Novel positron annihilation lifetime-momentum correlation spectrometer and measurement method thereof
By employing a combination of a scintillator and a high-purity germanium detector in a positron annihilation lifetime-momentum correlation spectrometer, along with a digital acquisition module and a data processing module, the problem of low count rate was solved, enabling efficient acquisition of electron density and momentum distribution information within materials and improving the accuracy and resolution of the time spectrum.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-03-13
AI Technical Summary
Existing positron annihilation lifetime-momentum correlation spectrometers have low count rates, and traditional methods are costly to construct, making it difficult to efficiently obtain information on electron density and momentum distribution within materials.
The system employs a combination of two scintillator detectors and two high-purity germanium detectors, along with a digital acquisition module and a data processing module. It acquires and processes pulse signals through four analog input channels, enabling rapid acquisition and processing and improving the counting rate and time resolution.
It significantly improves the count rate of positron annihilation lifetime-momentum correlation spectrometer, broadens its application in materials science, and improves the accuracy and resolution of time spectrum.
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Figure CN121657097A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of positron annihilation nuclear spectrometer technology, specifically relating to a novel positron annihilation lifetime-momentum correlation spectrometer and its measurement method. Background Technology
[0002] Positron spectroscopy is an interdisciplinary application of nuclear physics techniques in materials science. The annihilation parameters of positrons can characterize the microstructure of materials. After decades of development and refinement in fundamental theories and experimental techniques related to positrons, positron-related technologies have seen extensive development and application, finding wide applicability in condensed matter physics, chemistry, and materials science. Common experimental methods in positron annihilation lifetime spectroscopy include positron annihilation lifetime spectroscopy, coincidence Doppler broadening spectroscopy, angular correlation spectroscopy, lifetime-momentum correlation spectroscopy, and slow positron beam techniques. Relying on the advantages of positron spectroscopy, such as non-destructive measurement, self-searching for defects, and high sensitivity to atomic-scale defects, this technique plays an irreplaceable role in defect detection and other fields. The annihilation lifetime distribution of positrons within a material reflects the electron density information within the material. Measuring a large number of positron annihilation lifetimes within a material and statistically analyzing them to form a lifetime distribution map, i.e., the positron annihilation lifetime (PAL) spectrum. The Doppler energy shift of annihilated photons contains information about the electron momentum distribution within the material. Measuring the energy of annihilated photons and statistically analyzing it into an energy distribution map, known as the Doppler broadening (DB) spectrum, allows for the acquisition of more information about positrons and their prime states by measuring the correlation between positron annihilation lifetime and Doppler broadening.
[0003] Based on the different starting signals for lifetime measurement, AMOC technology is mainly divided into two types: (1) using 22 The 1.275 MeV gamma photon accompanying the positron decay of the Na radioactive source serves as the initiation signal, i.e., γγΔE. γ (2) Using the positron itself as the starting signal, i.e., β + γΔE γ Compliant with technology. Among them, β + γΔE γ The coincidence technique directly measures positrons as the starting signal, thus achieving an extremely high count rate. However, its implementation is challenging due to the high cost of constructing accelerators for accelerating slow positron beams. In contrast, traditional positron annihilation lifetime-momentum correlation spectrometers are relatively easier to build.
[0004] In the traditional γγΔE γIn positron annihilation lifetime-momentum correlation spectrometry, 22 The 1.275 MeV gamma photon accompanying the decay of positrons from the Na radioactive source serves as the initiation signal. Upon entering the sample, the positron annihilates with an electron, forming two gamma photons with opposite energies of approximately 511 keV. One photon is collected by a termination detector, serving as the termination signal for the positron lifetime; the other is collected by a high-purity germanium detector to measure the Doppler broadening of the electron-positron pair. To obtain the desired positron annihilation lifetime-momentum correlation spectrum, the AMOC spectrometer requires two scintillator detectors and one HPGe detector to detect the two annihilation photons separately and perform three-way coincidences. This significantly reduces the coincidence count rate, greatly increasing the time required to measure a complete positron annihilation lifetime-momentum correlation spectrum. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a novel positron annihilation lifetime-momentum correlation spectrometer and its measurement method, which can significantly improve the count rate without reducing its temporal and energy resolution.
[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: A novel positron annihilation lifetime-momentum correlation spectrometer, mainly comprising a detector module, a data acquisition module, and a data processing module. The detector module includes two scintillator detectors and two high-purity germanium detectors. Each scintillator detector and each high-purity germanium detector is connected to the data acquisition module, and the data acquisition module is connected to the data processing module; wherein:
[0007] Of the two scintillator detectors, one serves as the initiation scintillator detector, detecting the gamma photons accompanying the positron decay of the radioactive source, which serve as the initiation signal of the positron annihilation lifetime spectrum; the other serves as the termination scintillator detector, detecting the gamma photons generated during positron annihilation, which serve as the termination signal of the positron annihilation lifetime spectrum; the high-purity germanium detector detects the gamma photons generated during positron annihilation and measures the Doppler broadening during positron annihilation.
[0008] A scintillator detector and a high-purity germanium detector are symmetrically arranged on both sides of the radiation source, and both are on a first straight line with the radiation source; another scintillator detector and another high-purity germanium detector are symmetrically arranged on both sides of the radiation source, and both are on a second straight line with the radiation source; at the same time, the first straight line is perpendicular to the second straight line.
[0009] The data acquisition module includes an acquisition device with at least four analog input channels, which acquires the pulse signal output by the detector module and converts the acquired pulse signal into a digital signal and transmits it to the computer.
[0010] The data processing module processes the data acquired by the data acquisition module and plots the processing results as a positron annihilation lifetime-momentum correlation spectrum.
[0011] Furthermore, when either of the two scintillator detectors is used as the starting scintillator detector, the other is used as the ending scintillator detector, and the two are combined to measure the positron annihilation lifetime spectrum.
[0012] A high-purity germanium detector, along with a scintillator detector serving as a termination scintillator detector and a radiation source, is positioned in a straight line to acquire the Doppler broadened energy spectrum measurement signal during positron annihilation.
[0013] Furthermore, the initiating scintillator detector is used to detect... 22 The 1.275 MeV γ photon accompanying the positron decay of the Na radioactive source serves as the starting signal for the positron annihilation lifetime spectrum; the termination scintillator detector is used to detect the 511 KeV γ photon generated during positron annihilation, serving as the termination signal for the positron annihilation lifetime spectrum; the high-purity germanium detector is used to receive and detect the 511 KeV γ photon generated during positron annihilation and to measure the Doppler broadening during positron annihilation.
[0014] Furthermore, the acquisition device having at least four analog input channels is a data acquisition card or an oscilloscope;
[0015] The four analog input channels are numbered as Channel 1, Channel 2, Channel 3, and Channel 4, respectively; Channel 1 and Channel 2 are each connected to a scintillator detector, and Channel 3 and Channel 4 are each connected to a high-purity germanium detector.
[0016] Furthermore, in the data processing module, a data acquisition program is used to connect to the data acquisition device to acquire and process the acquired pulse data; the required pulse data is screened and identified and matched, and after the measurement is completed, the results are plotted as a positron annihilation lifetime-momentum correlation spectrum.
[0017] The pulse data are derived from the start signal of the positron annihilation lifetime spectrum measured by the start scintillator detector, the end signal of the positron annihilation lifetime spectrum measured by the end scintillator detector, and the Doppler broadened energy spectrum measurement signals from the two high-purity germanium detectors.
[0018] Furthermore, the data acquisition program processes the acquired pulse data as follows:
[0019] First, the first and second channels are set with logic trigger signals. When a start signal indicating the generation of a positron that meets the requirements appears in either the first or second channel, a first trigger time window is triggered. Within the first trigger time window, if a termination signal indicating the annihilation of a positron that also meets the requirements is found in another channel of the first or second channel, it indicates that the trigger event meets the requirements. Then, the data acquisition program fits the signals that meet the requirements, performs baseline correction and smoothing, and after processing, performs pulse discrimination and data timing operations to obtain positron annihilation lifetime data.
[0020] While achieving data timing, a trigger signal is generated and a second trigger time window is triggered. Within the second trigger time window, the energy signals of the third and fourth channels are searched to find the Doppler broadening energy signal measured during positron annihilation that matches the current trigger event. Finally, the Doppler broadening of the positron annihilation lifetime and the positron-electron annihilation pair triggered in this event is captured and saved as a coincidence event of positron annihilation lifetime-momentum correlation.
[0021] Furthermore, at least ten million coincidence events were collected, and two-dimensional histogram frequency statistics were performed on them to obtain the positron annihilation lifetime-momentum correlation spectrum.
[0022] This invention also provides a novel method for measuring positron annihilation lifetime-momentum correlation spectra, based on the aforementioned novel positron annihilation lifetime-momentum correlation spectrometer, the method comprising the following steps:
[0023] S1. Connect all modules of the positron annihilation lifetime-momentum correlation spectrometer and start the radiation source;
[0024] S2, the first channel and the second channel setting or logic trigger signal, when the starting signal emitted when a positron is generated that meets the requirements appears in either the first channel or the second channel, triggers the first trigger time window; within the first trigger time window, as long as the termination signal emitted when a positron annihilation that meets the requirements is found in the other channel of the first channel or the second channel, it indicates that the trigger event meets the requirements; then, the data acquisition program fits the signals that meet the requirements, and performs baseline correction and smoothing processing, and after processing, performs pulse discrimination and data timing operations to finally obtain positron annihilation lifetime data;
[0025] S3. While realizing data timing, a trigger signal is generated to trigger the second trigger time window. Within the second trigger time window, the energy signals of the third and fourth channels are searched respectively. The Doppler broadening energy signal measured during positron annihilation that matches the current trigger event is found. Finally, the Doppler broadening of the positron annihilation lifetime and the positron-electron annihilation pair triggered this time is captured and saved as a coincidence event of positron annihilation lifetime-momentum correlation.
[0026] S4. Collect at least ten million coincidence events and perform two-dimensional histogram frequency statistics on them to obtain the positron annihilation lifetime-momentum correlation spectrum, so as to ensure the statistical validity of the positron annihilation lifetime-momentum correlation spectrum.
[0027] S5. Turn off the radiation source.
[0028] Furthermore, the first trigger time window is 120 nanoseconds.
[0029] Furthermore, the second trigger time window is 10 microseconds.
[0030] The beneficial effects of this invention are as follows: The novel positron annihilation lifetime-momentum correlation spectrometer and its measurement method provided by this invention mainly include a detector module, a data acquisition module, and a data processing module. The detector module includes two scintillator detectors and two high-purity germanium detectors. Each scintillator detector and each high-purity germanium detector is connected to the data acquisition module, which is connected to the data processing module. Of the two scintillator detectors, one serves as the starting scintillator detector, detecting the starting signal of the positron annihilation lifetime spectrum; the other serves as the ending scintillator detector, detecting the ending signal of the positron annihilation lifetime spectrum. The high-purity germanium detector measures the Doppler broadening during positron annihilation. The data acquisition module includes an acquisition device with at least four analog input channels, which acquires the pulse signals output by the detector module and converts the acquired pulse signals into digital signals for transmission to a computer. The data processing module processes the data acquired by the data acquisition module and plots the processing results as a positron annihilation lifetime-momentum correlation spectrum.
[0031] The novel positron annihilation lifetime-momentum correlation spectrometer provided by this invention, with its arrangement of two scintillator detectors and two high-purity germanium detectors, avoids the problem in existing three-way coincidence correlation spectrometers where the scintillator detector, not aligned with the high-purity germanium detector and the radiation source, is used as the terminating scintillator detector. This prevents the acquisition of the Doppler broadened energy spectrum measurement signal of 511 keV γ photons generated by positron annihilation. Consequently, it significantly improves the acquisition efficiency of the positron annihilation lifetime-momentum correlation spectrometer, thereby increasing its count rate and broadening the application of this technology in the field of materials science.
[0032] Compared to existing positron annihilation lifetime-momentum correlation measurement techniques, this embodiment uses a digital acquisition module and a programmable data processing module to achieve rapid acquisition and processing of pulse signals, thereby improving the resolution of time measurement and the accuracy of the time spectrum. Attached Figure Description
[0033] Figure 1 A schematic diagram of an existing positron lifetime-momentum correlation measurement system;
[0034] Figure 2 A schematic diagram of a novel positron annihilation lifetime-momentum correlation spectrometer provided for embodiments of the present invention;
[0035] Figure 3 A schematic diagram of a data processing module provided for an embodiment of the present invention;
[0036] Among them, 1—first channel, 2—second channel, 3—third channel, and 4—fourth channel. Detailed Implementation
[0037] The technical solutions in the embodiments of the present invention will be further clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0038] It should be noted that in the description of the embodiments of the present invention, the terms "upper," "lower," "front," "rear," "front," "back," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0039] For example Figure 1 The traditional γγΔE shown γIn coincidence positron annihilation lifetime-momentum correlation spectrometers, in order to obtain the desired positron annihilation lifetime-momentum correlation spectrum, the AMOC spectrometer requires two scintillator detectors and one HPGe detector to detect two annihilated photons separately and perform three-way coincidence. This results in a significant reduction in the coincidence count rate and a substantial increase in the time required to measure a complete positron annihilation lifetime-momentum correlation spectrum. This application proposes a novel positron annihilation lifetime-momentum correlation spectrometer, which aims to significantly improve the count rate without reducing its temporal and energy resolution.
[0040] like Figure 2 As shown in the figure, an embodiment of the present invention provides a novel positron annihilation lifetime-momentum correlation spectrometer. The positron annihilation lifetime-momentum correlation spectrometer mainly includes a detector module, a data acquisition module, and a data processing module. The detector module includes two scintillator detectors and two high-purity germanium detectors. Each scintillator detector and each high-purity germanium detector is connected to the data acquisition module, and the data acquisition module is connected to the data processing module. Wherein:
[0041] Of the two scintillator detectors, one serves as the starting scintillator detector and the other as the ending scintillator detector. The starting scintillator detector is mainly used for detection. 22 The 1.275 MeV γ photon accompanying the positron decay of the Na radioactive source serves as the starting signal for the positron annihilation lifetime spectrum; the termination scintillator detector is used to detect the 511 KeV γ photon generated during positron annihilation, serving as the termination signal for the positron annihilation lifetime spectrum.
[0042] The high-purity germanium detector is used to receive and detect 511 keV γ photons generated by positron annihilation and to measure the Doppler broadening during positron annihilation. One scintillator detector and one high-purity germanium detector are symmetrically arranged on both sides of the radiation source, and both are on a first straight line with the radiation source; another scintillator detector and another high-purity germanium detector are symmetrically arranged on both sides of the radiation source, and both are on a second straight line with the radiation source; simultaneously, the first straight line is perpendicular to the second straight line.
[0043] When one of the two scintillator detectors is used as the starting scintillator detector and the other as the ending scintillator detector, the two are combined to measure the positron annihilation lifetime spectrum. A high-purity germanium detector, which is aligned with the ending scintillator detector and the radiation source, is used to acquire the Doppler broadened energy spectrum measurement signal during positron annihilation.
[0044] The configuration of two scintillator detectors and two high-purity germanium detectors in this embodiment avoids the problem in existing three-way coincidence correlation spectrometers where the scintillator detector, not aligned with the high-purity germanium detector and the radiation source, is used as the terminating scintillator detector, making it impossible to acquire the Doppler broadened energy spectrum measurement signal of 511 keV γ photons generated by positron annihilation. This significantly improves the acquisition efficiency of the positron annihilation lifetime-momentum correlation spectrometer, thereby increasing its count rate and broadening its application in materials science.
[0045] The data acquisition module includes an acquisition device with at least four analog input channels, numbered as Channel 1, Channel 2, Channel 3, and Channel 4. Channel 1 and Channel 2 are each connected to a scintillator detector and are used to acquire the pulse signals output by each scintillator detector in the detector module. Channel 3 and Channel 4 are each connected to a high-purity germanium detector and are used to acquire the pulse signals output by each high-purity germanium detector in the detector module. The acquired pulse signals are preprocessed and converted into digital signals for transmission to the computer.
[0046] The data processing module is mainly used to process the acquired data and plot the processing results as a positron annihilation lifetime-momentum correlation spectrum. The data mainly comes from the start signal of the positron annihilation lifetime spectrum of the initiating scintillator detector, the energy spectrum measurement signal of the high-purity germanium detector, and the termination signal of the positron annihilation lifetime spectrum of the terminating scintillator detector.
[0047] Optionally, the acquisition device is a data acquisition card or an oscilloscope, used to acquire the pulse signal output by the detector module and convert the acquired pulse signal into a digital signal to be transmitted to a computer.
[0048] Specifically, the data acquisition module uses an oscilloscope or acquisition card with four analog input channels to acquire pulse signals. It is responsible for acquiring the pulse signals output by the two scintillator detectors and the two high-purity germanium detectors in the detector module, converting the acquired pulse signals into digital signals, and then transmitting and storing the data in the form of digital signals in the computer.
[0049] In one specific embodiment, the data acquisition module uses a Pixie-4 Express digital acquisition card with four analog input channels, a theoretical analog bandwidth of 800MHz, a data sampling rate of 500msps, a vertical resolution of 14 bits, and a 256MB memory buffer. The acquisition card's API allows for free programming using a software development kit to design the desired functions. The four analog input channels are numbered as Channel 1, Channel 2, Channel 3, and Channel 4.
[0050] In another specific embodiment, the data processing module is as follows: Figure 3 As shown, the main components include: connecting a data acquisition device (oscilloscope or acquisition card) to a computer using a written data acquisition program to acquire and process the acquired pulse data (i.e., transferring the digitized data to the computer, where the data processing module then processes the acquired pulse data). The required pulse data is screened and matched, and after the measurement is completed, the results are plotted as a positron annihilation lifetime-momentum correlation spectrum. The pulse data originates from the starting signal of the positron annihilation lifetime spectrum measured by the starting scintillator detector, the ending signal of the positron annihilation lifetime spectrum measured by the ending scintillator detector, and the Doppler broadened energy spectrum measurement signals from two high-purity germanium detectors.
[0051] Specifically, a data acquisition program is written on a computer and used to connect to a data acquisition device (i.e., an acquisition card). The acquisition device is then used to acquire and preprocess the acquired pulse data (pulse signals). Specifically, channel 1 and channel 2 acquire the time signals of positron generation and annihilation from the scintillator detector, respectively, while channel 3 and channel 4 acquire the Doppler broadened energy spectrum signals measured by the high-purity germanium detector, respectively.
[0052] The subsequent data acquisition program processes the received pulse data: First, the first channel 1 and the second channel 2 are set with logic trigger signals. A start signal is emitted whenever a positron is generated that meets the requirements in either the first channel 1 or the second channel 2. 22 The decay of a Na radioactive source producing positrons and the accompanying 1.275 MeV gamma photon triggers a first trigger time window of 120 nanoseconds. Within this first trigger time window, if a termination signal (a 511 keV gamma photon generated during positron annihilation) matching the requirements is found in either channel 1 (first channel 1) or another channel 2 (second channel 2), the trigger event is considered to be compliant. The data acquisition program fits the compliant signal, performs baseline correction and smoothing, and then performs pulse discrimination and data timing operations to obtain positron annihilation lifetime data. Simultaneously, a trigger signal is generated at the same time, triggering a second trigger time window of 10 microseconds. Within this second trigger time window, the energy signals in channels 3 (third channel 3) and 4 (fourth channel 4) are searched to find the Doppler broadening energy signal measured during positron annihilation that matches the current trigger event. Finally, the Doppler broadening of the positron annihilation lifetime and the positron-electron annihilation pair is captured and saved as a coincidence event of positron annihilation lifetime-momentum correlation.
[0053] To ensure the statistical validity of the final positron annihilation lifetime-momentum correlation spectrum, at least ten million coincidence events need to be collected and subjected to two-dimensional histogram frequency statistics to obtain the positron annihilation lifetime-momentum correlation spectrum.
[0054] Based on the measurement principle of the positron annihilation lifetime-momentum correlation spectrometer provided in this embodiment, and the control logic of the data acquisition program for pulse data processing therein, industrial design technicians in the art can use known industrial control programs to perform industrial automation control of the data acquisition program for the acquisition and processing of the acquired pulse data and other related operating processes in the data processing module.
[0055] Compared to existing positron annihilation lifetime-momentum correlation measurement techniques, this embodiment uses a digital acquisition module and a programmable data processing module to achieve rapid acquisition and processing of pulse signals, thereby improving the resolution of time measurement and the accuracy of the time spectrum.
[0056] This invention also provides a novel method for measuring positron annihilation lifetime-momentum correlation spectra, based on the novel positron annihilation lifetime-momentum correlation spectrometer, the method comprising the following steps:
[0057] S1. Connect all modules of the positron annihilation lifetime-momentum correlation spectrometer and start the radiation source;
[0058] S2, the first channel and the second channel setting or logic trigger signal, when a start signal is emitted when a positron that meets the requirements is generated in either the first channel 1 or the second channel 2, triggers the first trigger time window; within the first trigger time window, as long as a termination signal emitted when a positron that meets the requirements is annihilated is found in the other channel of the first channel 1 or the second channel 2, it indicates that the trigger event meets the requirements; then, the data acquisition program fits the signals that meet the requirements, and performs baseline correction and smoothing processing. After processing, pulse discrimination and data timing operations are performed to finally obtain the positron annihilation lifetime data;
[0059] Specifically, the first trigger time window is 120 nanoseconds.
[0060] S3. While realizing data timing, a trigger signal is generated to trigger the second trigger time window. Within the second trigger time window, the energy signals of the third channel 3 and the fourth channel 4 are searched respectively. The Doppler broadening energy signal measured during positron annihilation that matches the current trigger event is found. Finally, the positron annihilation lifetime and the Doppler broadening of the positron-electron annihilation pair triggered this time are captured and saved as a coincidence event of positron annihilation lifetime-momentum correlation.
[0061] Specifically, the second trigger time window is 20 microseconds.
[0062] S4. Collect at least ten million coincidence events and perform two-dimensional histogram frequency statistics on them to obtain the positron annihilation lifetime-momentum correlation spectrum, so as to ensure the statistical validity of the positron annihilation lifetime-momentum correlation spectrum.
[0063] S5. Turn off the radiation source.
[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.
Claims
1. A novel positron annihilation lifetime-momentum correlation spectrometer, characterized in that, It mainly includes a detector module, a data acquisition module, and a data processing module. The detector module includes two scintillator detectors and two high-purity germanium detectors. Each scintillator detector and each high-purity germanium detector is connected to the data acquisition module, which is connected to the data processing module. Of the two scintillator detectors, one serves as the initiation scintillator detector, detecting the gamma photons accompanying the positron decay of the radioactive source, which serve as the initiation signal of the positron annihilation lifetime spectrum; the other serves as the termination scintillator detector, detecting the gamma photons generated during positron annihilation, which serve as the termination signal of the positron annihilation lifetime spectrum; the high-purity germanium detector detects the gamma photons generated during positron annihilation and measures the Doppler broadening during positron annihilation. A scintillator detector and a high-purity germanium detector are symmetrically arranged on both sides of the radiation source, and both are on a first straight line with the radiation source; another scintillator detector and another high-purity germanium detector are symmetrically arranged on both sides of the radiation source, and both are on a second straight line with the radiation source; at the same time, the first straight line is perpendicular to the second straight line. The data acquisition module includes an acquisition device with at least four analog input channels, which acquires the pulse signal output by the detector module and converts the acquired pulse signal into a digital signal and transmits it to the computer. The data processing module processes the data acquired by the data acquisition module and plots the processing results as a positron annihilation lifetime-momentum correlation spectrum.
2. The novel positron annihilation lifetime-momentum correlation spectrometer according to claim 1, characterized in that, When one of the two scintillator detectors is used as the starting scintillator detector, the other is used as the ending scintillator detector. The two are combined to measure the positron annihilation lifetime spectrum. A high-purity germanium detector, along with a scintillator detector serving as a termination scintillator detector and a radiation source, is positioned in a straight line to acquire the Doppler broadened energy spectrum measurement signal during positron annihilation.
3. A novel positron annihilation lifetime-momentum correlation spectrometer according to claim 1, characterized in that, The initiating scintillator detector is used for detection 22 The 1.275 MeV γ photon accompanying the positron decay of the Na radioactive source serves as the starting signal for the positron annihilation lifetime spectrum; the termination scintillator detector is used to detect the 511 KeV γ photon generated during positron annihilation, serving as the termination signal for the positron annihilation lifetime spectrum; the high-purity germanium detector is used to receive and detect the 511 KeV γ photon generated during positron annihilation and to measure the Doppler broadening during positron annihilation.
4. A novel positron annihilation lifetime-momentum correlation spectrometer according to claim 1, characterized in that, The acquisition device having at least four analog input channels is a data acquisition card or an oscilloscope; The four analog input channels are numbered as Channel 1, Channel 2, Channel 3, and Channel 4, respectively; Channel 1 and Channel 2 are each connected to a scintillator detector, and Channel 3 and Channel 4 are each connected to a high-purity germanium detector.
5. A novel positron annihilation lifetime-momentum correlation spectrometer according to claim 4, characterized in that, In the data processing module, a data acquisition program is used to connect to the data acquisition device to acquire and process the acquired pulse data; the required pulse data is screened and identified and matched, and after the measurement is completed, the results are plotted as a positron annihilation lifetime-momentum correlation spectrum. The pulse data are derived from the start signal of the positron annihilation lifetime spectrum measured by the start scintillator detector, the end signal of the positron annihilation lifetime spectrum measured by the end scintillator detector, and the Doppler broadened energy spectrum measurement signals from the two high-purity germanium detectors.
6. A novel positron annihilation lifetime-momentum correlation spectrometer according to claim 5, characterized in that, The data acquisition program processes the acquired pulse data as follows: First, the first and second channels are set with logic trigger signals. When a start signal indicating the generation of a positron that meets the requirements appears in either the first or second channel, a first trigger time window is triggered. Within the first trigger time window, if a termination signal indicating the annihilation of a positron that also meets the requirements is found in another channel of the first or second channel, it indicates that the trigger event meets the requirements. Then, the data processing program fits the signals that meet the requirements, performs baseline correction and smoothing, and after processing, performs pulse discrimination and data timing operations to obtain positron annihilation lifetime data. While achieving data timing, a trigger signal is generated and a second trigger time window is triggered. Within the second trigger time window, the energy signals of the third and fourth channels are searched to find the Doppler broadening energy signal measured during positron annihilation that matches the current trigger event. Finally, the Doppler broadening of the positron annihilation lifetime and the positron-electron annihilation pair triggered in this event is captured and saved as a coincidence event of positron annihilation lifetime-momentum correlation.
7. A novel positron annihilation lifetime-momentum correlation spectrometer according to claim 6, characterized in that, At least ten million coincidence events were collected, and two-dimensional histogram frequency statistics were performed on them to obtain the positron annihilation lifetime-momentum correlation spectrum.
8. A novel method for measuring positron annihilation lifetime-momentum correlation spectra, performed using the novel positron annihilation lifetime-momentum correlation spectrometer described in any one of claims 1-7, characterized in that... The method includes the following steps: S1. Connect all modules of the positron annihilation lifetime-momentum correlation spectrometer and start the radiation source; S2, the first channel and the second channel setting or logic trigger signal, when the starting signal emitted when a positron is generated that meets the requirements appears in either the first channel or the second channel, triggers the first trigger time window; within the first trigger time window, as long as the termination signal emitted when a positron annihilation that meets the requirements is found in the other channel of the first channel or the second channel, it indicates that the trigger event meets the requirements; then, the data acquisition program fits the signals that meet the requirements, and performs baseline correction and smoothing processing, and after processing, performs pulse discrimination and data timing operations to finally obtain positron annihilation lifetime data; S3. While realizing data timing, a trigger signal is generated to trigger the second trigger time window. Within the second trigger time window, the energy signals of the third and fourth channels are searched respectively. The Doppler broadening energy signal measured during positron annihilation that matches the current trigger event is found. Finally, the Doppler broadening of the positron annihilation lifetime and the positron-electron annihilation pair triggered this time is captured and saved as a coincidence event of positron annihilation lifetime-momentum correlation. S4. Collect at least ten million coincidence events and perform two-dimensional histogram frequency statistics on them to obtain the positron annihilation lifetime-momentum correlation spectrum, so as to ensure the statistical validity of the positron annihilation lifetime-momentum correlation spectrum. S5. Turn off the radiation source.
9. The method for measuring the novel positron annihilation lifetime-momentum correlation spectrum according to claim 8, characterized in that, The first trigger time window is 120 nanoseconds.
10. The method for measuring the novel positron annihilation lifetime-momentum correlation spectrum according to claim 8, characterized in that, The second trigger time window is 10 microseconds.