CN117687072A - Coincidence detection equipment for radioactivity measurement and application thereof - Google Patents

Abstract

The invention discloses coincidence detection equipment for radioactivity measurement, which comprises a frame, a detector arranged on the frame and an air inlet and outlet interface; a gas measurement chamber is arranged in the frame; the frame is a semi-regular polyhedron and comprises a triangular surface and a square surface, and the detector is arranged on the square surface; the detector is a tellurium-zinc-cadmium detector. The detection equipment is particularly suitable for radioactive measurement of radioactive xenon, and solves the defects that a high-purity germanium gamma spectrometer and a NaI+plastic scintillator beta-gamma coincidence detector are large in size, heavy and difficult to maintain, and are difficult to realize portability, in-situ measurement and the like; the lower detection limit can be achieved, and the measuring precision is higher than that of a NaI detector; the appearance of the detector adopts a semi-regular polyhedron design, so that the spatial symmetry of each detector is ensured, and the larger 4 pi coverage rate of the detector is obtained; the volume of the measuring cavity is increased, the requirement on air separation and concentration is reduced, and the problem that the traditional beta-gamma coincidence detector is limited in measuring cavity is solved.

Description

Coincidence detection equipment for radioactivity measurement and application thereof

Technical Field

The invention belongs to the technical field of radioactive detectors, relates to measurement of radioactive inert gas xenon, and particularly relates to a semi-regular polyhedron tellurium-zinc-cadmium coincidence detection device for radioactive measurement and application of the coincidence detection device in radioactive inert gas, particularly xenon radioactive measurement.

Background

The radioactive inert gas xenon is an important nuclide in radioactive gas-carrying effluent which may be discharged into the environment by nuclear facilities, and related standards in China require periodic sampling monitoring or continuous measurement of xenon radioactivity in stack exhaust gas during the operation of nuclear facilities such as nuclear power plants, nuclear post-treatment plants and the like. In addition, the inert gas fission products generated in the nuclear explosion process are easy to leak into the atmosphere, and the measurement result of radioactive xenon in the air is completely prohibited by a nuclear test treaty (CTBT) International Monitoring System (IMS) as one of four technologies for checking and identifying suspicious nuclear explosion.

The nuclides to be monitored with emphasis in the radioactive xenon isotopes are Xe-131m, xe-133m and Xe135, considering factors such as the size of the fission yield and the length of the half-life.

At present, the domestic measurement of xenon radioactivity is mainly carried out by a gamma energy spectrum measurement method, namely, the gas carrying effluent is sampled in a 3L steel cylinder, and then the measurement is carried out by a high-purity germanium gamma spectrometer. The method has the following defects:

1) The emission probability of the gamma rays of the xenon radioactive isotopes Xe-131m and Xe-133m is low (1.95% and 10% respectively), so that the detection limit of a gamma energy spectrum measuring method is high;

2) The high-purity germanium detector works in a liquid nitrogen low-temperature environment under laboratory conditions, and is high in maintenance cost and difficult to realize on-site measurement.

Compared with a gamma energy spectrum measuring method, the beta-gamma coincidence measuring method can effectively reduce background influence of environmental radioactivity, and meanwhile, according to decay characteristics of xenon radioactive isotopes, the coincidence measurement is carried out by adopting X rays with higher emission probability, so that a lower detection limit can be achieved. According to the requirement of CTBT on measurement detection limit of xenon in air, a beta-gamma coincidence detection system (such as SAUNA system developed by Switzerland, ARSA developed by America and the like) based on a NaI scintillator and a plastic scintillator is developed abroad, and gamma rays are measured by the method through a NaI scintillator detector, and beta rays are measured by the plastic scintillator, so that beta-gamma coincidence measurement is realized. The main disadvantages of this type of measurement system are:

1) The NaI scintillator detector has low energy resolution, and large environmental nuclide interference, so that the statistical error of the measurement result is large;

2) The gas chamber is positioned in the plastic scintillator, the plastic scintillator is positioned in the NaI crystal, the volume of the gas chamber is smaller due to the shadow of the size of the NaI crystal, and the high requirement on separation and concentration of xenon is met;

3) Signals of the NaI detector and the plastic scintillator detector are read out through a photomultiplier, so that the whole system is huge in size, and meanwhile, the NaI detector and the plastic scintillator detector are sensitive to environment gamma radiation, and in order to reduce background shadows, the system is usually required to be provided with a lead shielding system with huge size.

Disclosure of Invention

In view of the above, in order to overcome the defects of the prior art, the invention aims to provide a semi-regular polyhedron tellurium-zinc-cadmium coincidence detection device suitable for xenon radioactivity measurement.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the semi-regular polyhedron tellurium-zinc-cadmium coincidence detection equipment suitable for xenon radioactivity measurement comprises a frame, a detector arranged on the frame and an air inlet and outlet interface; a gas measurement chamber is arranged in the frame; the frame is a semi-regular polyhedron and comprises a triangular surface and a square surface, and the detector is arranged on the square surface; the detector is a tellurium-zinc-cadmium detector.

According to some preferred embodiments of the invention, the semi-regular polyhedron is a small rhombic truncated semi-cube, consisting of 18 square faces and 8 regular triangular rows.

According to some preferred embodiments of the invention, the semi-regular polyhedron is a truncated cube, consisting of 6 square faces and 8 regular triangle faces.

According to some preferred embodiments of the invention, the normal direction of the crystal detection face of the tellurium-zinc-cadmium detector is directed toward the center of the gas measurement chamber.

According to some preferred embodiments of the invention, each of the tellurium-zinc-cadmium detectors on the frame has an equivalent geometric position and the same detection efficiency for the gas in the measurement chamber. Namely, the inside of the semi-regular polyhedron detector frame forms a space-symmetrical semi-regular polyhedron gas measuring chamber. And tellurium-zinc-cadmium detectors arranged on the square surface of the semi-regular polyhedron form a space symmetrical layout for the gas measuring chamber, and each tellurium-zinc-cadmium detector has equivalent geometric positions and the same detection efficiency for the gas of the measuring chamber.

According to some preferred embodiments of the present invention, there is provided a test source needle holder interface and a test source needle holder mounted on the test source needle holder interface; the air inlet and outlet interface and the test source needle frame interface are arranged on the triangular surface; the test source probe rack is used for testing the performance of the detector. Namely, the square surface is used for installing the tellurium-zinc-cadmium detector, and the triangular surface is mainly used for installing the air inlet and outlet interfaces and the test source needle frame interface. The test source needle frame is used for detecting main performance parameters and stability of the detector. The adopted test source needle frame design solves the problem that the gas detector is not easy to develop performance test.

According to some preferred embodiments of the invention, the test source needle holder comprises a needle holder cap, a sealing ring, a needle holder rod and a radioactive point source in this order, the needle holder rod being mounted in the test source needle holder interface such that the radioactive point source is located in the gas measurement chamber.

According to some preferred embodiments of the invention, the radioactive point source comprises 3 types: radiation sources having beta-gamma coincidence decay, gamma radiation sources, and beta radiation sources.

According to some preferred embodiments of the invention, the cover is provided with a preformed hole for leading out the signal line and the power line of the detector.

According to some preferred embodiments of the present invention, a signal processing system is included that includes a detector power module, a multi-channel preamplifier, a multi-channel high speed ADC, a filtering module, a peak acquisition module, a coincidence signal identification module, and a data storage and transmission module. The signal processing system is a beta-gamma coincidence signal processing system based on an FPGA.

According to some preferred embodiments of the invention, the detector power supply module is configured to provide an operating power supply to the tellurium-zinc-cadmium detector; the multichannel preamplifier is used for amplifying pulse signals output by the tellurium-zinc-cadmium detector; the multi-channel high-speed ADC is used for collecting pulse shape data and digitizing pulse waveforms; pulse shape data refers to converting a continuous analog voltage pulse signal into discrete voltage values.

The coincidence signal identification module is used for real-time screening of output signals of the multipath pre-amplifier, and when any two paths of signals generate pulse signals in a given coincidence time window, trigger signals and coincidence signal channel numbers are respectively sent to the filtering module and the peak value acquisition module; the filtering module immediately acquires pulse waveform data corresponding to the channel number output by the multi-channel high-speed ADC after receiving the trigger signal, and the peak value acquisition module acquires a peak value in the waveform data and sends the peak value and the channel number to the data storage and transmission module; and the data storage and transmission module transmits the measurement result information to the upper computer according to a certain frequency. The coincidence signal identification module, the filtering module, the peak value acquisition module and the data storage and transmission module are realized by adopting a programmable gate array (FPGA).

According to some preferred embodiments of the invention, the coincidence time window is set to be within ten ns for the difference between the arrival of the coincident two signals at the coincidence signal identification module.

According to some preferred embodiments of the present invention, the channel number corresponds to the number of two tellurium-zinc-cadmium detectors generating a coincidence signal, the peak, i.e., the peak of the voltage pulse output by the detector, representing the energy of the radiation decaying from the radioactive source.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages: the semi-regular polyhedron tellurium-zinc-cadmium coincidence detection equipment suitable for xenon radioactivity measurement solves the defects that a high-purity germanium gamma spectrometer and a NaI+plastic scintillator beta-gamma coincidence detector are large in size, heavy in weight, difficult to maintain, difficult to realize portability, in-situ measurement and the like; the beta-gamma coincidence measurement technology realized by adopting the tellurium-zinc-cadmium detector can reach lower detection limit compared with a high-purity germanium detector, and has higher measurement precision compared with a NaI detector; the appearance of the detector adopts a semi-regular polyhedron design, so that the spatial symmetry of each detector is ensured, and the larger 4 pi coverage rate of the detector is obtained; the semi-regular polyhedron detector is adopted for appearance design, so that the volume of a measuring cavity can be increased, the requirement on air separation and concentration is reduced, and the problem that the traditional beta-gamma coincidence detector is limited in measuring cavity is solved; the problem that the air inlet and outlet of the gas measuring chamber are arranged to influence the symmetry is solved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a frame structure of a coincidence detecting apparatus in a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram of a frame structure of a coincidence detecting apparatus in accordance with another preferred embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a detector of a coincidence detecting apparatus in accordance with a preferred embodiment of the present invention;

FIG. 4 is a schematic diagram of a test source needle holder according to a preferred embodiment of the present invention;

FIG. 5 is a schematic diagram of a system for processing a beta-gamma coincidence signal of a coincidence detecting apparatus in accordance with a preferred embodiment of the present invention;

in the drawing, 10, a small oblique-square-section half-cube detector frame; 11. an air inlet and outlet interface of the air measuring chamber; 12. a semi-regular polyhedron square face; 13. a tellurium-zinc-cadmium detector accommodating groove; 14. regular polyhedron regular triangle surface; 15. a test source needle holder interface; 16. a semi-regular polyhedron detector frame connecting rib; 17. a truncated cube detector frame;

20. a cross-sectional view of a semi-regular polyhedron detector; 21. the outer cover of the detector is provided with a preformed hole; 22. the outer cover of the detector is fixed with a screw; 23. a detector outer cover; 24. a frame clamping part; 25. cadmium zinc telluride detector; 26. a tellurium-zinc-cadmium crystal detection surface; 27. a gas measurement chamber; 30. a test source needle holder; 31. needle frame cap; 32. a seal ring; 33. a needle rack rod; 34. a radioactive point source;

40. beta-gamma accords with a signal processing system based on FPGA; 41. a detector power module; 42. a multi-way preamplifier; 43. a multi-way high speed ADC; 44. a filtering module; 45. a peak value acquisition module; 46. a coincidence signal identification module; 47. and a data storage and transmission module.

Detailed Description

In order to make the technical solution of the present invention better understood by those skilled in the art, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

As shown in fig. 1-5, the semi-regular polyhedron tellurium-zinc-cadmium coincidence detection device suitable for xenon radioactivity measurement in the embodiment comprises two parts of a spatially symmetrical beta-gamma coincidence detector formed by semi-regular polyhedron detector frames 10 and 17 and a tellurium-zinc-cadmium detector 25 and a beta-gamma coincidence signal processing system 40 based on an FPGA. The semi-regular polyhedron detector frame is of two types, small rhombic truncated half-cube detector frame 10 or truncated half-cube detector frame 17. The tellurium-zinc-cadmium detector 25 is mounted on the square face of the semi-regular polyhedron detector frame 10, 17 to form a detector group capable of carrying out beta-gamma coincidence measurement on radioactive gas in the frame. The core modules of the FPGA-based β - γ coincidence signal processing system 40 are a coincidence signal identification module 46 and a peak acquisition module 45. The following describes the specific structure of the detection device:

spatially symmetric beta-gamma coincidence detector

As shown in fig. 1-4, the β - γ coincidence detector in this embodiment includes a frame 10 or 17, a cadmium zinc telluride detector 25 disposed on the frame 10 or 17, an air inlet and outlet interface 11, a test source needle holder interface 15, and a test source needle holder 30 mounted on the test source needle holder interface 15.

The frame 10 or 17 has a gas measurement chamber 27 therein; the frame 10 or 17 is made of aluminum alloy material and is in a semi-regular polyhedron shape, and comprises a triangular surface 14 and a square surface 12, and a frame connecting rib 16 is arranged at the joint between the triangular surface 14 and the square surface 12. The tellurium-zinc-cadmium detector 25 is arranged on the square surface 12, and the air inlet and outlet interface 11 and the test source needle frame interface 15 are arranged on the triangular surface 14. The semi-regular polyhedron frame 10 or 17 is sealed with the detector 25, the air inlet and outlet 11 and the test source needle frame mounting port 15 by adopting rubber sealing rings, so that the whole measuring gas chamber is sealed and isolated from the outside.

The test source probe holder 30 is used for testing the performance of the coincidence detector, and mainly comprises: the beta detection efficiency, the gamma detection efficiency and the coincidence detection efficiency of the total detector of each tellurium-zinc detector 25 can be tracked by the total counting rate (measurement result in unit time of the detector) of each detector. When the stability test of the detector is required, the required radioactive point source 34 is arranged at the top end of the needle frame rod, then the test source needle frame 30 is inserted, and different indexes of the instrument can be tested by adopting different radioactive point sources 34. The instrument test and the sample measurement are independently completed, so that the problem that the performance test of the gas detector is difficult to develop is solved.

Specifically, as shown in FIG. 4, the test source needle holder includes, in order, a needle cap 31, a seal ring 32, and a needle holder rod 33 and a radioactive point source 34, the needle holder rod 33 extending through the test source needle holder interface 15 such that the radioactive point source 34 is positioned within the gas measurement chamber 27. The radioactive point source 34 comprises 3 types: radiation sources such as Cs-137, co-60 and the like which are easy to obtain and have beta-gamma consistent decay; taking the molded Am-241 as a gamma radiation source; and Sr/Y-90 and other beta radioactive sources. The point source can be prepared by adopting standard solution drying. The sealing ring is in threaded sealing connection with the test source needle frame interface.

When the performance and stability test of the instrument is required to be carried out, the test source needle frame 30 is taken out, the required radioactive point source 34 is arranged at the top end of the needle frame rod, then the test source needle frame 30 is reinserted, and different indexes of the instrument can be tested by adopting different radioactive point sources 34.

As shown in fig. 1, the half regular polyhedron of the frame 10 in this embodiment is a small rhombic half cube, and is formed by 18 square faces 12 and 8 regular triangular faces 14. In other embodiments, the half-regular polyhedron of the frame 17 is a truncated half-cube, consisting of 6 square faces 12 and 8 regular triangular faces 14, as shown in fig. 2. The square surface 12 of the two types of semi-regular polyhedron frames is used for installing tellurium-zinc-cadmium detectors 25, and the triangular surface is mainly used for installing the air inlet and outlet interfaces 11 and the test source needle frame interface 15; the square surfaces are all provided with tellurium-zinc-cadmium detectors 25.

For both applications of xenon radioactivity measurement in a typical environment and xenon in the gaseous effluent of a nuclear facility, a small rhombic half-cube detector frame 10 with a large number of detectors and a half-cube detector frame 17 with a small number of detectors can be selected, respectively. According to the requirements of the current front-end gas concentration treatment technology and related standard specifications on measurement and detection, the model and the frame size of the detector are designed as follows:

as shown in fig. 1, the small rhombic half cube detector frame 10 is cast from aluminum alloy or integrally. The tellurium-zinc-cadmium detector is a hemispherical tellurium-zinc-cadmium detector with the model of 10mm (length) ×10mm (width) ×5mm (thickness), 18 detectors are arranged on 18 square surfaces of a small rhombic half-cube detector frame, and the size of an inner cavity of the small rhombic half-cube detector frame is set as follows: the side length of the regular quadrangle is 1.2cm (the side length of the regular triangle is the same as that of the regular quadrangle). Can obtain the gas of the small rhombic half-cube detectorThe measurement chamber volume was 15.1cm ³ The 4pi coverage of 18 detectors was 58.2%.

As shown in fig. 2, the half-cube detector frame 17 is integrally cast from aluminum alloy, and the tellurium-zinc-cadmium detector is a hemispherical tellurium-zinc-cadmium detector with the model of 10mm (length) ×10mm (width) ×5mm (thickness), 6 detectors are mounted on 6 square surfaces of the small oblique half-cube detector frame, and the size of the inner cavity of the half-cube detector frame is set as follows: the side length of the regular quadrangle is 2.0cm (the side length of the regular triangle is the same as that of the regular quadrangle). The volume of the gas measuring cavity of the small rhombic half-cube detector can be 8.0cm ³ The 4pi coverage of 18 detectors was 25.1%.

As shown in fig. 3, the normal direction of the crystal detection face 26 of the cadmium zinc telluride detector 25 is directed toward the center of the gas measurement chamber 27. The interior of the semi-regular polyhedron detector frame forms a spatially symmetric semi-regular polyhedron gas measurement chamber 27. The tellurium-zinc-cadmium detectors 25 arranged on the regular polyhedron square surface 12 form a space symmetrical layout for the gas measuring chamber 27, and each tellurium-zinc-cadmium detector has equivalent geometric positions and the same detection efficiency for the gas of the measuring chamber, so that the processing method for the detector availability and the rear-end multipath beta-gamma coincidence signals can be simplified.

As shown in fig. 3, a clamping part 24 is arranged on one side of the square surface 12 close to the gas measuring chamber 27, and an outer cover 23 is arranged on one side away from the gas measuring chamber; an accommodating groove 13 for accommodating the tellurium-zinc-cadmium detector 25 is formed between the clamping part 24 and the outer cover 23. The cover 23 is provided with a preformed hole 21 for leading out the signal line and the power line of the detector. The joint of the detector outer cover 23, the tellurium-zinc-cadmium detector 25 and the semi-regular polyhedron detector frame is provided with a rubber gasket, so that the purpose of sealing the measuring cavity is achieved.

During installation, the tellurium-zinc-cadmium detector 25 is inserted into the accommodating groove 13 from outside to inside, and the outer surface of the tellurium-zinc-cadmium detector is fixed through the outer detector cover 23; the detector cover 23 is secured to the semi-regular polyhedron detector frame by screws 22.

(II) beta-gamma coincidence signal processing system based on FPGA

As shown in fig. 5, the β - γ coincidence signal processing system 40 in this embodiment includes a detector power module 41, a multi-channel preamplifier 42, a multi-channel high-speed ADC43, a filtering module 44, a peak acquisition module 45, a coincidence signal identification module 46, and a data storage and transmission module 47.

The detector power supply module 41 is used for uniformly providing working power supply for the tellurium-zinc-cadmium detector 25; the multi-channel preamplifier 42 is used for amplifying the pulse signals output by the tellurium-zinc-cadmium detector; the multi-channel high-speed ADC43 is used for collecting pulse shape data and digitizing the pulse waveform. Pulse shape data refers to converting a continuous analog voltage pulse signal into discrete voltage values.

The coincidence signal identification module 46, the filtering module 44, the peak acquisition module 45, and the data storage and transmission module 47 are implemented using a programmable gate array (FPGA). The coincidence signal identifying module 46 is configured to discriminate the output signals of the multiple preamplifiers in real time, and when any two signals generate pulse signals within a given coincidence time window, send trigger signals and coincidence signal channel numbers to the filtering module 44 and the peak value obtaining module 45.

The coincidence time window is the possible difference between the arrival of the coincident two signals at the coincidence signal identification module 46, typically set in the tens of ns range, typically determined experimentally.

After the filtering module 44 receives the trigger signal, pulse waveform data corresponding to the channel number output by the multi-channel high-speed ADC43 is immediately acquired, and the peak value acquiring module 45 acquires a peak value in the waveform data and sends the peak value and the channel number to the data storing and transmitting module 47; the data storage and transmission module 47 transmits the measurement result information to the upper computer according to a certain frequency.

The channel numbers correspond to the numbers of the two tellurium-zinc-cadmium detectors which generate the coincidence signals; the peak, i.e., the peak of the voltage pulse output by the detector, represents the energy of the radiation decaying from the radiation source.

The numerical value storage is realized by adopting a built-in data buffer FIFO (Internet protocol) in the FPGA, and the data transmission mode can be applicable to a serial port protocol or a USB homography protocol.

The beta-gamma coincidence signal processing system based on the FPGA adopts the coincidence signal identification module 46 based on the time window judgment, and can improve the accuracy of the beta-gamma coincidence signal judgment by adjusting the time window; the coincidence signal judgment result is used as the trigger signals of the filtering module and the peak value acquisition module, so that the signal processing load of the FPGA can be greatly reduced; with a data buffer FIFO, the activity measurement range of the detector system can be extended.

The general workflow of the coincidence detection device for radioactivity measurement in this embodiment is as follows:

(1) After the radioactive inert gas is separated by a separation concentration system, the radioactive inert gas is filled into a gas measuring chamber 27 of the detector device through a gas inlet and outlet interface 11 under the carrier belt of carrier gas (nitrogen);

(2) After filling, starting to measure;

(3) Monitoring the output signals of the tellurium-zinc-cadmium detectors through the coincidence signal identification module 46;

(4) When there are and only two detector output signals within a given time interval (time window), it is determined that the beta-gamma meets the signal, and a trigger signal is sent to the filtering module 44 and the peak acquisition module 45;

(5) Acquiring coincidence signal energy by a filtering module 44 and a peak acquisition module 45;

(6) Transmitting the coincidence signal energy information to the host computer through the data storage and transmission module 47;

(7) The upper computer recognizes the nuclide species through the coincidence signal energy, draws the coincidence energy spectrum and completes the calculation of the activity concentration of the radioactive gas.

(8) After the measurement is finished, the gas path of the separation and concentration system is used for repeated gas filling (the gas is carrier gas nitrogen) and gas extraction, so that the radioactive gas sample in the cavity is completely removed, and the next measurement can be started.

The invention relates to a semi-regular polyhedron tellurium-zinc-cadmium coincidence detection device suitable for xenon radioactivity measurement, which comprises a spatially symmetrical beta-gamma coincidence detector and a beta-gamma coincidence signal processing system based on an FPGA, wherein the spatially symmetrical beta-gamma coincidence detector consists of a semi-regular polyhedron detector frame and a tellurium-zinc-cadmium detector. The semi-regular polyhedron detector frame comprises a small oblique truncated semi-cube detector frame or a truncated semi-cube detector frame. The tellurium-zinc-cadmium detector is arranged on the square surface of the semi-regular polyhedron detector frame to form a detector group capable of carrying out beta-gamma coincidence measurement on radioactive gas in the frame, and the triangular surface of the semi-regular polyhedron detector frame is used for installing an air inlet interface, an air outlet interface and a test source needle frame interface; the beta-gamma coincidence signal processing system based on the FPGA comprises a detector power supply module, a plurality of pre-amplifiers, a plurality of high-speed ADC, a filtering module, a peak value acquisition module, a coincidence signal identification module and a data storage and transmission module. Compared with the prior art, the invention has the beneficial effects that:

(1) The tellurium-zinc-cadmium detector is much smaller than the high-purity germanium detector or the NaI detector, and works in a normal temperature environment, so that the defects that the high-purity germanium gamma spectrometer and the NaI+plastic scintillator beta-gamma conform to the measurement detection system are large in size, heavy in weight, difficult to maintain, difficult to realize portability, in-situ measurement and the like are overcome;

(2) The tellurium-zinc-cadmium detector can realize the measurement of beta rays relative to a high-purity germanium-gamma spectrometer, has better energy resolution than a NaI detector, adopts the beta-gamma coincidence measurement technology realized by the tellurium-zinc-cadmium detector, can reach lower detection limit relative to the high-purity germanium detector, and has higher measurement precision relative to the NaI detector;

(3) The shape design of the semi-regular polyhedron detector is adopted, compared with the design schemes of other shapes such as cubes, cuboids and the like, on one hand, the space symmetry of each detector can be ensured, the coincidence of measurement and rear-end data processing is facilitated, and on the other hand, under the same measurement cavity volume, the larger coverage rate of the detector face of the detector can be obtained;

(4) The tellurium-zinc-cadmium detector can be used for simultaneously measuring the beta-gamma rays, and the measurement cavity volume can be increased according to the requirement by combining the characteristic of the spatial symmetry of a semi-regular polyhedron design, so that the requirement on air separation and concentration is reduced, and the problems that the traditional beta-gamma coincidence detector and the measurement cavity are limited are solved;

(6) The semi-regular polyhedron detector has the advantages that except for the coverage surface of the detector, a plurality of triangular surfaces which are symmetrical in space are remained, so that the arrangement of the air inlet and the air outlet is facilitated without affecting the symmetry of the detector; meanwhile, the designed test source needle frame solves the problem that radioactive gaseous xenon is not easy to obtain, and the problem that a gaseous detector is not easy to perform performance test.

The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.

Claims (14)

1. A coincidence detection device for radioactivity measurement, which is characterized by comprising a frame, a detector arranged on the frame and an air inlet and outlet interface; a gas measurement chamber is arranged in the frame; the frame is a semi-regular polyhedron and comprises a triangular surface and a square surface, and the detector is arranged on the square surface; the detector is a tellurium-zinc-cadmium detector.

2. The coincidence detecting apparatus of claim 1, wherein the semi-regular polyhedron is a small rhombic truncated semi-cube, consisting of 18 square faces and 8 regular triangular rows of faces.

3. The coincidence detecting apparatus of claim 1, wherein the semi-regular polyhedron is a truncated half-cube, consisting of 6 square faces and 8 regular triangle faces.

4. The coincidence detection apparatus of claim 1, wherein a normal direction of a crystal detection face of the cadmium zinc telluride detector is directed toward a center of the gas measurement chamber.

5. The coincidence detecting apparatus of claim 1, wherein each of the tellurium-zinc-cadmium detectors on the frame has an equivalent geometric position and the same detection efficiency for the gas in the measurement chamber.

6. The coincidence detection apparatus of claim 1, including a test source needle mount interface and a test source needle mount mounted on the test source needle mount interface; the air inlet and outlet interface and the test source needle frame interface are arranged on the triangular surface; the test source probe rack is used for testing the performance of the detector.

7. The coincidence detecting apparatus of claim 6, wherein the test source needle mount includes, in order, a needle mount cap, a seal ring, a needle mount lever, and a radioactive point source, the needle mount lever being mounted to the test source needle mount interface such that the radioactive point source is located within the gas measurement chamber.

8. The coincidence detection apparatus of claim 7, wherein the radioactive point source includes a radioactive source having beta-gamma coincidence decay, a gamma radioactive source, and a beta radioactive source.

9. The coincidence detecting apparatus of claim 1, wherein a side of the square face near the gas measuring chamber is provided with a clamping portion, and a side away from the gas measuring chamber is provided with an outer cover; and an accommodating groove for accommodating the tellurium-zinc-cadmium detector is formed between the clamping part and the outer cover.

10. The coincidence detecting apparatus of any of claims 1-9, comprising a signal processing system including a detector power module, a multi-way preamplifier, a multi-way high speed ADC, a filtering module, a peak acquisition module, a coincidence signal identification module, a data storage and transmission module.

11. The coincidence detecting apparatus of claim 10, wherein the detector power module is configured to provide operating power to the cadmium zinc telluride detector; the multichannel preamplifier is used for amplifying pulse signals output by the tellurium-zinc-cadmium detector; the multi-channel high-speed ADC is used for collecting pulse shape data and digitizing pulse waveforms; the coincidence signal identification module is used for real-time screening of output signals of the multipath pre-amplifier, and when any two paths of signals generate pulse signals in a given coincidence time window, trigger signals and coincidence signal channel numbers are respectively sent to the filtering module and the peak value acquisition module; and after the filtering module receives the trigger signal, pulse waveform data corresponding to the channel number and output by the multi-channel high-speed ADC is obtained, and the peak value obtaining module obtains the peak value in the waveform data and sends the peak value and the channel number to the data storage and transmission module.

12. The coincidence detecting apparatus of claim 11, wherein the coincidence time window is the difference in arrival of two signals coincidentally at a coincidence signal identification module.

13. The coincidence detecting apparatus of claim 11, wherein the channel numbers correspond to two cadmium zinc telluride detector numbers that produce a coincidence signal; the peak, i.e., the peak of the voltage pulse output by the detector, represents the energy of the radiation decaying from the radiation source.

14. Use of a coincidence detection device as claimed in any of claims 1 to 13 in the radiometric measurement of radioactive inert gases.