A portable gamma spectrum measurement system and method

Abstract

The present invention discloses a portable gamma spectrum measurement system, comprising a gamma signal detector, a signal conditioning circuit, an ADC digital acquisition circuit, a ZYNQ digital signal processing module, and a display module. The signal conditioning circuit is connected to the gamma signal detector and the ADC digital acquisition circuit, respectively. The ADC digital acquisition circuit is connected to the ZYNQ digital signal processing module, and finally to the display module for spectrum display. The present invention utilizes a flat-top expandable peak shaping method proposed by a recursive equation to first deconvolve the input negative exponential signal into a pulse signal, which is then synthesized into a flat-top peak shape through convolution, thereby accurately extracting the peak value of the negative exponential signal. The system utilizes a ZYNQ chip integrating an FPGA and an ARM processor, achieving hardware miniaturization, making the entire system compact, lightweight, and easy to carry and operate.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear radiation detection, and in particular relates to a portable gamma energy spectrum measurement system and a method thereof. Background Art

[0002] With increasing concern about radiation safety, radiation can cause serious consequences such as cancer and genetic mutations. Among radiation sources, gamma rays are the most penetrating, making gamma spectroscopy measurements crucial. Gamma spectroscopy provides crucial information for structural research, radionuclide identification, nuclear reaction analysis, material composition analysis, and radiation dose assessment. Existing gamma spectroscopy measurement systems primarily consist of traditional desktop instruments and portable devices. Traditional desktop instruments typically offer high performance and accuracy, but their bulk and complex operation make them unsuitable for portability and real-time measurement, limiting their application. Meanwhile, existing portable gamma spectroscopy instruments, while portable, often suffer from low sensitivity and poor spectral resolution due to technical limitations, failing to meet the demands for precise monitoring and analysis of radiation sources.

[0003] In summary, existing portable gamma spectroscopy measurement equipment has the following disadvantages:

[0004] 1. Limited sensitivity: Due to the limitations of detector size and material selection, the sensitivity is insufficient and low-intensity gamma-ray radiation cannot be accurately measured.

[0005] 2. Low energy spectrum resolution: Existing algorithms and technologies are unable to effectively improve the energy spectrum resolution, resulting in difficulty in clearly distinguishing energy peaks in the energy spectrum, affecting the accurate identification and analysis of radiation sources.

[0006] 3. Complex data processing: In existing technologies, the data processing process is relatively complex and takes a long time to obtain the final energy spectrum results, which is not suitable for real-time monitoring application scenarios.

[0007] 4. High energy consumption: While improving sensitivity and resolution, some portable devices also increase energy consumption, resulting in limited device usage time. Summary of the Invention

[0008] The purpose of the present invention is to implement a flat-top peak filtering shaping algorithm on the ZYNQ-7000 series platform integrating FPGA and ARM processor. This method is superior to other traditional filtering shaping methods in solving system ballistic loss, pile-up identification, anti-interference ability, etc. By introducing a flat-top expandable peak shaping method proposed by recursive equations, fast digital signal processing can be performed on the FPGA to achieve efficient and real-time system performance. At the same time, due to the extremely high integration of the ZYNQ chip and other devices used, it can be portable. Through this system and method, users can quickly and accurately obtain the energy spectrum information of gamma rays, realize timely monitoring and analysis of radiation sources, and have important application value.

[0009] In order to solve the above technical problems and achieve the above technical effects, the present invention designs a portable gamma spectrum measurement system, including: a gamma signal detector, a signal conditioning circuit, an ADC digital acquisition circuit, a ZYNQ digital signal processing module and a display module; the signal conditioning circuit is respectively connected to the gamma signal detector and the ADC digital acquisition circuit; the ADC digital acquisition circuit is connected to the ZYNQ digital signal processing module, and finally connected to the display module for spectrum display; the ZYNQ digital signal processing module integrates FPGA and ARM processor; in the FPGA part of the ZYNQ chip, an energy spectrum data processing algorithm is designed, which mainly includes functional modules such as a digital filtering shaping module, a pile-up rejection module, a baseline estimation module, an amplitude extraction module, and an energy spectrum generation module; and the digital filtering shaping module is optimized: the analog signal of the gamma signal nuclear detector is converted into a digital signal through conditioning, the continuous time signal is digitized, and the digital signal generated by discrete time convolution is defined as x(n), that is:

[0010]

[0011] where a = e -ΔT / τ , and 0<a<1, ΔT is the sampling interval of ADC, the exponential base a of the digital exponential signal is related to the decay time constant τ of the signal, and the ratio of two consecutive values ​​can be expressed as:

[0012]

[0013] Where n>0, and x(n)=1, so the deconvolution recursive formula of x(n) can be expressed as:

[0014] x(n)=δ(n)+ax(n-1)

[0015] Where δ(n) represents the discrete impulse signal;

[0016] The core of the digital synthesis flat-peak pulse shaping method is to separate and accumulate the corresponding parts of the impulse response after the expansion of x(n) multiple times, and finally synthesize the final peak pulse shape through delay. The time domain expression can be expressed as the following piecewise function:

[0017]

[0018] where n c =n a +n b , n a =t a / ΔT、n b =t b / ΔT、n c =t c / ΔT,t a , t b , t c They are the rise time of the peak forming, the sum of the rise time and the flat top time, and the peak forming time; when n a -n b =0, the flat top time is 0;

[0019] The flat-peak pulse shaping algorithm, which is formed by the third-order polynomial by four consecutive accumulations of the unit pulse δ(n), can be expressed by the following recursive formula:

[0020] h 3 (n) = h 3 (n-1)+δ(n)-δ(nn a )-δ(nn b -2)+δ(nn c -2)

[0021] h 2 (n) = h 2 (n-1)+h 3 (n)-n a [δ(nn a )-δ(nn b -1)]

[0022]

[0023] h(n)=h(n-1)+h 1 (n)

[0024] The original impulse function x(n) is deconvolved to obtain the impulse signal δ(n), and then δ(n) is synthesized into h through the first accumulation. 3 (n), after the second accumulation, a symmetrical triangular pulse h is synthesized 2 (n), after three accumulations, the bipolar pulse h is obtained 1(n), and finally the fourth accumulation is performed to obtain the final flat-top peak pulse shape h(n).

[0025] Furthermore, there is at least one gamma signal detector;

[0026] A method for measuring gamma spectrum using the gamma spectrum combined detection system as described above comprises the following steps:

[0027] S1: Select a high-sensitivity gamma-ray detector unit: Based on application requirements, select a silicon detector or NaI detector as the sensor for energy spectrum measurement; configure a fast ADC module: select a high-speed ADC for data sampling to improve the frequency and accuracy of data acquisition; integrate a ZYNQ chip: select a high-performance ZYNQ chip with integrated FPGA and ARM processor for real-time data processing and control;

[0028] S2: Data acquisition and preprocessing: The gamma-ray signal is converted from the detector into an electrical signal and sent to a fast ADC for high-speed sampling. The collected raw data is then preprocessed, including energy scaling and noise filtering, to improve the accuracy of subsequent data analysis. S5: Data preprocessing: The collected raw data is preprocessed, including energy scaling and noise filtering, to improve the accuracy of subsequent data analysis.

[0029] S3: FPGA design;

[0030] S4: Energy spectrum analysis: After FPGA algorithm optimization, the data is searched for peak positions, the positions of the peaks in the energy spectrum are determined, and the peak areas are calculated. Based on the peak search results, the energy spectrum peaks are integrated, and the energy spectrum peak areas are calculated to reflect the intensity of the radiation source.

[0031] S5: Result display and storage: The energy spectrum analysis results are displayed in real time on the portable display screen through the display unit for users to view; and the original data and analysis results are stored in the internal memory or external storage medium to facilitate subsequent data playback and further analysis.

[0032] The present invention has the following beneficial effects: by introducing a flat-top expandable peak shaping method proposed by a recursive equation, the present invention first deconvolves the input negative exponential signal into a pulse signal, which is then synthesized into a flat-top peak shape through convolution, thereby accurately extracting the peak value of the negative exponential signal. The system uses a ZYNQ chip integrating an FPGA and an ARM processor, achieving hardware miniaturization and making the entire system small, lightweight, and easy to carry and operate. The high-performance computing power of the FPGA and the rapid response of the ARM processor enable the system to collect and analyze gamma-ray energy spectrum data in real time. The system is suitable for use in fields such as nuclear energy and environmental protection, and has broad application prospects in nuclear power plants and radiation monitoring stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0034] Figure 1 This is a structural diagram of a portable gamma spectrum measurement system;

[0035] Figure 2 A transfer function model for sharp pulse shaping in a portable gamma spectroscopy measurement system.

[0036] Figure 3 To test the effect of digital energy spectrum system based on peak flat-top filtering method;

[0037] Figure 4 This is a comparison chart of the counting rates of different shaping algorithms of the present invention. DETAILED DESCRIPTION

[0038] Example 1

[0039] In this embodiment, the scintillator detector 137Cs energy spectrum experimental measurement is carried out. When conducting the experiment, a NaI (Tl) scintillator detector is selected and placed at a distance of 10 cm from the top center of the detector. 137 Cs radioactive source measurement, the measurement time is 10 minutes; and multiple measurements are performed to obtain 137 The energy spectrum measurement results of Cs were used to test the system stability, using the channel addresses corresponding to the characteristic peaks as test objects. The results are shown in Table 1. The total number of channel addresses in the system is 4096, and the average channel address across 9 tests is 2548, with only 10 channel addresses deviating, indicating that the system has good stability.

[0040] Table 1 Digital spectrum system measurement 137 Cs characteristic peak location

[0041]

[0042] Example 2

[0043] In this embodiment, if Figure 2 As shown in the figure, it can be seen Figure 2 The structure of the flat-top peak pulse shaping system based on the expansion-synthesis technology is described in the paper. The detector analog signal is usually conditioned and applied to the digital ADC to be converted into a discrete time signal; the process of digital pulse shaping is achieved by the following steps: first, the digitized analog signal is expanded (deconvolved) and then the pulse response of the desired pulse shape is synthesized.

[0044] Example 3

[0045] In this embodiment, if Figure 3 、 Figure 4 As shown, Figure 3 This is the energy spectrum obtained after measuring the NaI(Tl) scintillator detector for 10 minutes; when testing different shaping algorithms, the test is carried out at different times. 137 The channel count values ​​corresponding to the Cs characteristic peak are compared with their counting rate passability. Figure 4 The results shown in the figure show that, under low counting rate conditions, the triangle shaping algorithm outperforms the other three algorithms, followed by the flat top peak pulse shaping algorithm, which is slightly lower than the triangle shaping algorithm; however, under high counting rate conditions, the flat top peak pulse shaping algorithm proposed in the present invention has a higher counting rate passability than the other three algorithms; considering both the energy resolution and the counting rate passability, the flat top peak pulse shaping algorithm shows better performance.

[0046] The specific usage principle of the present invention is: first, turn on the system power and start the system. After the system initialization is completed, it enters the standby state; then the gamma signal detector is aimed at the sample to be tested or the target area, and the detector starts to receive gamma ray radiation; when the detector senses the gamma ray, the original signal is transmitted to the data acquisition module; the data acquisition module converts the original signal into a digital signal and transmits it to the signal processing unit, and the signal processing unit preprocesses and filters the digital signal to improve the signal quality; the preprocessed signal is transmitted to the data processor, and the data processor runs the built-in algorithm to analyze the signal to obtain the energy spectrum information of the gamma ray; the energy spectrum information is then displayed to the user in real time through the display screen, and the user can intuitively understand the current measurement results; the user can record the energy spectrum data as needed, or export the data to other devices through the system interface for further analysis and storage; after the measurement is completed, the user turns off the system power to complete the measurement process.

[0047] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all details in detail, nor do they limit the invention to only the specific implementation methods described.

Claims

1. A portable gamma spectrum measurement system, characterized in that: include: γ signal detector, signal conditioning circuit, ADC digital acquisition circuit, ZYNQ digital signal processing module and display module; the signal conditioning circuit is connected to the γ signal detector and ADC digital acquisition circuit respectively; the ADC digital acquisition circuit is connected to the ZYNQ digital signal processing module, and finally connected to the display module for graph display; the ZYNQ digital signal processing module integrates FPGA and ARM processor; Design the energy spectrum data processing algorithm in the FPGA part of the ZYNQ chip, including the digital filter shaping module, the pileup rejection module, the baseline estimation module, the amplitude extraction module, and the energy spectrum generation module; The digital filter shaping module is optimized: the analog signal of the γ signal nuclear detector is converted into a digital signal through conditioning, and the continuous time signal is digitized to generate a digital signal represented by discrete time convolution, which is defined as x(n), that is: ； where , and \(0 < a < 1\), \(\Delta T\) is the sampling interval of the ADC. The exponential base \(a\) of the digital exponential signal is related to the decay time constant \(\tau\) of the signal, and the ratio of two consecutive values can be expressed as: ； Where n>0, and x(n)=1, so the deconvolution recursive formula of x(n) can be expressed as: ； Where δ(n) represents the discrete impulse signal; The core of the digital synthesis flat-peak pulse shaping method is to separate and accumulate the corresponding parts of the impulse response after the expansion of x(n) multiple times, and finally synthesize the final peak pulse shape through delay. The time domain expression can be expressed as the following piecewise function: ； in , 、 、 , t a , t b , t c They are the rise time of the peak formation, the sum of the rise time and the flat top time, and the peak formation time; when When , the flat top time is 0; The flat-peak pulse shaping algorithm is a third-order polynomial shaped pulse formed by four consecutive accumulations of the unit pulse δ(n), which is expressed by the following recursive formula: ； ； ； ； The original impulse function x(n) is deconvolved to obtain the impulse signal δ(n), and then δ(n) is synthesized into h through the first accumulation. 3 (n), after the second accumulation, a symmetrical triangular pulse h is synthesized 2 (n), after three accumulations, the bipolar pulse h is obtained 1 (n), and finally the fourth accumulation is performed to obtain the final flat-top peak pulse shape h (n).

2. The portable gamma spectrum measurement system according to claim 1, characterized in that: There is at least one gamma signal detector.

3. The measurement method of the portable gamma spectrum measurement system according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1: Design the hardware structure: Select a high-sensitivity gamma-ray detector unit. Depending on the application requirements, choose a silicon detector or a NaI detector as the sensor for energy spectrum measurement. Select a high-speed ADC for data sampling and a high-performance ZYNQ chip with integrated FPGA and ARM processor for real-time data processing and control. S2: Data acquisition and preprocessing: The gamma-ray signal is converted from the detector into an electrical signal and sent to a fast ADC for high-speed sampling; Afterwards, the collected raw data is preprocessed, including energy scaling and noise filtering; S3: FPGA design; S4: Energy spectrum analysis: After FPGA algorithm optimization, the data is searched for peak positions, the positions of the peaks in the energy spectrum are determined, and the peak areas are calculated. Based on the peak search results, the energy spectrum peaks are integrated, and the energy spectrum peak areas are calculated to reflect the intensity of the radiation source. S5: Result display and storage: The energy spectrum analysis results are displayed in real time on the portable display screen through the display unit for users to view; and the original data and analysis results are stored in the internal memory or external storage medium to facilitate subsequent data playback and further analysis.

4. Application of the measurement method as claimed in claim 3 in nuclear energy and radiation monitoring.

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