is the length of the sensitive sensing region.

[0050] S2. In the weighted potential field established by the non-uniform weighted potential cathode, the induced charge distribution of the incident particle ionization trajectory in the drift direction is accumulated by position weighting, and the amplitude of the induced signal of each electrode is obtained by the summation result.

[0051] It is important to know that the non-uniform weighted potential cathode has different weighted potential values ​​at different positions in the drift direction. The contribution of the induced charge generated by the incident particle at each position of the ionization trajectory to the cathode induced signal is determined by the weighted potential value corresponding to that position. By accumulating the product of the induced charge and the weighted potential value at all positions, the spatial distribution information of the incident particle ionization trajectory is encoded into the amplitude of the cathode induced signal.

[0052] Specifically, the steps for performing the position-weighted accumulation include S2.1 to S2.3:

[0053] S2.1 Based on the weighted potential distribution of the non-uniform weighted potential cathode in the drift direction, the induced charge generated at each position on the ionization trajectory of the incident particle is multiplied one by one with the corresponding weighted potential value and summed to obtain the summation result.

[0054] The amount of induced charge generated is determined by the energy loss of the incident particle at that location. The weighted potential value is calculated by the finite element analysis method. The sum of the two values ​​after multiplying them bit by bit is the sum of the cathode induced signal. This sum contains information on the total ionization of the incident particle and the spatial distribution information of the ionization trajectory.

[0055] In this embodiment, the alpha particle ionization trajectory is discretized along the drift direction into 100 sampling positions consistent with the sub-interval division. Each sampling position corresponds to a carrier charge and a weighted potential value. Taking the sampling position with a normalized distance of 0.1 as an example, the weighted potential value corresponding to this position is 0.1. If the carrier charge generated at this position is Q, then the contribution of this position to the cathode summation result is 0.1 × Q.

[0056] The product results of all 100 sampling locations are summed sequentially to obtain the summation result of the cathode induced signal of the alpha particle.

[0057] S2.2 The time integral of the summation result over the carrier transit process is used as the induced signal waveform of each electrode.

[0058] The carrier transit process refers to the process by which electrons and ions generated by incident particles in the working gas drift toward the anode and cathode respectively under the action of an electric field. During the carrier transit process, the induced charge on each electrode accumulates continuously over time. By integrating the summation result over the carrier transit time, the complete waveform of the amplitude of the induced signal of each electrode as a function of time is obtained, which is the induced signal waveform of each electrode.

[0059] In this embodiment, electrons drift towards the anode under the influence of an electric field, while ions drift towards the cathode. The carrier transit time is approximately several microseconds. During the carrier transit process, the cathode induced signal waveform monotonically increases from zero with time, reaching its maximum value and stabilizing when the carrier transit is complete. The anode induced signal waveform behaves similarly. Time integration is performed on both the cathode and anode to obtain the cathode induced signal waveform and the anode induced signal waveform, respectively.

[0060] S2.3 Extract the waveform of the induction signal to obtain the amplitude of the induction signal of each electrode.

[0061] Reference Figure 2 As shown, specifically, the steps for extracting the waveform of the sensed signal include B1~B2:

[0062] B1. Set a trigger threshold for the waveform of the sensing signal, and search for the maximum value point within the time interval in which the waveform amplitude exceeds the trigger threshold.

[0063] The purpose of the trigger threshold is to distinguish the waveform of the induced signal generated by the effective particle event from the baseline noise, and to search for the maximum value point only within the time interval when the waveform amplitude exceeds the trigger threshold, thereby avoiding the misjudgment of noise fluctuations as the maximum value point of the effective signal.

[0064] The trigger threshold should be set higher than the maximum fluctuation of the baseline noise, while being lower than the amplitude of the induced signal waveform generated by the effective particle event.

[0065] In this embodiment, the root mean square amplitude of the baseline noise is measured to be approximately 5 mV, and the trigger threshold is set to 20 mV, which is 4 times the root mean square amplitude of the baseline noise, to ensure that the sensing signal waveform of the effective particle event can be reliably triggered, while the baseline noise does not trigger the search process.

[0066] Within a time interval where the waveform amplitude exceeds 20 mV, the maximum points of the cathode induction signal waveform and the anode induction signal waveform are searched respectively.

[0067] B2. Record the waveform amplitude value at the time corresponding to the maximum value point, and use the amplitude value as the amplitude of the induced signal of the corresponding electrode to obtain the amplitude of the induced signal of each electrode.

[0068] The maximum point corresponds to the moment when the carrier transition is completed. At this time, the induced charge accumulation on each electrode reaches its maximum value, and the waveform amplitude no longer increases with time. Therefore, the waveform amplitude value at the moment corresponding to the maximum point can fully reflect all the induced charge information generated by the incident particle on the ionization trajectory.

[0069] In this embodiment, a maximum point is found in the waveform of the cathode induction signal, and the waveform amplitude value at the time corresponding to the maximum point is recorded as the amplitude of the cathode induction signal.

[0070] The maximum point is found in the waveform of the anode induction signal, and the waveform amplitude value at the time corresponding to the maximum point is recorded as the amplitude of the anode induction signal. The amplitude of the induction signal of each electrode is obtained and used for the subsequent steps to construct the ionization distribution coefficient.

[0071] S3. Construct the ionization distribution coefficient based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude in the amplitude of each electrode induced signal.

[0072] The steps for constructing the ionization distribution coefficient include S3.1 to S3.3:

[0073] S3.1 Collect several sampling points of the waveform of the induced signal of each electrode, and calculate the average amplitude of the sampling points.

[0074] The amplitude mean is used to characterize the baseline level of the waveform of the induced signal of each electrode before the arrival of the effective signal.

[0075] Sampling points should be collected during the silent time interval before the trigger event occurs, when the induced signal waveform has not yet been affected by the ionization signal of the incident particles, and the average amplitude of the sampling points can accurately reflect the baseline bias level of each electrode. The number of sampling points should be sufficient to suppress the influence of random noise on the average amplitude, and the sampling time interval should fall entirely before the trigger event occurs.

[0076] In this embodiment, within a 2000 ns time interval before the trigger event occurs, 100 sampling points are collected for both the cathode and anode induction signal waveforms, and the average amplitude of the 100 sampling points is calculated. Taking the cathode as an example, the calculated average amplitude of the 100 sampling points is 3 mV, and taking the anode as an example, the calculated average amplitude of the 100 sampling points is 4 mV.

[0077] S3.2. Using the average amplitude as the baseline bias value of the corresponding electrode, subtract the baseline bias value of the corresponding electrode from the amplitude of the induced signal of each electrode to obtain the amplitude of the induced signal after baseline correction of each electrode.

[0078] The baseline bias value reflects the background level of each electrode in the absence of incident particles. If the baseline bias is not corrected, the amplitude of the induced signal of each electrode will be superimposed on the baseline bias value, causing the subsequent calculation result of the ionization distribution coefficient to deviate from the true value. The baseline bias values ​​of each electrode are independent of each other, and baseline correction needs to be performed separately for the cathode and anode.

[0079] For example, the cathode induced signal amplitude is 850 mV, the cathode baseline bias value is 3 mV, and the cathode baseline corrected induced signal amplitude is 850 mV - 3 mV = 847 mV;

[0080] The amplitude of the anode induced signal is 920 mV, the anode baseline bias is 4 mV, and the amplitude of the induced signal after anode baseline correction is 920 mV - 4 mV = 916 mV.

[0081] S3.3 Compare the baseline-corrected anode induction signal amplitude with the preset effective event energy threshold;

[0082] Specifically, the amplitude of the baseline-corrected anode induction signal is compared with a preset effective event energy threshold to screen for effective particle events.

[0083] In this embodiment, the effective event energy threshold is preset to 50 mV. The baseline-corrected anode induction signal amplitude of 916 mV is compared with the effective event energy threshold of 50 mV. If 916 mV is not lower than 50 mV, proceed to step S3.3.2.

[0084] S3.3.1 When the amplitude of the baseline-corrected anode induction signal is lower than the effective event energy threshold, the current event is marked as an invalid event and discarded.

[0085] When the amplitude of the baseline-corrected anode induction signal is lower than the effective event energy threshold, the current event is determined to be invalid, marked as invalid, and discarded. The ionization distribution coefficient is not calculated for the current event, and the process directly proceeds to the next particle event. Discarding invalid events avoids low-quality data contaminating the subsequent clustering distribution in the two-dimensional discrimination space, thus improving the accuracy of particle identification.

[0086] In this embodiment, if the amplitude of the anodic induction signal after baseline correction for an event is 30 mV, which is lower than the effective event energy threshold of 50 mV, the event is marked as an invalid event and discarded, and the ionization distribution coefficient of the event is not calculated.

[0087] S3.3.2 When the amplitude of the baseline-corrected anode induced signal is not lower than the effective event energy threshold, the ionization distribution coefficient of the current particle event is obtained by dividing the amplitude of the baseline-corrected cathode induced signal by the amplitude of the baseline-corrected anode induced signal.

[0088] When the amplitude of the baseline-corrected anode induction signal is not lower than the effective event energy threshold, the current event is determined to be an effective particle event. The ionization distribution coefficient of the current particle event is obtained by dividing the amplitude of the baseline-corrected cathode induction signal by the amplitude of the baseline-corrected anode induction signal.

[0089] It is also important to know that the amplitude of the cathode induced signal is determined by the positional accumulation of the non-uniform weighted potential cathode on the ionization trajectory of the incident particle, reflecting the proportion of ionization of the incident particle ionization trajectory within the differential induced length.

[0090] The amplitude of the anode induction signal reflects the total ionization of the incident particles in the working gas; the ratio of the two eliminates the influence of the total energy of the incident particles on the amplitude of the cathode induction signal, so that the ionization distribution coefficient is only related to the spatial distribution characteristics of the ionization trajectory of the incident particles.

[0091] In this embodiment, the baseline-corrected cathode induction signal amplitude is 847 mV, the baseline-corrected anode induction signal amplitude is 916 mV, and the ionization distribution coefficient of the current fission fragmentation event is 847 mV ÷ 916 mV ≈ 0.92. This ionization distribution coefficient, together with the baseline-corrected anode induction signal amplitude, will be used for the subsequent construction of the two-dimensional discrimination space and particle type discrimination.

[0092] S4. A two-dimensional discrimination space is constructed using the amplitude of the anode induction signal and the ionization distribution coefficient. Alpha particles and low-energy fission fragments form spatially separated clusters in the two-dimensional discrimination space. The incident particle types are classified according to their cluster affiliation.

[0093] The two-dimensional discrimination space uses the amplitude of the baseline-corrected anode induction signal as the horizontal axis and the ionization distribution coefficient as the vertical axis. Each particle event corresponds to a unique coordinate point in the two-dimensional discrimination space.

[0094] Because the ionization trajectory of the low-energy fission fragments falls completely within the sensitive response region, the amplitude of the cathode induced signal is strongly modulated by the weighted potential, and the ionization distribution coefficient is high.

[0095] The ionization trajectory of alpha particles crosses both the sensitive and semi-sensitive regions. The amplitude of the cathode-induced signal is modulated by the weighted potential to a lesser extent than that of low-energy fission fragments, and the ionization distribution coefficient is lower. Therefore, the two types of particles naturally form spatially separated cluster regions in the two-dimensional discrimination space.

[0096] Specifically, the steps for classifying the type of incident particles based on cluster affiliation include S4.1 to S4.4:

[0097] S4.1 Collect known alpha particle standard source event point sets and known fission fragment event point sets. Calculate the mean vector and covariance matrix of each alpha particle event point set and fission fragment event point set in the two-dimensional discriminant space to obtain their respective two-dimensional Gaussian distribution parameters.

[0098] The mean vector is composed of the mean coordinates of various event point sets in the horizontal and vertical directions, reflecting the cluster center position of this type of particle in the two-dimensional discriminant space;

[0099] The covariance matrix is ​​composed of the variances of event point sets along the horizontal axis, the variances along the vertical axis, and the covariances along both axes. It reflects the spatial distribution of the particle clustering regions and the correlation between the two axes. The two-dimensional Gaussian distribution parameters together determine the probability density distribution of each type of particle in the two-dimensional discriminant space.

[0100] In this embodiment, the mean vector of 1000 5 MeV alpha particle standard source event points is calculated to be (120 mV, 0.61), and the variance of the covariance matrix on the horizontal axis is 25 mV. 2 The variance of the vertical axis is 0.003, and the covariance of the horizontal and vertical axes is 0.08 mV.

[0101] The mean vector calculated for a set of 1000 low-energy fission fragmentation events at 5 MeV is (121 mV, 0.91), and the variance of the covariance matrix along the horizontal axis is 36 mV. 2 With a vertical axis variance of 0.006 and a horizontal and vertical axis covariance of 0.12 mV, the two-dimensional Gaussian distribution parameters of α particles and low-energy fission fragments were obtained.

[0102] S4.2. Using the curve formed by the intersection of the equal probability density lines of the two-dimensional Gaussian distribution parameters of α particles and the two-dimensional Gaussian distribution parameters of fission fragments as the initial discrimination boundary, calculate the total misclassification rate of the α particle event point set and the fission fragment event point set under the initial discrimination boundary.

[0103] The probability density functions of the two-dimensional Gaussian distribution parameters of alpha particles and fission fragments are established respectively. The equiprobability density lines of the two probability density functions intersect in the two-dimensional discrimination space to form a set of curves, which are used as the initial discrimination boundary.

[0104] The initial discrimination boundary divides the two-dimensional discrimination space into one side of the α-particle clustering region and one side of the fission fragment clustering region. The number of event points in the α-particle event point set and the fission fragment event point set that fall on the wrong side is counted. The total misclassification rate under the initial discrimination boundary is obtained by dividing the total number of misclassified event points by the total number of events in the two event point sets.

[0105] In this embodiment, the probability density functions of the two types of two-dimensional Gaussian distribution parameters obtained in step S4.1 are established, and the equiprobability density lines of the two probability density functions intersect in the two-dimensional discrimination space to form the initial discrimination boundary curve.

[0106] The number of 1000 alpha particle event points that fall on one side of the fission fragment cluster region is 18, and the number of 1000 fission fragment event points that fall on one side of the alpha particle cluster region is 22. The total misclassification rate is (18 + 22) ÷ 2000 = 2.0%.

[0107] S4.3 Iteratively correct the initial discrimination boundary until the total classification misclassification rate converges to the minimum value, and solidify the converged discrimination boundary into the classification boundary of the two-dimensional discrimination space.

[0108] Using the total misclassification rate obtained in step S4.2 as the optimization objective, the initial discrimination boundary is iteratively corrected. In each iteration, the position and morphological parameters of the initial discrimination boundary are adjusted, and the total misclassification rate of the α-particle event set and the fission fragment event set under the adjusted discrimination boundary is recalculated. If the total misclassification rate is lower than the result of the previous iteration, the result of this adjustment is retained; otherwise, it is rolled back and readjusted with a smaller step size.

[0109] Repeat the above process until the change in the total classification misclassification rate between two adjacent iterations is lower than the preset convergence threshold. Once the total classification misclassification rate has converged to the minimum value, solidify the converged discrimination boundary as the classification boundary of the two-dimensional discrimination space.

[0110] For example, with a preset convergence threshold of 0.01%, iterative correction is performed starting from an initial total classification misclassification rate of 2.0%. After 15 iterations, the change in the total classification misclassification rate between two adjacent iterations decreases to 0.008%, which is lower than the convergence threshold of 0.01%, and convergence is determined. At this point, the total classification misclassification rate is 0.85%, and the discrimination boundary obtained in the 15th iteration is solidified as the classification boundary of the two-dimensional discrimination space.

[0111] S4.4 Determine the coordinate position formed by the amplitude of the anodic induction signal and the ionization distribution coefficient corresponding to the particle event to be tested in the two-dimensional discrimination space, determine the relative relationship between the coordinate position and the classification boundary, and determine the particle to be tested whose coordinate position falls on one side of the α particle clustering region of the classification boundary as α particle, and determine the particle to be tested whose coordinate position falls on one side of the fission fragment clustering region of the classification boundary as fission fragment.

[0112] For the particle event to be tested, the amplitude of the anodic induction signal after baseline correction obtained in step S3 is used as the horizontal axis coordinate and the ionization distribution coefficient obtained in step S3.3.2 is used as the vertical axis coordinate. The coordinate position of the particle event to be tested is determined in the two-dimensional discrimination space. The relative relationship between the coordinate position and the classification boundary solidified in step S4.3 is judged. The particle to be tested whose coordinate position falls on one side of the α particle clustering region of the classification boundary is determined to be an α particle, and the particle to be tested whose coordinate position falls on one side of the fission fragment clustering region of the classification boundary is determined to be a fission fragment.

[0113] In this embodiment, the baseline-corrected anode induction signal amplitude of a certain particle event to be tested is 130 mV, the ionization distribution coefficient is 0.89, and the corresponding coordinate position in the two-dimensional discrimination space is (130 mV, 0.59). The relative relationship between this coordinate position and the classification boundary is determined. (130 mV, 0.59) falls on one side of the α particle clustering region of the classification boundary, and the particle to be tested is determined to be an α particle.

[0114] The baseline-corrected anode induction signal amplitude of another particle event is 126 mV, and the ionization distribution coefficient is 0.92. The corresponding coordinate position in the two-dimensional discrimination space is (126 mV, 0.92). The relative relationship between this coordinate position and the classification boundary is determined. (126 mV, 0.92) falls on one side of the fission fragment clustering region of the classification boundary. Therefore, the particle to be tested is identified as a fission fragment.

[0115] Example 3 is an embodiment of the present invention, which provides a novel cathode structure design for a fission ionization chamber and a particle identification system, including a fission ionization chamber, a signal acquisition unit, a processing unit, and a classification and identification unit;

[0116] The fission ionization chamber is equipped with an anode and a non-uniform weighted potential cathode. The sensing region of the non-uniform weighted potential cathode is constructed non-uniformly based on the range difference of alpha particles and fission fragments in the working gas of the ionization chamber, forming a partitioned structure with different sensing lengths, so as to form a weighted potential field in the sensitive area of ​​the ionization chamber.

[0117] The signal acquisition unit is used to synchronously acquire the anode induction signal output by the anode and the cathode induction signal output by the non-uniform weighted potential cathode.

[0118] The processing unit is used to perform position-weighted accumulation of the induced charge distribution of the incident particle ionization trajectory along the charge drift direction to obtain the amplitude of the cathode induced signal and the amplitude of the anode induced signal; and to calculate the ionization distribution coefficient based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude.

[0119] The classification and identification unit is used to construct a two-dimensional discrimination space composed of the amplitude of the anode induction signal and the ionization distribution coefficient; and to determine the type of incident particle based on the clustering regions in the two-dimensional discrimination space where α particles and fission fragments are separated from each other.

[0120] This embodiment also provides a computer device applicable to a novel cathode structure design and particle identification method for a fission ionization chamber, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the novel cathode structure design and particle identification method for a fission ionization chamber as proposed in the above embodiment.

[0121] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a novel cathode structure design for a fission ionization chamber and a particle identification method as proposed in the above embodiments.

[0122] The storage medium proposed in this embodiment belongs to the same inventive concept as the novel cathode structure design and particle identification method for fission ionization chamber proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0123] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0124] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A novel cathode structure design for a fission ionization chamber and a particle identification method, characterized in that, Includes the following steps: By taking the range difference between alpha particles and low-energy fission fragments in the working gas as a constraint, the cathode structure is specially designed and the cathode induction region is non-uniformly induction constructed to obtain the differential induction length and non-uniform weighted potential cathode. In the weighted potential field established by the non-uniform weighted potential cathode, the induced charge distribution of the incident particle ionization trajectory in the drift direction is accumulated by position weighting, and the amplitude of the induced signal of each electrode is obtained by the summation result. An ionization distribution coefficient is constructed based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude in the amplitude of each electrode induced signal. A two-dimensional discrimination space is constructed using the amplitude of the anode induction signal and the ionization distribution coefficient. Alpha particles and low-energy fission fragments form spatially separated clusters in the two-dimensional discrimination space, and the incident particle types are classified according to their cluster affiliation.

2. The novel cathode structure design and particle identification method for a fission ionization chamber as described in claim 1, characterized in that, The steps for constructing the non-uniform induction include: The cathode sensing region is divided into a sensitive sensing region and a semi-sensitive sensing region along the drift direction; Among them, the sensitive response region covers the spatial range of the end of the low-energy fission fragment range, and the semi-sensitive response region covers the spatial range of the alpha particle range. The differential sensing length is determined based on the spatial boundary between the sensitive region and the semi-sensitive region. The differential sensing length can be adjusted by the size of the novel cathode to obtain the differential sensing length and the non-uniform weighted potential cathode.

3. The novel cathode structure design and particle identification method for a fission ionization chamber as described in claim 2, characterized in that, The steps for performing the location-weighted accumulation include: Based on the weighted potential distribution of the non-uniform weighted potential cathode in the drift direction, the induced charge generated at each position on the ionization trajectory of the incident particle is multiplied one by one with the corresponding weighted potential value and summed to obtain the summation result. The summation result is integrated over time with the carrier transit process as the induced signal waveform of each electrode; The waveform of the induced signal is extracted to obtain the amplitude of the induced signal of each electrode.

4. The novel cathode structure design and particle identification method for a fission ionization chamber as described in claim 3, characterized in that, The steps for extracting the waveform of the sensed signal include: A trigger threshold is set for the waveform of the sensing signal, and a maximum value point is searched within the time interval in which the waveform amplitude exceeds the trigger threshold. Record the waveform amplitude value at the time corresponding to the maximum point, and use the amplitude value as the amplitude of the induced signal of the corresponding electrode to obtain the amplitude of the induced signal of each electrode.

5. The novel cathode structure design and particle identification method for a fission ionization chamber as described in claim 4, characterized in that, The steps for dividing the cathode induction region include: The cathode weight potential is constructed non-uniformly, so that the cathode weight potential is very low in the region far from the cathode, close to 0; while in a small region around the cathode, the weight potential rapidly increases to 1. The cathode induction region with a weighted potential greater than 0.5 is divided into the sensitive response region; The cathode induction region with a weighted potential less than 0.5 is divided into a semi-sensitive region. The size of the sensitive area and the semi-sensitive area can be adjusted by the differential sensing length.

6. The novel cathode structure design and particle identification method for a fission ionization chamber as described in claim 5, characterized in that, The steps for constructing the ionization distribution coefficient include: Collect several sampling points of the waveform of the induced signal from each electrode, and calculate the average amplitude of the sampling points; Using the average amplitude as the baseline bias value of the corresponding electrode, the baseline bias value of the corresponding electrode is subtracted from the amplitude of the induced signal of each electrode to obtain the baseline-corrected amplitude of the induced signal of each electrode. The baseline-corrected amplitude of the anode induction signal is compared with a preset effective event energy threshold. If the amplitude of the baseline-corrected anode sensing signal is lower than the effective event energy threshold, the current event is marked as an invalid event and discarded. If the amplitude of the baseline-corrected anode induced signal is not lower than the effective event energy threshold, the ionization distribution coefficient of the current particle event is obtained by dividing the amplitude of the baseline-corrected cathode induced signal by the amplitude of the baseline-corrected anode induced signal.

7. The novel cathode structure design and particle identification method for a fission ionization chamber as described in claim 6, characterized in that, The steps for classifying incident particle types based on cluster affiliation include: Collect known alpha particle standard source event point sets and known fission fragment event point sets. Calculate the mean vector and covariance matrix of the alpha particle event point set and the low-energy fission fragment event point set in the two-dimensional discrimination space to obtain their respective two-dimensional Gaussian distribution parameters. The curve formed by the intersection of the equiprobability density lines of the two-dimensional Gaussian distribution parameters of alpha particles and the two-dimensional Gaussian distribution parameters of low-energy fission fragments is used as the initial discrimination boundary. The total misclassification rate of the alpha particle event point set and the low-energy fission fragment event point set under the initial discrimination boundary is calculated. The initial discrimination boundary is iteratively corrected until the total classification misclassification rate converges to the minimum value, and the converged discrimination boundary is solidified as the classification boundary of the two-dimensional discrimination space; In the two-dimensional discrimination space, the coordinate position formed by the amplitude of the anodic induction signal and the ionization distribution coefficient corresponding to the particle event to be tested is determined. The relative relationship between the coordinate position and the classification boundary is determined. The particle to be tested whose coordinate position falls on one side of the α particle clustering region of the classification boundary is determined as an α particle, and the particle to be tested whose coordinate position falls on one side of the low-energy fission fragment clustering region of the classification boundary is determined as a low-energy fission fragment.

8. A novel cathode structure design and particle identification system for a fission ionization chamber, employing the novel cathode structure design and particle identification method for a fission ionization chamber as described in any one of claims 1-7, characterized in that, include: Fission ionization chamber, signal acquisition unit, computing and processing unit, and classification and identification unit; The fission ionization chamber is equipped with an anode and a non-uniform weighted potential cathode. The sensing region of the non-uniform weighted potential cathode is constructed non-uniformly based on the range difference of alpha particles and low-energy fission fragments in the working gas of the ionization chamber, forming a partitioned structure with different sensing lengths, so as to form a weighted potential field in the sensitive area of ​​the ionization chamber. The signal acquisition unit is used to synchronously acquire the anode induction signal output by the anode and the cathode induction signal output by the non-uniform weighted potential cathode. The processing unit is used to perform position-weighted accumulation of the induced charge distribution of the incident particle ionization trajectory along the charge drift direction to obtain the amplitude of the cathode induced signal and the amplitude of the anode induced signal; and to calculate the ionization distribution coefficient based on the ratio of the cathode induced signal amplitude to the anode induced signal amplitude. The classification and identification unit is used to construct a two-dimensional discrimination space composed of the amplitude of the anode induction signal and the ionization distribution coefficient; and to determine the type of incident particles based on the clustering regions in the two-dimensional discrimination space where alpha particles and low-energy fission fragments are separated from each other.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the novel cathode structure design and particle identification method for a fission ionization chamber as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the novel cathode structure design and particle identification method for a fission ionization chamber as described in any one of claims 1 to 7.

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