A method for pulse signal screening and signal quality evaluation

Abstract

The present invention discloses a method for pulse signal screening and signal quality evaluation, comprising the following steps: S1, obtaining a nuclear pulse index signal and determining the time width of a single signal; S2, calculating the average value of the signal amplitude within a single time width; S3, calculating the variance of the signal amplitude within a single time width; S4, drawing a scatter plot of the average and variance of all signals, and fitting a quadratic function curve to the scatter plot; S5, implementing screening of abnormal signals and signal quality evaluation through the scatter plot distribution. The present invention screens signals by calculating the average and variance of a standard nuclear pulse signal within a single signal width, requiring fewer computational resources. The type of abnormal signal is determined by the relative position of the scatter points of the signal mean and variance and the quadratic function curve fitted to its scatter distribution. This determination method is simple and does not require a complex algorithm program.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal screening, and in particular relates to a method for pulse signal screening and signal quality evaluation. Background Art

[0002] The output signal of a nuclear radiation detector is a series of voltage or current pulses with varying amplitudes, non-uniform waveforms, and random temporal distribution. These pulses are determined by the properties of the incident particles and the detector's response. Information about nuclear radiation and particles can be obtained from these pulses and their associated parameters. However, various interference factors during the detector's measurement process can alter the shape of the pulse signal, affecting the quality of the acquired energy spectrum. How to identify abnormal waveforms based on these pulse waveform variations and improve the quality of the detector's output signal is a critical technical challenge.

[0003] Current methods for signal identification and judgment include visual observation using digital sampling equipment or screening using back-end digital processing.

[0004] By connecting the detector signal output terminal to the digital sampling device terminal, the signal status can be directly observed. Connect an oscilloscope to the detector signal output terminal, and then adjust the oscilloscope sampling rate, window area and trigger mode to directly observe the signal status on the screen. The normal signal is a standard exponential decay signal such as Figure 1 As shown, the signal is expressed as a fast rising edge and a slow falling edge, and the signal has a certain time width. The digital sampling device can intuitively display the voltage signal (waveform) that changes over time, and observe and judge the detector output signal status in real time, identifying abnormal signals.

[0005] With the advancement of signal processing technology and computer science, the advantages of using digital methods to process pulse signals have been realized. Different mathematical methods are designed for waveform identification and screening for different types of abnormal signals, including filtering algorithms, noise reduction algorithms, pile-up recognition algorithms, etc. These algorithms can process and screen the output pulses according to different abnormal waveform characteristics, thereby improving the quality of the output signal.

[0006] However, directly observing waveform changes through digital sampling devices requires the observer to possess a certain level of waveform discrimination ability, and when the count rate is high, visual judgment is prone to missed and misjudgment. Using various algorithms to screen signals requires complex mathematical algorithms, and different digital processing methods are required to judge different types of abnormal signals. This makes such screening methods more cumbersome, and their resolution and screening effectiveness are insufficient. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for pulse signal screening and signal quality evaluation, which mainly solves the problems that the existing signal screening methods are relatively complicated, and have poor resolution and screening effects.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for pulse signal screening and signal quality evaluation comprises the following steps:

[0010] S1, obtaining a nuclear pulse index signal and determining the time width of a single signal; wherein the nuclear pulse index signal is a voltage signal output by the detector that varies with time when measuring in a radiation field;

[0011] S2, calculates the average value of the signal amplitude within a single time width;

[0012] S3, calculates the variance of the signal amplitude within a single time width;

[0013] S4, draw a scatter plot of the mean and variance of all signals, and perform quadratic function curve fitting on the scatter plot;

[0014] S5, screen out abnormal signals and evaluate signal quality through scatter plot distribution.

[0015] Furthermore, in step S1, the waveform data of the nuclear pulse index signal is acquired through a waveform acquisition module, and the waveform expression of a single nuclear pulse signal is:

[0016]

[0017] Among them, A1 and A2 are coefficient factors, k1 and k2 are time constants of the signal, which determine the time width T of a single nuclear pulse signal.

[0018] Furthermore, in step S2, the calculation formula for the average value M of the signal amplitude within a single time width is:

[0019]

[0020] Furthermore, in step S3, the calculation formula of the variance D of the signal amplitude within a single time width is:

[0021]

[0022]

[0023] Furthermore, in step S4, the scatter plot is drawn with the mean value M as the X-axis coordinate and the variance D as the Y-axis coordinate; wherein the variance D of a single nuclear pulse signal and its mean value M satisfy the following relationship:

[0024] D∝M 2 .

[0025] Furthermore, in the screening process of step S5, abnormal signals are screened by using the relative distance d between the variance of the measured signal and the Y value of the fitting curve when the mean value is the same. When the signal mean value is determined, an abnormal signal is considered when the variance of the signal and the Y value of the fitting curve when the mean value is the same as d, wherein the relative distance d is the accuracy value of the set standard signal screening.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This method screens signals by calculating the mean and variance of a standard nuclear pulse signal within a single signal width, requiring fewer computational resources. Abnormal signal identification: The type of abnormal signal is determined by the relative position of the signal's mean and variance scatter points and the quadratic function curve fitted to their scatter point distribution. This simple method does not require complex algorithms. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an intentional waveform of a single nuclear pulse signal in an embodiment of the present invention.

[0029] Figure 2 It is a scatter plot of the signal mean and variance distribution and a fitting curve in an embodiment of the present invention.

[0030] Figure 3 This is a standard signal area diagram in an embodiment of the present invention.

[0031] Figure 4 This is a diagram of signal points in a standard signal area and signal points that deviate from the standard area in an embodiment of the present invention.

[0032] Figure 5 This is a waveform diagram of abnormal signals obtained through screening in an embodiment of the present invention.

[0033] Figure 6 This is a standard pulse signal waveform diagram actually measured in an embodiment of the present invention.

[0034] Figure 7 The figure shows the scatter plot distribution and fitting curve of the mean and variance of 10,000 groups of signals within 30 μs in an embodiment of the present invention.

[0035] Figure 8 This is a waveform diagram of some abnormal signals that deviate from the fitting curve obtained in an embodiment of the present invention.

[0036] Figure 9 This is a scatter plot of standard signal screening within a fitting curve distance of 0.002 in the embodiment of the present invention.

[0037] Figure 10 This is a scatter plot of standard signal screening within 0.001 of the fitting curve distance in the embodiment of the present invention.

[0038] Figure 11 This is a schematic diagram of the energy spectrum obtained by comparing the energy spectrum of the standard signal with a distance of 0.001 with the energy spectrum obtained by the original signal in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and examples. The embodiments of the present invention include but are not limited to the following examples.

[0040] Example

[0041] The present invention discloses a method for pulse signal screening and signal quality evaluation, comprising the following steps:

[0042] (1) Obtain the nuclear pulse index signal and determine the time width of a single signal.

[0043] The nuclear pulse index signal is a voltage signal that changes with time and is output by the detector when measuring in the radiation field. The waveform data can be obtained through a waveform acquisition module such as a digital sampling device. Figure 1 is a single nuclear pulse signal waveform, which can be expressed by the following formula:

[0044]

[0045] Where A1 and A2 are coefficient factors, k1 and k2 are time constants of the signal, and determine the time width T of a single nuclear pulse signal. The signal width is defined as the time width from the baseline amplitude rising to the maximum value and then returning to the baseline.

[0046] (2) Calculate the average value of the signal amplitude within a single time width.

[0047] Starting from the moment the signal is generated, the average value M of the signal amplitude in a single time width T is calculated. The calculation formula is:

[0048]

[0049] (3) Calculate the variance of the signal amplitude within a single time width.

[0050]

[0051]

[0052] (4) Draw a scatter plot of the mean and variance of all signals, and perform quadratic function curve fitting on the scatter plot.

[0053] Since the variance D of a single ideal signal and its mean M satisfy the following relationship

[0054] D∝M 2 .

[0055] The ideal signal's mean and variance scatter points should be distributed near the fitting curve. Figure 2 The quadratic function fitting curve results of the scatter plot of 10,000 sets of signals measured by the scintillator detector are drawn, with the mean as the X-axis coordinate and the variance as the Y-axis coordinate.

[0056] (5) Screening of abnormal signals and evaluation of signal quality are achieved through scatter plot distribution.

[0057] Abnormal signal measurements due to other factors during the measurement process can deviate from the detector's standard fitting curve. Abnormal signals are screened by measuring the relative distance between the measured signal's variance and the Y value of the fitting curve when the mean is the same. When the signal mean is determined, an abnormal signal is identified when the difference between the signal's variance and the Y value of the fitting curve when the mean is the same is greater than d. Figure 3 Curves 2 and 3 represent the signals when fitting curve C1 is shifted up and down by d, respectively. The area between curves 2 and 3 represents the standard signal region, which allows for signal screening. This region determines the proportion of standard signals relative to the total signal. A higher proportion of standard signals indicates higher detector output signal quality. Adjusting the value of d can improve the accuracy of standard signal screening. Figure 4 This is the abnormal signal screening result. The signal points in the standard signal area are Figure 4 (a), the signal point deviating from the standard area is Figure 4 (b), the abnormal signal data points obtained by screening can be used to draw the abnormal signal waveform as shown in Figure 5 .

[0058] Specifically, the method described in this embodiment is used to screen and judge the nuclear pulse index signal of a scintillator detector, and 10,000 groups of signals obtained by measuring the moderated Am-Be neutron source are analyzed. Figure 6 It is a standard pulse signal actually measured, with a time width within 30μs; Figure 7 The scatter plot distribution and fitting curve of the mean and variance of 10,000 sets of signals within 30 μs; Figure 8 It is the abnormal signal that deviates from the fitting curve; Figure 9 For standard signal screening within the fitting curve distance of 0.002, the proportion of standard signals is 85.91%; Figure 10 Standard signals were screened within a distance of 0.001 from the fitting curve, and the proportion of standard signals was 73.8%. Figure 11The energy spectrum obtained for the standard signal with a distance of 0.001 was compared with the energy spectrum obtained for the original signal. The thermal neutron peak energy resolution was improved by 0.6%. The results show that this method can effectively distinguish abnormal signals and evaluate the quality of the detector output signal.

[0059] The above embodiment is only one of the preferred implementation methods of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications that have no substantive meaning made to the main design concept and spirit of the present invention, as long as the technical problems solved are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. A method for pulse signal screening and signal quality evaluation, characterized in that: The following steps are involved: S1, obtaining a nuclear pulse index signal and determining the time width of a single signal; wherein the nuclear pulse index signal is a voltage signal output by the detector that varies with time when measuring in a radiation field; S2, calculates the average value of the signal amplitude within a single time width; S3, calculates the variance of the signal amplitude within a single time width; S4, draw a scatter plot of the mean and variance of all signals, and perform quadratic function curve fitting on the scatter plot; wherein, the scatter plot is drawn with the mean M as the X-axis coordinate and the variance D as the Y-axis coordinate; wherein, the variance D of a single nuclear pulse signal and its mean M satisfy the following relationship: D∝M 2 ; S5, screen out abnormal signals and evaluate signal quality through scatter plot distribution; wherein, during the screening process, abnormal signals are screened by using the relative distance d between the variance of the measured signal and the Y value of the fitting curve when the mean value is the same. When the mean value of the signal is determined, an abnormal signal is considered when the variance of the signal and the Y value of the fitting curve when the mean value is the same as d. wherein the relative distance d is the set accuracy value of the standard signal screening.

2. A pulse signal screening and signal quality evaluation method according to claim 1, characterized in that: In step S1, the waveform data of the nuclear pulse index signal is acquired through a waveform acquisition module. The waveform expression of a single nuclear pulse signal is: Among them, A1 and A2 are coefficient factors, k1 and k2 are time constants of the signal, which determine the time width T of a single nuclear pulse signal.

3. A pulse signal screening and signal quality evaluation method according to claim 2, characterized in that: In step S2, the calculation formula for the average value M of the signal amplitude within a single time width is:

4. A pulse signal screening and signal quality evaluation method according to claim 3, characterized in that: In step S3, the calculation formula of the variance D of the signal amplitude within a single time width is:

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