Two-dimensional positron annihilation lifetime spectrum measurement method and system

Abstract

The present disclosure relates to a two-dimensional positron annihilation lifetime spectrum measurement method and system, which relates to the fields of nuclear spectroscopy and nuclear detection technology. This method detects the first stop time and the second stop time of the two annihilation gamma photons generated in the reverse direction when the positron annihilates, respectively. The first lifetime value and the second lifetime value are then calculated from the start time of the initial gamma photon generated by the decay of the radioactive source, respectively. The first lifetime value and the second lifetime value are then subjected to two-dimensional statistics to obtain a two-dimensional positron annihilation lifetime spectrum of the positron annihilation in the sample to be tested. This method performs statistics on the two annihilation gamma photons generated by an annihilation case, which can effectively eliminate background counts, thereby improving the peak-to-valley ratio of the lifetime spectrum, and can improve the utilization rate of the annihilation gamma photon information in the annihilation case, thereby improving the time resolution of the measurement.

Description

Technical Field

[0001] The present disclosure relates to the field of nuclear spectroscopy and nuclear detection technology, and in particular to a two-dimensional positron annihilation lifetime spectrum measurement method and system. Background Art

[0002] Positron Annihilation Lifetime Spectrum (PALS) is a measurement method that characterizes the type and number of material defects by measuring the annihilation lifetime of positrons in matter. When a radioactive source decays and releases a positron, it also emits an initial gamma photon of a specific energy. When the positron annihilates, it produces two annihilation gamma photons of specific energies in the opposite direction. The energy signals of the initial and annihilation gamma photons can be detected during the measurement, and the annihilation lifetime of the positron from its generation to its annihilation is calculated based on the time difference between the energy signals.

[0003] Currently, in the measurement of positron annihilation lifetime spectrum, two detectors are usually used to detect the occurrence time of the energy signal of an initial γ photon as the start time of positron generation, and the occurrence time of an annihilation γ photon as the stop time of positron generation. The annihilation lifetime of the positron is then calculated based on the start time and stop time.

[0004] The peak-to-valley ratio is a key metric for measuring the accuracy of positron annihilation lifetime spectrum measurements. However, the aforementioned scheme may have difficulty distinguishing some background counts, leaving the peak-to-valley ratio of the positron annihilation lifetime spectrum to be improved. Furthermore, detecting the occurrence time of an annihilating gamma photon as the stopping time also results in low utilization of the annihilating gamma photon information, leaving room for improvement in the temporal resolution of the aforementioned scheme.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the Invention

[0006] The purpose of the present disclosure is to provide a two-dimensional positron annihilation lifetime spectrum measurement method and system. During the measurement process, this method detects two annihilation gamma photons generated in the opposite direction by positron annihilation on the first side and the second side opposite to the sample to be measured, respectively. This method can effectively eliminate background counts in the measurement and further improve the peak-to-valley ratio; and more fully utilize the annihilation gamma photon information to improve the time resolution of the measurement, thereby improving the measurement accuracy of the positron annihilation lifetime spectrum.

[0007] According to a first aspect of the present disclosure, a two-dimensional positron annihilation lifetime spectrum measurement method is provided, which may include:

[0008] Detecting the start time of a first energy signal generated by decay of a radioactive source, wherein an energy threshold of the first energy signal is set according to the energy of a starting gamma photon generated by decay of the radioactive source;

[0009] Detecting a first stop time of generating a second energy signal on a first side of the sample to be tested, and detecting a second stop time of generating a third energy signal on a second side of the sample to be tested, wherein energy thresholds of the second energy signal and the third energy signal are set according to the energy of annihilation gamma photons generated by positron annihilation, and the first side is opposite to the second side;

[0010] When the first stop time meets the first recording condition, a first life value is calculated based on the start time and the first stop time;

[0011] When the second stop time meets the second recording condition, a second life value is calculated based on the start time and the second stop time;

[0012] When the first lifetime value and the second lifetime value are obtained, two-dimensional statistics are performed on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum.

[0013] Optionally, the first recording condition includes a start time and a first stop time obtained within a first preset time window.

[0014] Optionally, the second recording condition includes that the start time and the second stop time are obtained within a second preset time window.

[0015] Optionally, when the first lifetime value and the second lifetime value are obtained, performing two-dimensional statistics on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum includes:

[0016] When the first life value and the second life value are obtained, two-dimensional statistics are performed with the first life value as the horizontal axis and the second life value as the vertical axis;

[0017] When the difference between the first lifetime value and the second lifetime value is smaller than the preset time difference, a two-dimensional positron annihilation lifetime spectrum is obtained according to the first lifetime value and the second lifetime value.

[0018] Optionally, the first stop time corresponds to a first time resolution, the second stop time corresponds to a second time resolution, and the ratio of the first time resolution to the second time resolution is less than

[0019] According to a second aspect of the present disclosure, a two-dimensional positron annihilation lifetime spectrum measurement system is provided, which may include:

[0020] A start time recording module, used to detect the start time of the first energy signal generated by the decay of the radioactive source, wherein the energy threshold of the first energy signal is set according to the energy of the starting gamma photon generated by the decay of the radioactive source;

[0021] A first stop time recording module is used to detect a first stop time when a second energy signal is generated on a first side of the sample to be tested, wherein an energy threshold of the second energy signal is set according to an energy of an annihilation gamma photon generated by positron annihilation;

[0022] a second stop time recording module, configured to detect a second stop time when a third energy signal is generated on a second side of the sample to be tested, wherein an energy threshold of the third energy signal is set according to an energy of an annihilation gamma photon generated by positron annihilation, and the first side is opposite to the second side;

[0023] A life value calculation module, configured to obtain a first life value by calculating the first life value according to the start time and the first stop time when the first stop time meets the first recording condition;

[0024] The life value calculation module is further configured to obtain a second life value by calculating based on the start time and the second stop time when the second stop time meets the second recording condition;

[0025] The two-dimensional lifetime spectrum statistics module is used to perform two-dimensional statistics on the first lifetime value and the second lifetime value when the first lifetime value and the second lifetime value are obtained, so as to obtain a two-dimensional positron annihilation lifetime spectrum.

[0026] Optionally, the first stop time recording module includes:

[0027] a first stop detector, configured to detect a second energy signal on a first side of the sample to be tested;

[0028] a first time extraction unit, configured to extract the occurrence time of the second energy signal to obtain a first stop time when the second energy signal reaches 0.511 MeV;

[0029] Optionally, the second stop time recording module includes:

[0030] a second stop detector, configured to detect a third energy signal on a second side of the sample to be tested;

[0031] The second time extraction unit is configured to extract the occurrence time of the third energy signal to obtain the second stop time when the third energy signal reaches 0.511 MeV.

[0032] Optionally, the first stop time recording module corresponds to a first time resolution, the second stop time recording module corresponds to a second time resolution, and the ratio of the first time resolution to the second time resolution is less than

[0033] Optionally, a two-dimensional lifetime spectrum statistics module includes:

[0034] A life value statistics unit is used to perform two-dimensional statistics with the first life value as the horizontal axis and the second life value as the vertical axis when the first life value and the second life value are obtained;

[0035] The lifetime value extraction unit is used to obtain a two-dimensional positron annihilation lifetime spectrum according to the first lifetime value and the second lifetime value when the difference between the first lifetime value and the second lifetime value is less than a preset time difference.

[0036] Optionally, the first recording condition includes a start time and a first stop time obtained within a first preset time window.

[0037] Optionally, the second recording condition includes that the start time and the second stop time are obtained within a second preset time window.

[0038] Optionally, the start time recording module includes:

[0039] an initial detector, configured to detect a first energy signal from a radiation source;

[0040] The third time extraction unit is configured to extract the occurrence time of the first energy signal to obtain the start time when the first energy signal reaches 1.28 MeV.

[0041] According to a third aspect of the present disclosure, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the method of the first aspect is implemented.

[0042] According to a fourth aspect of the present disclosure, there is provided an electronic device, including:

[0043] processor; and

[0044] a memory for storing executable instructions for the processor;

[0045] The processor is configured to implement the method of the first aspect by executing executable instructions.

[0046] The present disclosure provides a two-dimensional positron annihilation lifetime spectrum measurement method, which detects the start time of a first energy signal generated by the decay of a radioactive source, the first stop time of a second energy signal generated by the first side of a sample to be tested, and the second stop time of a third energy signal generated by the second side of the sample to be tested, wherein the energy threshold of the first energy signal is set according to the energy of the starting gamma photon generated by the decay of the radioactive source, and the energy thresholds of the second energy signal and the third energy signal are set according to the energy of the annihilation gamma photon generated by positron annihilation, and the first side is opposite to the second side; when the acquisition of the first stop time meets the first recording condition, a first lifetime value is calculated according to the start time and the first stop time; when the acquisition of the second stop time meets the second recording condition, a second lifetime value is calculated according to the start time and the second stop time; and then two-dimensional statistics are performed on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum of positrons annihilated in the sample to be tested.

[0047] The disclosed two-dimensional positron annihilation lifetime spectrum measurement method detects two annihilation gamma photons generated by an annihilation event during the measurement process, obtains their respective first and second stop times, and then performs two-dimensional statistics on the lifetime of the annihilation event based on the first and second stop times. This method can effectively eliminate background counts in the measurement, reduce the occasional introduction of erroneous events, and further improve the peak-to-valley ratio. Furthermore, it can improve the utilization rate of annihilation gamma photon information, thereby enhancing the temporal resolution of the measurement. This method effectively improves the measurement accuracy of the positron annihilation lifetime by improving the peak-to-valley ratio and temporal resolution.

[0048] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0050] Figure 1 The following is a schematic diagram illustrating the structure of a conventional positron annihilation lifetime spectrum measurement system.

[0051] Figure 2 A schematic diagram illustrating a conventional positron annihilation lifetime spectrum.

[0052] Figure 3 A schematic flow chart illustrating a two-dimensional positron annihilation lifetime spectrum measurement method in an embodiment of the present disclosure is illustrated.

[0053] Figure 4 A schematic diagram of a process for statistical two-dimensional positron annihilation lifetime spectrum in an embodiment of the present disclosure is illustrated.

[0054] Figure 5 A schematic diagram of a two-dimensional positron annihilation lifetime spectrum in an embodiment of the present disclosure is illustrated.

[0055] Figure 6 A schematic diagram illustrating the annihilation lifetime diagonalization process in an embodiment of the present disclosure is shown.

[0056] Figure 7 One of the structural schematic diagrams of a two-dimensional positron annihilation lifetime spectrum measurement system in an embodiment of the present disclosure is illustrated.

[0057] Figure 8 One of the structural schematic diagrams of a two-dimensional positron annihilation lifetime spectrum measurement system in an embodiment of the present disclosure is illustrated.

[0058] Figure 9 A schematic structural diagram of an electronic device according to an embodiment of the present disclosure is illustrated. DETAILED DESCRIPTION

[0059] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present disclosure will be more comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or that other methods, components, devices, steps, etc. may be employed. In other cases, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0060] In addition, the accompanying drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. Identical reference numerals in the figures denote identical or similar parts, and thus repetitive descriptions thereof will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities that do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0061] Positrons are the antiparticles of electrons. Upon contact with an atom's extranuclear electrons in matter, they annihilate, producing two oppositely directed gamma photons with energies of 0.511 MeV. The positron's annihilation lifetime, τ, is directly related to the electron density at the site of annihilation. Because vacancy defects in matter are typically electronegative due to the absence of an atomic core, they are more susceptible to capturing positrons, and the electron density at defects is typically lower than that of the matrix. Therefore, the annihilation lifetime of positrons at defects is longer than that at the matrix. Generally, different components of the annihilation lifetime can characterize different types of defects, and the strength of the annihilation lifetime of different components can characterize the number of different types of defects. Measuring the annihilation lifetime of positrons in matter can be used to characterize the types and number of defects in a material.

[0062] Figure 1 A schematic structural diagram of a conventional positron annihilation lifetime spectrum measurement system 100 is shown as follows: Figure 1 As shown, a conventional PALS measurement system is usually composed of a radioactive source-sample to be measured, a start detector 110, a stop detector 120, a start time extraction unit 130, a stop time extraction unit 140, a time difference calculation unit 150, and a statistical unit 160. The radioactive source is usually 22 Na radioactive source, 22 When Na decays to produce a positron, it also emits an initial gamma photon with an energy of 1.28 MeV. Therefore, the 1.28 MeV gamma photon energy signal can be detected as the annihilation start signal. The start detector 110 detects the 1.28 MeV start gamma photon signal, and the stop detector 120 detects a 0.511 MeV annihilation gamma photon signal. The start time extraction unit 130 and the stop time extraction unit 140, connected to each unit, extract the start time of the start gamma photon signal, and the stop time of the annihilation gamma photon signal. The time difference calculation unit 150 then calculates the positron annihilation lifetime based on the start and stop times. The statistics unit 160 then performs statistics on the positron annihilation lifetime to obtain a conventional positron annihilation lifetime spectrum.

[0063] It can be seen that the conventional positron annihilation lifetime spectrum measurement system 100 uses one stop detector 120 to detect one annihilation gamma photon, and the utilization rate of the annihilation gamma photon information in the annihilation case is low, thereby affecting the time resolution of the measurement and further affecting the measurement accuracy.

[0064] Figure 2 A schematic diagram of a conventional positron annihilation lifetime spectrum is shown below. Figure 2 As shown in the figure, the spectrum is a one-dimensional statistical representation of the positron annihilation lifetime measured from channel 1 (channel 1) on the horizontal axis, and the vertical axis represents the normalized (NormalizedN) counts of different lifetime values. At this time, the positron annihilation lifetime spectrum F(t) can be expressed by the following formula (1):

[0065]

[0066] Among them, L(t) is the ideal positron annihilation lifetime spectrum function, R(t) is the system time resolution, and B is the background.

[0067] Furthermore, the ideal positron lifetime spectrum function L(t) is a superposition of multiple exponential functions and can be expressed by the following formula (2):

[0068]

[0069] Where n is the number of lifetime components of positron annihilation in the sample to be tested, N0 is the total intensity of the positron lifetime spectrum, I i is the relative intensity of the i-th lifetime component, τ i is the lifespan value of the i-th lifespan component.

[0070] From the above content, it can be seen that background B is also an important factor affecting the accuracy of conventional positron annihilation lifetime spectrum measurement.

[0071] In an embodiment of the present disclosure, a two-dimensional positron annihilation lifetime spectrum measurement method is provided. The method obtains the starting time of the initial gamma photon generated by the decay of a radioactive source, and obtains the first stop time and the second stop time of the two annihilation gamma photons generated in reverse when the positron annihilates on opposite sides of the sample to be measured, thereby obtaining a first lifetime value and a second lifetime value; and then, by performing two-dimensional statistics on the first lifetime values ​​and the second lifetime values ​​that meet preset recording conditions, a large number of background counts can be effectively eliminated, the peak-to-valley ratio of the spectrum can be further improved, and the annihilation gamma photon information can be fully utilized to further improve the time resolution, thereby effectively improving the spectrum measurement accuracy.

[0072] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0073] Figure 3 This figure illustrates a flow chart of a two-dimensional positron annihilation lifetime spectrum measurement method according to an embodiment of the present disclosure. This method is applied to a two-dimensional positron annihilation lifetime spectrum measurement system, which can be integrated into electronic devices such as laptops and desktop computers. The method includes steps 310 through 350.

[0074] Step 310: Detect the start time of the radiation source decaying to generate a first energy signal, and the energy threshold of the first energy signal is set according to the energy of the starting gamma photon generated by the radiation source decaying.

[0075] Among them, the measurement of positron annihilation lifetime spectrum is usually based on the β + Decay produces positrons, which are often used in measurements 22As a radioactive source, Na can release positrons with kinetic energy of 0 to 0.545 MeV. When the radioactive source decays and produces positrons, it will cascade to produce initial gamma photons. Therefore, the generation time of the initial gamma photons can be used as the starting time of the radioactive source decaying and producing positrons. Since the initial gamma photons released by the radioactive source decay have specific energies, such as 22 When Na releases a positron, it cascades to produce an initial gamma photon of 1.28 MeV. Therefore, the corresponding energy threshold can be set according to this specific energy, and the time when the first detected energy signal reaches the energy threshold is used as the generation time of the positron to obtain the starting time, which is used as the starting point of the positron annihilation lifetime statistics.

[0076] Step 320: Detect the first stop time of the second energy signal generated by the first side of the sample to be tested, and detect the second stop time of the third energy signal generated by the second side of the sample to be tested. The energy thresholds of the second energy signal and the third energy signal are set according to the energy of the annihilation gamma photons generated by positron annihilation, and the first side is opposite to the second side.

[0077] When a positron annihilates in a sample, it typically generates two annihilation gamma photons of specific energies in opposite directions. Therefore, a second energy signal and a third energy signal can be detected on the first and second sides of the sample, respectively. The first and second sides are opposite sides of the sample, and the energy thresholds of the second and third energy signals are set based on the energy of the annihilation gamma photons. The time when the detected second energy signal reaches the energy threshold is used as the generation time of an annihilation gamma photon, obtaining a first stop time. The time when the detected third energy signal reaches the energy threshold is used as the generation time of another annihilation gamma photon, obtaining a second stop time, which serves as the endpoint of the positron annihilation lifetime statistics.

[0078] Step 330: When the first stop time meets the first recording condition, calculate and obtain a first lifespan value according to the start time and the first stop time.

[0079] Among them, the annihilation lifetime of the positron is the time difference from the release of the positron by the decay of the radioactive source to the annihilation of the positron, and the start of the annihilation case is marked by the generation of the starting gamma photon, and the end is marked by the generation of the annihilation gamma photon. Therefore, the time difference from the start time to the first stop time can identify the annihilation lifetime of the positron. In the present disclosure, the first lifetime value of the positron can be obtained by calculating the time difference between the start time and the first stop time.

[0080] In the disclosed embodiments, after obtaining the start time, a first lifetime value can be calculated based on the start time and the first stop time, provided the first stop time meets a first recording condition. The first recording condition is used to filter the first stop time to reduce the introduction of erroneous events caused by interference from other signals. The first recording condition can be set based on the annihilation lifetime range of the positron or the known error range of the measuring instrument. If the first stop time does not meet the first recording condition, the counting process can proceed directly to the next annihilation event, or the data for the current start time, first stop time, and so on can be marked or discarded.

[0081] Step 340: When the second stop time meets the second recording condition, calculate and obtain a second lifespan value according to the start time and the second stop time.

[0082] The calculation of the second stop time, the second recording condition and the second life value may refer to the calculation of the first stop time, the first recording condition and the first life value in the aforementioned step 330 , and will not be described again to avoid repetition.

[0083] Because positron annihilation typically releases two annihilation gamma photons simultaneously and in opposite directions, the disclosed embodiments detect these two annihilation gamma photons separately, thereby obtaining two lifetime values, a first lifetime value and a second lifetime value, for the same annihilation event. During the measurement process, the calculation of each lifetime value must meet both the first and second recording conditions, respectively, to more fully utilize the annihilation gamma photon information.

[0084] Step 350: When the first lifetime value and the second lifetime value are obtained, two-dimensional statistics are performed on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum.

[0085] In steps 310-340, the present disclosure collects the first and second lifetime values ​​of the annihilation case, respectively, and performs two-dimensional statistics only when counts are obtained for both the first and second lifetime values, thereby obtaining a two-dimensional positron annihilation lifetime spectrum. If either the first or second lifetime value is not obtained, it can be assumed that the corresponding first or second stop time does not meet the recording conditions, and the count of the annihilation case may be incorrect. Therefore, statistics for this annihilation case are not collected. This eliminates a large number of background counts from the obtained two-dimensional positron annihilation lifetime spectrum, further improving the peak-to-valley ratio of the spectrum and ensuring measurement accuracy.

[0086] In a method embodiment of the present disclosure, the first recording condition includes a start time and a first stop time obtained within a first preset time window.

[0087] Because the annihilation lifetime of a positron is typically distributed within a certain range, in the embodiments of the present disclosure, a first preset time window is set in the first recording condition. This first preset time window is used to determine whether the acquisition start time and the first stop time are within the statistical range of the annihilation lifetime, thereby eliminating erroneous cases. Alternatively, the timing may be started upon obtaining the start time, and if the first stop time is obtained within the first preset time window, the first stop time is determined to meet the first recording condition. Alternatively, the start time and the first stop time may be continuously acquired, and if the time interval between the start time and the first stop time is less than the first time window, the first stop time is determined to meet the first recording condition. This disclosure does not impose any specific limitations on this.

[0088] In one method embodiment of the present disclosure, the first preset time window is 100 nanoseconds.

[0089] The first preset time window can be set to 100 nanoseconds, meaning that timing begins when the start time is obtained, and a determination is made as to whether the first stop time is obtained before 100 nanoseconds have accumulated. Alternatively, the start time and the first stop time are continuously collected, and a determination is made as to whether the time interval between the start time and the first stop time is less than or equal to 100 nanoseconds. In this disclosure, 100 nanoseconds is used for illustrative purposes only. Those skilled in the art may adjust the range of the first preset time window based on actual measurement conditions and application requirements, and this disclosure does not impose any specific limitations thereon.

[0090] In one method embodiment of the present disclosure, the second recording condition includes a start time and a second stop time obtained within a second preset time window.

[0091] In the embodiment of the present disclosure, the second recording condition and the second preset time window may correspond to the description of the first recording condition and the first preset time window, and will not be described again to avoid repetition.

[0092] In one method embodiment of the present disclosure, the second preset time window is 100 nanoseconds.

[0093] In the embodiment of the present disclosure, the second preset time window may correspond to the relevant description of the first preset time window mentioned above, and will not be described again here to avoid repetition.

[0094] Figure 4 The following is a flow chart illustrating a statistical two-dimensional positron annihilation lifetime spectrum in an embodiment of the present disclosure. In one embodiment of the present disclosure, Figure 4 As shown, step 340 specifically includes the following steps 441 to 442.

[0095] Step 441: When the first life value and the second life value are obtained, two-dimensional statistics are performed with the first life value as the horizontal axis and the second life value as the vertical axis.

[0096] If both the first and second lifetime values ​​are counted, they can be considered to correspond to the same annihilation case. In this case, two-dimensional statistics can be performed with the first lifetime value on the horizontal axis and the second lifetime value on the vertical axis. Because positron annihilation typically produces two annihilation gamma photons simultaneously and in opposite directions, the first and second lifetime values ​​of the same annihilation case are typically concentrated within a region with a slope of 1 in two-dimensional statistics. Therefore, using two-dimensional statistics, the recorded first and second lifetime values ​​can be further filtered to obtain counts of valid annihilation cases.

[0097] Step 442: When the difference between the first lifetime value and the second lifetime value is less than the preset time difference, obtain a two-dimensional positron annihilation lifetime spectrum according to the first lifetime value and the second lifetime value.

[0098] In the disclosed embodiments, the first and second lifetime values ​​from the two-dimensional statistics can be further filtered based on the difference to eliminate accidental background counts. In one-dimensional statistics of positron annihilation lifetimes, since only the lifetime value corresponding to one annihilation gamma photon is counted for each annihilation case, coincidences of initial gamma photons and annihilation gamma photons that occur by chance cannot be eliminated, resulting in the count including initial gamma photons and annihilation gamma photons from different annihilation cases, which are accidentally counted through coincidence selection. In contrast, in the disclosed embodiments, the first and second lifetime values ​​corresponding to two annihilation gamma photons are counted for each annihilation case. Since the first and second lifetime values ​​should theoretically be the same, they should differ within a certain range in actual measurements. Therefore, filtering based on whether the difference between the first and second lifetime values ​​of the same positron is less than a preset time difference can further eliminate accidental background counts in the spectrum, thereby further improving the peak-to-valley ratio and ensuring the accuracy of the spectrum measurement.

[0099] Among them, the preset time difference can be adjusted according to the measurement object, measurement conditions, measurement results, measurement requirements, etc. For example, in actual measurement, different preset time differences can be selected according to the type and state of the sample to be measured, the accuracy of the measurement system, the distribution of the first life value and the second life value in the area with a slope of 1 in two-dimensional statistics, etc.

[0100] Figure 5 The following is a schematic diagram of a two-dimensional positron annihilation lifetime spectrum according to an embodiment of the present disclosure. In the measurement, the first lifetime value is obtained through channel A (Channel A), and the second lifetime value is obtained through channel B (Channel B). The first lifetime value is the horizontal axis, the second lifetime value is the vertical axis, and different colors are used to represent the counts of lifetime values ​​of different sizes for two-dimensional statistics. Figure 5As shown in the figure, it can be seen that the first and second life values ​​are concentrated in the direction of the straight line with a slope of 1 in two-dimensional statistics. Therefore, the straight lines with a slope of 1 on the horizontal and vertical axes can be used to divide the areas where the first and second life values ​​are concentrated, excluding scattered and accidental background counts.

[0101] Among them, taking area 510 as an example, the preset time difference is expressed as the intercept of the boundary of area 510 on the horizontal axis and the vertical axis. Taking the track width of the horizontal axis and the vertical axis as 10 picoseconds and the preset time difference as 500 picoseconds as an example, the intercept of the two boundaries of area 510 on the horizontal axis and the vertical axis is 50 tracks, so that in area 510, only counts whose difference between the first lifetime value and the second lifetime value is less than 500 picoseconds are included.

[0102] In the embodiments of the present disclosure, 500 picoseconds is only used as an example. Those skilled in the art can adaptively select the preset time difference in actual measurement. For example, the preset time difference can be determined before measurement based on the type and properties of the sample to be measured, the accuracy of the measurement system, etc.; or after the first life value and the second life value are obtained by measurement, the preset time difference can be determined based on the distribution of the first life value and the second life value in two-dimensional statistics, the data volume of the measurement data, the accuracy requirements, etc. The present disclosure does not make any specific restrictions here.

[0103] In one embodiment of the method disclosed herein, the first stop time corresponds to a first time resolution, the second stop time corresponds to a second time resolution, and the ratio of the first time resolution to the second time resolution is less than

[0104] The ratio of the first time resolution to the second time resolution includes a first ratio of the first time resolution to the second time resolution, and a second ratio of the second time resolution to the first time resolution. And the second ratio is less than

[0105] Time resolution (TR) is an indicator that measures the ability to distinguish different events in the time dimension during the measurement process. It is also one of the important factors affecting the accuracy of positron annihilation lifetime spectrum measurement. The observed value of annihilation lifetime in the measurement can be expressed as the following formula (3):

[0106] T=τ+δ=τ+δ start +δ stop (3)

[0107] Where T is the measured annihilation lifetime, τ is the ideal annihilation lifetime, δ is the lifetime deviation caused by the system time resolution, and δ start is the starting time deviation caused by the starting time resolution, δ stopis the stop time deviation caused by the stop time resolution.

[0108] On this basis, the system time resolution TR is composed of the starting time resolution TR start and stop time resolution TR stop The time resolution function can be regarded as a single Gaussian function, and the system time resolution function can be expressed as the following formula (4):

[0109]

[0110] The initial time resolution function can be expressed as follows:

[0111]

[0112] The stopping time resolution function can be expressed as follows:

[0113]

[0114] Where σ is the standard deviation of the system time resolution function, σ start is the standard deviation of the initial time resolution function, σ stop is the standard deviation of the stop time resolution function. Then the time resolution of the system is TR=2.355σ, and the starting time resolution is TR start =2.355σ start , stop time resolution TR stop =2.3556 stop , and the system time resolution satisfies Therefore, the lifetime component of positron annihilation can be obtained by deconvolving the positron annihilation lifetime spectrum F(t) with the system time resolution function R(t).

[0115] In the disclosed embodiment, the first lifetime value T1 and the second lifetime value T2 are collected and statistically analyzed in two dimensions to obtain a two-dimensional positron annihilation lifetime spectrum. Ideally, if there is no time resolution in the measurement, the first lifetime value and the second lifetime value in the two-dimensional positron annihilation lifetime spectrum are all distributed on the straight line T2 = T1. However, if there is time resolution, the first lifetime value can be expressed as follows:

[0116] T1=τ+δ1=τ+δ start +δ stop1 (7)

[0117] The second lifespan value can be expressed as follows:

[0118] T2=τ+δ2=τ+δ start +δ stop2 (8)

[0119] On this basis, the annihilation lifetime τ of positrons can be expressed by the following formula (9):

[0120]

[0121] where δ stop1 is the lifetime deviation caused by the first time resolution TR corresponding to the first stopping time stop1 δ stop2 is the lifetime deviation caused by the second time resolution TR corresponding to the second stopping time stop2 δ start is the lifetime deviation caused by the starting time resolution TR start δ start δ stop1 and δ stop2 satisfy the Gaussian distribution. Then, the time resolution corresponding to the channel measuring the first lifetime value can be expressed by the following formula (10):

[0122]

[0123] The time resolution corresponding to the channel measuring the second lifetime value can be expressed by the following formula (11):

[0124]

[0125] Figure 6 illustrates a schematic diagram of the annihilation lifetime diagonalization process in an embodiment of the present disclosure. As shown in Figure 6 , in the two-dimensional positron annihilation lifetime spectrum, due to the influence of the time resolution, the annihilation lifetime τ is distributed in the elliptical region 610. Diagonalize the annihilation lifetime τ in the elliptical region 610, that is, take as the measured value of the annihilation lifetime, and its deviation is Then, the time resolution TR of the two-dimensional positron annihilation lifetime spectrum can be expressed by the following formula (12):

[0126]

[0127] On this basis, if TR < TR1 and TR < TR2 are satisfied, then there is the following formula (13):

[0128] and

[0129] As shown in formula (13), when the ratio of the first time resolution TR stop1 to the second time resolution TR stop2 is less than In this case, the time resolution TR of the two-dimensional positron annihilation lifetime spectrum is smaller than the time resolution TR1 corresponding to the channel measuring the first lifetime value, and also smaller than the time resolution TR2 corresponding to the channel measuring the second lifetime value, so that the measurement accuracy of the two-dimensional positron annihilation lifetime spectrum is further improved on the basis of any single-channel positron annihilation lifetime spectrum.

[0130] The present disclosure provides a two-dimensional positron annihilation lifetime spectrum measurement method, which detects the start time of a first energy signal generated by the decay of a radioactive source, the first stop time of a second energy signal generated by the first side of a sample to be tested, and the second stop time of a third energy signal generated by the second side of the sample to be tested, wherein the energy threshold of the first energy signal is set according to the energy of the starting gamma photon generated by the decay of the radioactive source, and the energy thresholds of the second energy signal and the third energy signal are set according to the energy of the annihilation gamma photon generated by positron annihilation, and the first side is opposite to the second side; when the acquisition of the first stop time meets the first recording condition, a first lifetime value is calculated according to the start time and the first stop time; when the acquisition of the second stop time meets the second recording condition, a second lifetime value is calculated according to the start time and the second stop time; and then two-dimensional statistics are performed on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum of positrons annihilated in the sample to be tested.

[0131] The disclosed two-dimensional positron annihilation lifetime spectrum measurement method detects two annihilation gamma photons generated by an annihilation event during the measurement process, obtains their respective first and second stop times, and then performs two-dimensional statistics on the lifetime of the annihilation event based on the first and second stop times. This method can effectively eliminate background counts in the measurement, reduce the occasional introduction of erroneous events, and further improve the peak-to-valley ratio. Furthermore, it can improve the utilization rate of annihilation gamma photon information, thereby enhancing the temporal resolution of the measurement. This method effectively improves the measurement accuracy of the positron annihilation lifetime by improving the peak-to-valley ratio and temporal resolution.

[0132] The following are examples of the disclosed system, which can be used to implement the disclosed method examples. For details not disclosed in the disclosed device system examples, please refer to the disclosed method examples.

[0133] Figure 7 One of the structural diagrams of a two-dimensional positron annihilation lifetime spectrum measurement system 700 in an embodiment of the present disclosure is illustrated. Figure 7 The system may include:

[0134] The start time recording module 710 is used to detect the start time of the radiation source decaying to generate the first energy signal. The energy threshold of the first energy signal is set according to the energy of the starting gamma photon generated by the radiation source decaying.

[0135] The first stop time recording module 720 is used to detect the first stop time when the first side of the sample to be tested generates the second energy signal. The energy threshold of the second energy signal is set according to the energy of the annihilation gamma photon generated by positron annihilation.

[0136] The second stop time recording module 730 is used to detect the second stop time when the second side of the sample to be tested generates a third energy signal. The energy threshold of the third energy signal is set according to the energy of the annihilation gamma photon generated by positron annihilation, and the first side is opposite to the second side.

[0137] The life value calculation module 740 is configured to obtain a first life value by calculating the first life value according to the start time and the first stop time when the first stop time meets the first recording condition.

[0138] The life value calculation module 740 is further configured to obtain a second life value by calculation based on the start time and the second stop time when the second stop time meets the second recording condition.

[0139] The two-dimensional lifetime spectrum statistics module 750 is used to perform two-dimensional statistics on the first lifetime value and the second lifetime value when the first lifetime value and the second lifetime value are obtained, so as to obtain a two-dimensional positron annihilation lifetime spectrum.

[0140] The present disclosure provides a two-dimensional positron annihilation lifetime spectrum measurement system, which detects the start time of a first energy signal generated by the decay of a radioactive source, the first stop time of a second energy signal generated by the first side of a sample to be tested, and the second stop time of a third energy signal generated by the second side of the sample to be tested, wherein the energy threshold of the first energy signal is set according to the energy of the starting gamma photon generated by the decay of the radioactive source, and the energy thresholds of the second energy signal and the third energy signal are set according to the energy of the annihilation gamma photon generated by positron annihilation, and the first side is opposite to the second side; when the acquisition of the first stop time meets the first recording condition, the first lifetime value is calculated according to the start time and the first stop time; when the acquisition of the second stop time meets the second recording condition, the second lifetime value is calculated according to the start time and the second stop time; and then two-dimensional statistics are performed on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum of positrons annihilated in the sample to be tested.

[0141] The two-dimensional positron annihilation lifetime spectrum measurement system provided by the present disclosure detects two annihilation gamma photons generated by an annihilation event during the measurement process, obtains their respective first and second stop times, and then performs two-dimensional statistics on the lifetime of the annihilation event based on the first and second stop times. This effectively eliminates background counts in the measurement, reduces the occasional introduction of erroneous events, and further improves the peak-to-valley ratio. Furthermore, it improves the utilization rate of annihilation gamma photon information, thereby enhancing the temporal resolution of the measurement. This system effectively improves the measurement accuracy of positron annihilation lifetimes by improving both the peak-to-valley ratio and temporal resolution.

[0142] Figure 8 The second structural diagram of a two-dimensional positron annihilation lifetime spectrum measurement system 800 in the embodiment of the present disclosure is illustrated. Figure 8 As shown, the system may include a start time recording module 810, a first stop time recording module 820, a second stop time recording module 830, a life value calculation module 840 and a two-dimensional life spectrum statistics module 850;

[0143] In a system implementation of the present disclosure, the first stop time recording module 820 includes:

[0144] A first stop detector 821 is used to detect a second energy signal on a first side of the sample to be tested;

[0145] The first time extraction unit 822 is configured to extract the occurrence time of the second energy signal to obtain a first stop time when the second energy signal reaches 0.511 MeV.

[0146] In a system implementation of the present disclosure, the second stop time recording module 830 includes:

[0147] A second stop detector 831 is used to detect a third energy signal on the second side of the sample to be tested;

[0148] The second time extraction unit 832 is configured to extract the occurrence time of the third energy signal to obtain a second stop time when the third energy signal reaches 0.511 MeV.

[0149] Among them, the first stop detector 821 and the second stop detector 831 are set on the opposite sides of the sample to be tested, for example, they can be arranged in opposite directions at an angle of 180° on both sides of the sample to be tested, so as to respectively detect the two annihilation gamma photons generated in opposite directions and simultaneously after the annihilation of the positron in the sample to be tested.

[0150] In a system embodiment of the present disclosure, the first stop time recording module 820 corresponds to a first time resolution, the second stop time recording module 830 corresponds to a second time resolution, and the ratio of the first time resolution to the second time resolution is less than √3.

[0151] In one system embodiment of the present disclosure, the two-dimensional life spectrum statistics module 850 includes:

[0152] A life value statistics unit 851 is configured to perform two-dimensional statistics with the first life value as the horizontal axis and the second life value as the vertical axis when the first life value and the second life value are obtained;

[0153] The lifetime value extraction unit 852 is used to obtain a two-dimensional positron annihilation lifetime spectrum according to the first lifetime value and the second lifetime value when the difference between the first lifetime value and the second lifetime value is less than a preset time difference.

[0154] In a system embodiment of the present disclosure, the first recording condition includes a start time and a first stop time obtained within a first preset time window.

[0155] In a system embodiment of the present disclosure, the second recording condition includes a start time and a second stop time obtained within a second preset time window.

[0156] In a system implementation of the present disclosure, the start time recording module 810 includes:

[0157] A starting detector 811 is used to detect a first energy signal of a radiation source;

[0158] The third time extraction unit 812 is configured to extract the occurrence time of the first energy signal to obtain the start time when the first energy signal reaches 1.28 MeV.

[0159] In one system embodiment of the present disclosure, the life value calculation module 840 includes:

[0160] A first time difference calculation unit 841 is configured to calculate a first lifespan value based on the start time and the first stop time when the first stop time meets the first recording condition;

[0161] The second time difference calculation unit 842 is configured to obtain a second lifespan value by calculation based on the start time and the second stop time when the second stop time meets the second recording condition.

[0162] It should be noted that although several modules or units of the device for action execution are mentioned in the detailed description above, this division is not mandatory. In fact, according to the embodiments of the present disclosure, the features and functions of two or more modules or units described above can be concretized in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided into multiple modules or units to be concretized.

[0163] Furthermore, although the steps of the method of the present disclosure are described in a particular order in the accompanying drawings, this does not require or imply that the steps must be performed in this particular order, or that all steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps.

[0164] Through the description of the above embodiments, it is easy for those skilled in the art to understand that the example embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which can be a personal computer, a server, a mobile terminal, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.

[0165] In an exemplary embodiment of the present disclosure, an electronic device capable of implementing the above method is also provided.

[0166] Those skilled in the art will appreciate that various aspects of the present disclosure may be implemented as systems, methods, or program products. Therefore, various aspects of the present disclosure may be implemented in the following forms: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits," "modules," or "systems."

[0167] Refer to the following Figure 9 hereinafter, an electronic device 900 according to this embodiment of the present disclosure is described. Figure 9 The electronic device 900 shown is merely an example and should not limit the functions and scope of use of the embodiments of the present disclosure.

[0168] like Figure 9 As shown, electronic device 900 is implemented as a general-purpose computing device. Components of electronic device 900 may include, but are not limited to, at least one processing unit 910, at least one storage unit 920, and a bus 930 connecting various system components (including storage unit 920 and processing unit 910).

[0169] The storage unit stores program codes, which can be executed by the processing unit 910, so that the processing unit 910 executes the steps according to various exemplary embodiments of the present disclosure described in the above “Exemplary Method” section of this specification.

[0170] The storage unit 920 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 9201 and / or a cache memory unit 9202 , and may further include a read-only memory unit (ROM) 9203 .

[0171] The storage unit 920 may also include a program / utility 9204 having a set (at least one) of program modules 9205, such program modules 9205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0172] Bus 930 may represent one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0173] The electronic device 900 can also communicate with one or more external devices (e.g., a keyboard, a pointing device, a Bluetooth device, etc.), one or more devices that enable a user to interact with the electronic device 900, and / or any device that enables the electronic device 900 to communicate with one or more other computing devices (e.g., a router, a modem, etc.). Such communication can occur via a display unit 940 and an input / output (I / O) interface 950 connected to the display unit 940. Furthermore, the electronic device 900 can also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network such as the Internet) via a network adapter 960. As shown, the network adapter 960 communicates with other modules of the electronic device 900 via a bus 930. It should be understood that, although not shown in the figure, other hardware and / or software modules can be used in conjunction with the electronic device 900, including but not limited to microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0174] Through the description of the above embodiments, it is easy for those skilled in the art to understand that the example embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which can be a personal computer, a server, a terminal device, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.

[0175] In exemplary embodiments of the present disclosure, a computer-readable storage medium is also provided, on which is stored a program product capable of implementing the aforementioned methods of this specification. In some possible implementations, various aspects of the present disclosure may also be implemented in the form of a program product comprising program code. When the program product is executed on a terminal device, the program code is configured to cause the terminal device to execute the steps described in the "Exemplary Methods" section of this specification according to various exemplary embodiments of the present disclosure.

[0176] In an embodiment of the present disclosure, a program product for implementing the above-mentioned method is also provided. The program product may be a portable compact disc read-only memory (CD-ROM) and includes program code, and can be run on a terminal device, such as a personal computer. However, the program product of the present disclosure is not limited thereto. In this document, a readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0177] The program product may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or component, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0178] A computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, which carries readable program code. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium that can transmit, propagate, or transfer a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0179] The program code embodied on the readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0180] Program code for performing the operations of the present disclosure may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, and the like, as well as conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a stand-alone software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving a remote computing device, the remote computing device may be connected to the user computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0181] Furthermore, the figures above are merely illustrative of the processes included in the methods according to exemplary embodiments of the present disclosure and are not intended to be limiting. It is readily understood that the processes illustrated in the figures above do not indicate or limit the temporal order of these processes. Furthermore, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0182] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow from the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the claims.

Claims

1. A two-dimensional positron annihilation lifetime spectrum measurement method, characterized in that: The method comprises: Detecting the start time of a first energy signal generated by decay of a radioactive source, wherein an energy threshold of the first energy signal is set according to the energy of an initial gamma photon generated by decay of the radioactive source; detecting a first stop time of generating a second energy signal on a first side of the sample to be tested, and detecting a second stop time of generating a third energy signal on a second side of the sample to be tested, wherein energy thresholds of the second energy signal and the third energy signal are set according to the energy of annihilation gamma photons generated by positron annihilation, and the first side is opposite to the second side; When the first stop time meets the first recording condition, a first life value is calculated according to the start time and the first stop time; When the second stop time meets the second recording condition, a second lifespan value is calculated based on the start time and the second stop time; When the first lifetime value and the second lifetime value are obtained, performing two-dimensional statistics on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum; The first recording condition includes: The start time and the first stop time are obtained within a first preset time window; The second recording condition includes: The start time and the second stop time are obtained within a second preset time window; The method further comprises: In the two-dimensional positron annihilation lifetime spectrum, the areas where the first lifetime values ​​and the second lifetime values ​​are concentrated are divided by straight lines with a slope of 1 on the horizontal axis and the vertical axis; A diagonalization process is performed in the region where the first lifetime values ​​and the second lifetime values ​​are concentratedly distributed to obtain a measured value of the annihilation lifetime.

2. The method according to claim 1, characterized in that The method of performing two-dimensional statistics on the first lifetime value and the second lifetime value to obtain a two-dimensional positron annihilation lifetime spectrum after obtaining the first lifetime value and the second lifetime value includes: When the first life value and the second life value are obtained, two-dimensional statistics are performed with the first life value on the horizontal axis and the second life value on the vertical axis; When the difference between the first lifetime value and the second lifetime value is smaller than a preset time difference, the two-dimensional positron annihilation lifetime spectrum is obtained according to the first lifetime value and the second lifetime value.

3. The method according to claim 1, characterized in that The first stop time corresponds to a first time resolution, the second stop time corresponds to a second time resolution, and the ratio of the first time resolution to the second time resolution is less than 4. A two-dimensional positron annihilation lifetime spectrum measurement system, characterized in that: The system comprises: a start time recording module, configured to detect the start time of a first energy signal generated by decay of a radioactive source, wherein an energy threshold of the first energy signal is set according to the energy of a starting gamma photon generated by decay of the radioactive source; a first stop time recording module, configured to detect a first stop time when a second energy signal is generated on a first side of the sample to be tested, wherein an energy threshold of the second energy signal is set according to an energy of an annihilation gamma photon generated by positron annihilation; a second stop time recording module, configured to detect a second stop time when a third energy signal is generated on a second side of the sample to be tested, wherein an energy threshold of the third energy signal is set according to an energy of an annihilation gamma photon generated by positron annihilation, and the first side is opposite to the second side; a life value calculation module, configured to calculate a first life value based on the start time and the first stop time when the first stop time meets a first recording condition; The life value calculation module is further configured to calculate a second life value based on the start time and the second stop time when the second stop time meets a second recording condition; a two-dimensional lifetime spectrum statistics module, configured to perform two-dimensional statistics on the first lifetime value and the second lifetime value when the first lifetime value and the second lifetime value are obtained, so as to obtain a two-dimensional positron annihilation lifetime spectrum; The first recording condition includes: The start time and the first stop time are obtained within a first preset time window; The second recording condition includes: The start time and the second stop time are obtained within a second preset time window; The two-dimensional lifetime spectrum statistics module is also used to divide the area where the first lifetime value and the second lifetime value are concentrated in the two-dimensional positron annihilation lifetime spectrum by straight lines with a slope of 1 on the horizontal axis and the vertical axis; perform diagonal processing in the area where the first lifetime value and the second lifetime value are concentrated to obtain the measured value of the annihilation lifetime.

5. The system according to claim 4, characterized in that The first stop time recording module includes: a first stop detector, configured to detect a second energy signal on the first side of the sample to be tested; a first time extraction unit, configured to extract the occurrence time of the second energy signal to obtain a first stop time when the second energy signal reaches 0.511 MeV; The second stop time recording module includes: a second stop detector, configured to detect a third energy signal on the second side of the sample to be tested; The second time extraction unit is configured to extract the occurrence time of the third energy signal to obtain a second stop time when the third energy signal reaches 0.511 MeV.

6. The system according to claim 4, characterized in that The first stop time recording module corresponds to a first time resolution, the second stop time recording module corresponds to a second time resolution, and the ratio of the first time resolution to the second time resolution is less than 7. The system according to claim 4, wherein: The two-dimensional life spectrum statistics module includes: A life value statistics unit is configured to perform two-dimensional statistics with the first life value as the horizontal axis and the second life value as the vertical axis when the first life value and the second life value are obtained; The lifetime value extraction unit is configured to obtain the two-dimensional positron annihilation lifetime spectrum according to the first lifetime value and the second lifetime value when the difference between the first lifetime value and the second lifetime value is less than a preset time difference.

8. The system according to claim 4, wherein: The start time recording module includes: a starting detector, configured to detect the first energy signal from the radiation source; The third time extraction unit is configured to extract the occurrence time of the first energy signal to obtain a start time when the first energy signal reaches 1.28 MeV.

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