Portable gamma energy spectrum measuring system and method thereof

Abstract

The invention discloses a portable gamma energy spectrum measuring system which comprises 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 with the gamma signal detector and the ADC digital acquisition circuit; the ADC digital acquisition circuit is connected with the ZYNQ digital signal processing module, and is finally connected with the display module for map display; according to the method, a flat-top expandable peak forming method provided by a recursive equation is introduced, an input negative index signal is firstly subjected to deconvolution expansion to form a pulse signal, the pulse signal is synthesized into a peak flat-top shape through convolution, and accurate extraction of the peak value of the negative index signal is realized. According to the system, the FPGA and the ARM processor are integrated by adopting the ZYNQ chip, so that the miniaturization of hardware is realized, and the whole system is small in size, light in weight and convenient 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] As people pay more and more attention to radiation safety, radiation can cause serious effects such as cancer and genetic mutations. Among radiation, gamma rays have the most serious penetrating properties. Therefore, it is very important to measure the gamma spectrum. The gamma spectrum measurement can provide key information for material structure research, radionuclide identification, nuclear reaction analysis, material composition analysis, and radiation dose assessment. Existing gamma spectrum measurement systems mainly include traditional desktop instruments and portable devices. Traditional desktop instruments usually have high performance and accuracy, but due to their large size and complex operation, they are not easy to carry and measure in real time, which limits their application range. On the other hand, although existing portable gamma spectrum measurement instruments are easy to carry, they usually have low sensitivity and poor spectral resolution due to technical limitations, and cannot meet the needs of accurate monitoring and analysis of radiation sources.

[0003] In summary, the existing portable γ-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 difficult to effectively improve the energy spectrum resolution, which makes it difficult to clearly distinguish the energy peaks in the energy spectrum, affecting the accurate identification and analysis of radiation sources.

[0006] 3. Complex data processing: In the existing technology, the data processing process is relatively complicated 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 will increase energy consumption, resulting in limited device usage time. Summary of the invention

[0008] The purpose of the present invention is to realize a flat-top peak filtering shaping algorithm on a ZYNQ-7000 series platform integrating FPGA and ARM processor. The 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 a recursive equation, fast digital signal processing can be performed on FPGA to achieve efficient and real-time system. At the same time, since the ZYNQ chip and other devices used are highly integrated, they can be portable. Through the 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 γ spectrum measurement system, including: a γ 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 γ 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 processors; 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 γ signal nuclear detector is converted into a digital signal through conditioning, the continuous time signal is digitized, and the digital signal represented by the discrete time convolution is generated and 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 continuous 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 shock discrete signal;

[0016] The core of the digital synthesis flat-top peak pulse shaping method is to separate and accumulate the corresponding parts of the impulse response after x(n) expansion for 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 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 n a -n b =0, the flat top time is 0;

[0019] The flat peak pulse shaping algorithm of the third-order polynomial shaping obtained 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 pulse function x(n) is deconvolved to obtain the impulse signal δ(n), and then δ(n) is synthesized by the first accumulation to form h 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] Further, the gamma signal detector is at least one;

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

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

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

[0029] S3: FPGA design;

[0030] S4: Energy spectrum analysis: After being optimized by the FPGA algorithm, the data is searched for peak positions, the positions of each peak in the energy spectrum are determined, and the peak areas are calculated: according to the peak search results, the peak positions of the energy spectrum are integrated, and the peak areas of the energy spectrum 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 beneficial effects of the present invention are as follows: the present invention introduces a flat-top expandable peak shaping method proposed by a recursive equation, first deconvolves the input negative exponential signal into a pulse signal, and synthesizes it into a peak flat-top shape through convolution, thereby realizing accurate extraction of the peak value of the negative exponential signal. The system uses ZYNQ chip to integrate FPGA and ARM processor, realizing the miniaturization of hardware, making the entire system small in size, light in weight, easy to carry and operate. The high-performance computing capability of FPGA and the fast response capability of ARM processor enable the system to collect and analyze gamma-ray energy spectrum data in real time; the system is suitable for the fields of nuclear energy, environmental protection, etc., and has broad application prospects in nuclear power plants, radiation monitoring stations and other places. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0034] Figure 1 This is a structural block diagram of a portable γ-ray spectrum measurement system;

[0035] Figure 2 This is a transfer function model for sharp pulse shaping in a portable gamma spectrum measurement system.

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

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

[0038] Example 1

[0039] In this embodiment, the scintillator detector 137Cs energy spectrum experimental measurement is performed. When performing the experiment, a NaI (Tl) scintillator detector is selected and placed 10 cm away from the center of the top of the detector. 137 Cs radiation source measurement, the measurement time is 10 minutes; and multiple measurements are performed to obtain 137 The energy spectrum measurement results of Cs, taking the channel address corresponding to the characteristic peak as the test object of system stability, test the stability of the system. The results are shown in Table 1. The total number of system channels is 4096, and the average channel address in 9 tests is 2548, with only 10 channel addresses deviation, indicating that the system has good stability;

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

[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 a flat-top peak pulse shaping system based on the expansion-synthesis technique is described in the text. The detector analog signal is usually conditioned and applied to a digital ADC to be converted into a discrete time signal; the process of digital pulse shaping is achieved by first expanding (deconvolving) the digitized analog signal and then achieving it by synthesizing the pulse response of the desired pulse shape.

[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 As shown in the results, 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 higher counting rate passability than the other three algorithms; considering both the energy resolution and counting rate passability, the flat top peak pulse shaping algorithm exhibits better performance.

[0046] The specific use principle of the present invention is: first, turn on the system power supply, start the system, and enter the standby state after the system initialization is completed; then aim the gamma signal detector 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, and can also 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 supply to complete the measurement process.

[0047] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the 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 the 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 spectrum display; the ZYNQ digital signal processing module integrates FPGA and ARM processor; In the FPGA part of the ZYNQ chip, the energy spectrum data processing algorithm is designed, which mainly includes digital filter shaping module, pile-up rejection module, baseline estimation module, amplitude extraction module, energy spectrum generation module and other functional modules; The digital filter shaping module is optimized: the analog signal of the γ signal nuclear detector is converted into a digital signal after adjustment, 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 a = e -ΔT / τ , and 0 < a < 1, ΔT is the sampling interval of the 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: Where n>0, and x(n)=1, so the deconvolution recursive formula of x(n) can be expressed as: x(n)=δ(n)+ax(n-1) Where δ(n) represents the shock discrete signal; The core of the digital synthesis flat-top peak pulse shaping method is to separate and accumulate the corresponding parts of the impulse response after x(n) expansion for multiple times, and finally synthesize the final peak pulse shape through delay. The time domain expression can be expressed as the following piecewise function: 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 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 n a -n b =0, the flat top time is 0; The flat peak pulse shaping algorithm of the third-order polynomial shaping obtained by four consecutive accumulations of the unit pulse δ(n) can be expressed by the following recursive formula: h 3 (n)=h 3 (n-1)+δ(n)-δ(nn a )-δ(nn b -2)+δ(nn c -2) h 2 (n)=h 2 (n-1)+h 3 (n)-n a [δ(nn a )-δ(nn b -1)] h(n)=h(n-1)+h 1 (n) The original pulse function x(n) is deconvolved to obtain the impulse signal δ(n), and then δ(n) is synthesized by the first accumulation to form h 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. A 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 γ-ray detector unit. According to the application requirements, select silicon detectors or NaI detectors as sensors for energy spectrum measurement; select high-speed ADC for data sampling to improve the frequency and accuracy of data acquisition. At the same time, select high-performance ZYNQ chips, integrate FPGA and ARM processors, for real-time data processing and control; S2: Data acquisition and preprocessing: The gamma-ray signal is converted into an electrical signal by the detector and sent to a fast ADC for high-speed sampling; the collected raw data is then preprocessed, including energy calibration, noise filtering, etc., to improve the accuracy of subsequent data analysis; S3: FPGA design; S4: Energy spectrum analysis: After being optimized by the FPGA algorithm, the data is searched for peak positions, the positions of each peak in the energy spectrum are determined, and the peak areas are calculated: according to the peak search results, the peak positions of the energy spectrum are integrated, and the peak areas of the energy spectrum 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 of the portable gamma spectrum measurement system as claimed in claim 3 in nuclear energy and radiation monitoring.

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