Digital double beta-gamma coincidence measurement system

Abstract

The invention relates to a digital double beta-gamma coincidence measurement system, which is characterized by comprising a double beta detector, two gamma detectors and a multi-channel digital spectrometer, the double-beta detector is used for measuring beta rays generated by radioactive gas decay and serves as a to-be-detected gas sample source box, and the gamma detector is used for measuring gamma rays generated by decay; the two gamma detectors are respectively arranged on two sides of the double-beta detector; the multi-channel digital spectrometer is used for respectively providing high voltage for the four detectors, respectively forming, amplifying and collecting signals of the four detectors, and outputting data according to a list mode; the system has the characteristics of high detection efficiency, high resolution, low background and the like, and high-sensitivity measurement of the radioactive gas nuclide activity with cascade decay can be realized.

Description

Technical Field

[0001] The invention belongs to the field of nuclear detection technology and radioactive monitoring technology, and in particular relates to a digital double-β-γ coincidence measurement system, which can be used for high-sensitivity measurement of radioactive gas nuclide activity. Background Art

[0002] Monitoring of radioactive gases in the atmosphere is of great significance for nuclear test ban verification, fissile material production monitoring, and environmental radioactive radiation monitoring, and is an important technical means to maintain national security. The key to monitoring technology lies in the high-sensitivity measurement of atmospheric radioactive activity.

[0003] In order to improve the sensitivity of measuring the activity of radioactive gas nuclides, it is necessary to increase the energy resolution and high detection efficiency of β-rays and γ-rays as much as possible. For example, Sweden, the United States and Russia are conducting research on related technologies of multiple detectors based on PIPS and NaI or high-purity germanium detectors. China currently has β-γ coincidence related technologies, but relatively little research on multiple detectors. Summary of the invention

[0004] The present invention provides a digital dual β-γ coincidence measurement system, which can simultaneously detect β rays and γ rays with high efficiency and high resolution, significantly reduce the environmental radioactive background through β-γ coincidence, and finally realize highly sensitive measurement of the activity of radioactive gas nuclides with cascade decay.

[0005] In order to solve the above technical problems, the present invention provides a digital dual β-γ coincidence measurement system, which is characterized by comprising a dual β detector, two γ detectors, and a multi-channel digital spectrometer; the dual β detector is used to measure the β rays generated by the decay of radioactive gas and serves as a source box for the gas sample to be tested, and the γ detector is used to measure the γ rays generated by the decay; the two γ detectors are respectively placed on both sides of the dual β detector, the gas sample to be tested is filled in the dual β detector, the β rays generated by the decay of the gas sample are measured by the dual β detector, and two signals are output; the γ rays generated by the decay of the gas sample pass through the dual β detector, are measured by the two γ detectors, and two signals are output; the four signals are amplified by independent preamplifiers and respectively input into the multi-channel digital spectrometer, and the digital spectrometer identifies, amplifies, shapes and digitizes each signal.

[0006] Furthermore, the two gamma detectors are two high-purity germanium detectors.

[0007] Furthermore, the digital spectrometer can perform coincidence or anti-coincidence data processing between signals of different channels as required, and output data of all signals in list mode according to the trigger time sequence. The output data includes the trigger time and the amplitude information of each channel signal.

[0008] Furthermore, it also includes a programmable data processing module for processing data online, reading the output data of the multi-channel digital spectrometer in real time, realizing double β signal summation, double γ signal summation, β-γ coincidence operation according to measurement requirements, and saving data.

[0009] Furthermore, the dual-β detector is a sealed structure with a hollow interior, and uses two passivated implanted planar silicon semiconductor detectors to measure β rays.

[0010] Furthermore, the dual β detectors are installed on a bracket, and two ends of the bracket are connected to two γ detectors.

[0011] Furthermore, the multi-channel digital spectrometer includes a high-voltage module, a signal shaping module, a signal amplification module, an analog-to-digital conversion module, and a signal acquisition module;

[0012] The high voltage module is used to provide independent constant DC high voltage for each channel detector according to demand;

[0013] The signal shaping module is used to perform Gaussian or trapezoidal shaping on the output signal of each channel detector;

[0014] The signal amplification module is used to linearly amplify the formed signals of each channel;

[0015] The analog-to-digital conversion module is used to convert the analog signals amplified by each channel into digital signals;

[0016] The signal acquisition module is used for peak finding or integration of digital signals of each channel and outputting data in a list mode.

[0017] Furthermore, the signal acquisition module acquires the trigger time of the event based on the constant ratio timing, acquires the amplitude information of the event based on the peak search or integration, and outputs the data in a list mode to realize the post-processing analysis of the data.

[0018] Further, the programmable data processing module includes an interface module, a data parsing module, and a data processing module;

[0019] The interface module is used to connect to the multi-channel digital spectrometer, send configuration commands, and receive acquisition data;

[0020] The data analysis module is used to read the list mode data output by the multi-channel digital spectrometer in real time;

[0021] The data processing module is used to implement double β signal summation, double γ signal summation, β-γ coincidence operation according to measurement requirements, and save data.

[0022] Furthermore, the multi-channel digital spectrometer is connected to a computer to upload data of the multi-channel digital spectrometer and issue configuration commands.

[0023] Beneficial effects: The present invention can simultaneously detect β-rays and γ-rays with high efficiency and high resolution, significantly reduce the environmental radioactive background through β-γ coincidence, and ultimately achieve highly sensitive measurement of the activity of radioactive gas nuclides with cascade decay.

[0024] 1. The present invention adopts a semiconductor detector based on passivated implanted planar silicon as a beta ray measurement to achieve beta ray energy resolution and detection efficiency; and adopts a double high-purity germanium detector as a gamma ray measurement to achieve gamma ray high energy resolution and high detection efficiency;

[0025] 2. The present invention adopts a multi-channel digital spectrometer to replace the traditional electronic plug-in signal processing system, which greatly simplifies the complexity of the system and improves the system stability. The list mode data ensures the compatibility of the system, and the corresponding programmable data processing program increases the flexibility of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a digital dual β-γ coincidence measurement system according to the present invention;

[0027] Figure 2 Design drawing for the 3D printed detector connection and mounting bracket.

[0028] Figure 3 The PIPS detector measures the internal conversion electron spectrum results of the radioactive 131mXe sample.

[0029] Figure 4 The two-dimensional distribution results of mixed radioactive 131mXe samples measured by the double β-γ coincidence system.

[0030] Among them: 1—the first electrically cooled wide-energy high-purity germanium detector; 2—the second electrically cooled wide-energy high-purity germanium detector; 3—the PIPS detector; 4—the first high-purity germanium detector charge-sensitive preamplifier; 5—the first PIPS detector charge-sensitive preamplifier; 6—the second PIPS detector charge-sensitive preamplifier; 7—the second high-purity germanium detector charge-sensitive preamplifier; 8—the multi-channel digital spectrometer; 9—the computer. DETAILED DESCRIPTION

[0031] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below.

[0032] The present invention proposes a digital dual β-γ coincidence measurement system, comprising a dual β detector, a dual γ detector, a multi-channel digital spectrometer and a programmable data processing module;

[0033] The dual β detector is used to measure the β rays generated by the decay of radioactive gas, and can also be used as a source box for the gas sample to be measured, and has a high β energy resolution;

[0034] The dual γ detector is used to measure the γ rays generated by decay and has a high γ energy resolution;

[0035] The multi-channel digital spectrometer can provide corresponding high voltages according to the requirements of the four detectors;

[0036] The multi-channel digital spectrometer can shape, amplify and collect the four detector signals respectively;

[0037] The multi-channel digital spectrometer can output data of all signals in a list mode according to the trigger time sequence, and the data includes the trigger time and the amplitude information of each channel signal;

[0038] The programmable data processing module is used for online data processing, real-time reading of list mode data output by a multi-channel digital spectrometer, implementation of double β signal summation, double γ signal summation, β-γ coincidence operation according to measurement requirements, and storage of data.

[0039] The dual beta detector is a sealed structure with a hollow interior, using two passivated injected planar silicon (PIPS) semiconductor detectors, a stainless steel bracket and carbon fiber materials to form an internal hollow sealed structure, with a lemo output interface and a 1 / 16 inch gas pipeline interface on the outside, which is conducive to improving the beta ray energy resolution.

[0040] The dual γ detectors are two wide-energy high-purity germanium detectors based on electric cooling. The two high-purity germanium detectors are placed opposite to each other and are respectively placed on both sides of the dual β detector to form a solid angle of nearly 4π.

[0041] The dual β detector is installed on a 3D printed bracket, and the two ends of the bracket are connected to two high-purity germanium detectors. The entire system has a compact structure, which is conducive to improving the efficiency of γ-ray detection.

[0042] The multi-channel digital spectrometer includes a high-voltage module, a signal shaping module, a signal amplification module, an analog-to-digital conversion module, and a signal acquisition module;

[0043] The high-voltage module is used to provide independent constant-stable DC high voltage for each channel detector according to demand; a DC-DC conversion method is used to achieve an output voltage of 0 to ±5000V, and a digital DAC is used to achieve high-voltage rise and fall adjustment and digital control settings.

[0044] The signal shaping module is used to perform Gaussian or trapezoidal shaping on the output signals of the detectors of each channel; the design of fast and slow shaping channels based on symmetrical zero area reduces the error caused by low-frequency fluctuations during the traditional trapezoidal forming amplitude extraction, suppresses low-frequency noise, and is conducive to improving the resolution of low-energy signals.

[0045] The signal amplification module is used to linearly amplify the formed signals of each channel;

[0046] The analog-to-digital conversion module is used to convert the analog signals amplified by each channel into digital signals, with a sampling rate of 80MHz; the use of the AD9266-80 high-speed ADC chip is beneficial to reducing the system dead time and improving the system's compatibility with different types of detectors;

[0047] The signal acquisition module is used for peak search or integration of digital signals of each channel, and outputs data in list mode. The signal acquisition module collects information such as the trigger time of the event based on constant ratio timing, the amplitude of the event based on peak search or integration, and outputs data in list mode to achieve post-processing analysis of the data.

[0048] The programmable data processing module includes an interface module, a data analysis module, and a data processing module;

[0049] The interface module is used to connect to the multi-channel digital spectrometer, send configuration commands, and receive acquisition data;

[0050] The data analysis module is used to read the list mode data output by the multi-channel digital spectrometer in real time;

[0051] The data processing module is used to implement operations such as dual β signal summation, dual γ signal summation, β-γ coincidence, etc. according to measurement requirements, and save data.

[0052] Specifically, the dual-β detector uses the PIPS detector produced by Canberra, which is based on two pieces of passivated injected planar silicon, with a stainless steel bracket and carbon fiber material forming an internal hollow sealed structure. The silicon thickness is 500μm, the carbon fiber window thickness is less than 50μm, the sensitive area is 1200mm2, and the internal volume of the detector is 10.6cm3.

[0053] PIPS uses a lemo interface to connect to a charge-sensitive preamplifier, which is responsible for both power supply and signal transmission. The preamplifier connects two cables to a multi-channel digital spectrometer, one cable for high voltage supply and one cable for signal transmission. There is a 1 / 16-inch gas line on the PIPS detector, which is combined with a laboratory vacuum pump to charge and extract the sample to be tested.

[0054] The dual gamma detector uses the BE5030P detector produced by Canberra, which is a wide-energy, high-purity germanium detector based on electrical cooling. The signal outputs are connected to charge-sensitive preamplifiers, and then connected to a multi-channel digital spectrometer via two cables, one for high-voltage supply and the other for signal transmission.

[0055] The dual β detectors are installed on a bracket, which is made of 3D printed polymer materials to reduce the radioactive background. The two high-purity germanium detectors are placed opposite each other, and the two ends of the bracket are fixed on the surface of the two high-purity germanium detectors. The bracket structure is as follows: Figure 2 As shown; the entire system is compact and forms a solid angle close to 4π.

[0056] The multi-channel digital spectrometer is connected to the computer via a Gigabit Ethernet communication interface to upload data of the multi-channel digital spectrometer and issue configuration commands.

[0057] A programmable data processing module is deployed on the computer, which adopts a distributed design and uses interface operation to perform flexible configurations such as double β signal summation, double γ signal summation, and β-γ coincidence, thus realizing online real-time processing of measurement data.

[0058] by Figure 1 For example, the present invention is used for high-sensitivity measurement of radioactive gases.

[0059] The PIPS detector has a PIPS on each of the upper and lower sides, which together with the surrounding structural parts form a closed detector. There is a chamber inside the detector, and the gas sample to be tested is filled into the chamber. The β rays generated by the decay of the gas sample are measured by the PIPS on both sides, and the γ rays generated by the decay of the sample pass through the PIPS detector and are measured by two high-purity germanium detectors. The signals of the PIPS detector and the high-purity germanium detector are amplified by independent preamplifiers and then input into a four-channel digital spectrometer. The digital spectrometer identifies, amplifies, shapes and digitizes each signal separately. The data output by the spectrometer can be saved in list mode for offline processing, and the coincidence or anti-coincidence data processing between signals of different channels can be performed according to the needs, such as (PIPS-1||PIPS-2)&(HPGe-1||HPGe-2). This system uses two β and two γ detectors respectively, which have high detection efficiency for both β and γ rays. At the same time, the background count rate of the system is reduced by coincidence, and finally a high-sensitivity measurement of the radioactivity of the gas sample is achieved.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A digital dual β-γ coincidence measurement system, characterized in that: It includes dual β detectors, two γ detectors, and a multi-channel digital spectrometer; The dual-β detector is used to measure the β rays generated by the decay of radioactive gas and serves as a source box for the gas sample to be tested. The γ detector is used to measure the γ rays generated by the decay. The two γ detectors are respectively placed on both sides of the dual-β detector. The gas sample to be tested is filled in the dual-β detector. The β rays generated by the decay of the gas sample are measured by the dual-β detector and two signals are output. The γ rays generated by the decay of the gas sample pass through the dual-β detector and are measured by the two γ detectors and two signals are output. The four signals are amplified by independent preamplifiers and respectively input into a multi-channel digital spectrometer. The digital spectrometer identifies, amplifies, shapes and digitizes each signal.

2. A digital dual β-γ coincidence measurement system according to claim 1, characterized in that: The two gamma detectors are two high-purity germanium detectors.

3. A digital dual β-γ coincidence measurement system according to claim 1, characterized in that: The digital spectrometer can process coincidence or anti-coincidence data between signals of different channels according to requirements, and output data of all signals in list mode according to the trigger time sequence. The output data includes the trigger time and the amplitude information of each channel signal.

4. A digital dual β-γ coincidence measurement system according to claim 1, characterized in that: It also includes a programmable data processing module for processing data online, reading the output data of the multi-channel digital spectrometer in real time, realizing double β signal summation, double γ signal summation, β-γ coincidence operation according to measurement requirements, and saving data.

5. A digital dual β-γ coincidence measurement system according to claim 1, characterized in that: The double beta detector is a sealed structure with a hollow interior, and uses two passivated implanted planar silicon semiconductor detectors to measure beta rays.

6. A digital dual β-γ coincidence measurement system according to claim 1, characterized in that: The double β detectors are installed on a bracket, and two ends of the bracket are connected to two γ detectors.

7. A digital dual β-γ coincidence measurement system according to any one of claims 1 to 6, characterized in that: The multi-channel digital spectrometer includes a high-voltage module, a signal shaping module, a signal amplification module, an analog-to-digital conversion module, and a signal acquisition module; The high voltage module is used to provide independent constant DC high voltage for each channel detector according to demand; The signal shaping module is used to perform Gaussian or trapezoidal shaping on the output signal of each channel detector; The signal amplification module is used to linearly amplify the formed signals of each channel; The analog-to-digital conversion module is used to convert the analog signals amplified by each channel into digital signals; The signal acquisition module is used for peak finding or integration of digital signals of each channel and outputting data in a list mode.

8. A digital dual β-γ coincidence measurement system according to claim 7, characterized in that: The signal acquisition module collects the trigger time of the event based on constant ratio timing, the amplitude information of the event based on peak finding or integration, and outputs the data in list mode to achieve post-processing and analysis of the data.

9. A digital dual β-γ coincidence measurement system according to claim 4, characterized in that: The programmable data processing module includes an interface module, a data analysis module, and a data processing module; The interface module is used to connect to the multi-channel digital spectrometer, send configuration commands, and receive acquisition data; The data analysis module is used to read the list mode data output by the multi-channel digital spectrometer in real time; The data processing module is used to implement double β signal summation, double γ signal summation, β-γ coincidence operation according to measurement requirements, and save data.

10. The digital dual β-γ coincidence measurement system according to claim 1, characterized in that: The multi-channel digital spectrometer is connected to a computer to upload data of the multi-channel digital spectrometer and issue configuration commands.

Images