CN111487667B - Positron annihilation angle correlation measuring device - Google Patents
Positron annihilation angle correlation measuring device Download PDFInfo
- Publication number
- CN111487667B CN111487667B CN202010387948.2A CN202010387948A CN111487667B CN 111487667 B CN111487667 B CN 111487667B CN 202010387948 A CN202010387948 A CN 202010387948A CN 111487667 B CN111487667 B CN 111487667B
- Authority
- CN
- China
- Prior art keywords
- logic
- coincidence
- strip
- fixed detector
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
- G01T1/362—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry with scintillation detectors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
- G01T1/361—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry with a combination of detectors of different types, e.g. anti-Compton spectrometers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
- G01T1/366—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry with semi-conductor detectors
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- High Energy & Nuclear Physics (AREA)
- Molecular Biology (AREA)
- Measurement Of Radiation (AREA)
Abstract
The invention relates to a positron annihilation angle correlation measurement device, belongs to the technical field of nuclear detection, and solves the problems of low feasibility, large counting loss, long measurement time and low efficiency in the prior art. The device comprises a first fixed detector, a second fixed detector and a coincidence system; the first fixed detector and the second fixed detector are respectively arranged on two sides of the sample in parallel and symmetrically; the multiple first strip-shaped detection units and the multiple second strip-shaped detection units of the first fixed detector and the second fixed detector are respectively used for detecting incident position information of first gamma photons and second gamma photons which are generated by annihilation of electrons and positrons and propagate along the reverse direction in the sample; and the coincidence system is used for acquiring incident position information of the first gamma photon and the second gamma photon within coincidence time, and acquiring a one-dimensional positron annihilation angle correlation spectrum according to the incident position information and the position information of the sample. The method is simple to operate, high in measurement efficiency and capable of improving measurement resolution.
Description
Technical Field
The invention relates to the technical field of nuclear detection, in particular to a positron annihilation angle correlation measuring device.
Background
One-dimensional positron annihilation angle correlation experiment is a basic experimental means in positron annihilation technology. The device can directly provide the momentum density distribution of annihilation photon pairs, the distribution has a definite relation with the electron momentum distribution in the solid, and an experimentally measured angle correlation curve can reflect the density distribution of electrons detected by positrons in a momentum space, so that the device is used for measuring Fermi surfaces in metals and alloys and researching the electron momentum distribution and defects of various solid materials. Compared with other traditional methods, the angle correlation method does not require extreme conditions such as ultra-pure samples, ultralow temperature, strong magnetic fields and the like and microwave technology, so that the method is widely applied to the fields of physics, chemistry, biology and the like.
Angle correlation spectrometers are precision instruments that measure the angular distribution of annihilation radiation. The traditional angle correlation measuring device comprises a fixed detector matched with a fixed collimator and a movable detector matched with a rotatable collimator, measurement needs to be carried out under different deflection angles for many times, and because the deflection angle is very small, in order to guarantee high resolution and enough counting rate, the distance between the detector and a sample is required to be far, and a strong positive electron source is also required to be used.
The prior art has at least the following disadvantages, namely, in order to improve the angular resolution, the detector is usually far away from the sample; secondly, the collimator causes a large amount of counting loss, and angle measurement statistics one by one causes longer measuring time and low measuring efficiency.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a positron annihilation angle correlation measurement apparatus, which solves the problems of low feasibility, large counting loss, long measurement time, low efficiency and low angular resolution of the conventional measurement apparatus.
The invention provides a positron annihilation angle correlation measurement device which comprises a first fixed detector, a second fixed detector and a coincidence system, wherein the first fixed detector is connected with the second fixed detector;
the first fixed detector comprises a plurality of first strip-shaped detection units, and the second fixed detector comprises a plurality of second strip-shaped detection units;
the first fixed detector and the second fixed detector are respectively arranged on two sides of the sample in parallel and symmetrically; the first strip-shaped detection units and the second strip-shaped detection units are respectively used for detecting incident position information of first gamma photons and second gamma photons which are generated by annihilation of electrons and positrons and propagate along the reverse direction in a sample;
the coincidence system is used for acquiring incident position information of a first gamma photon and a second gamma photon within coincidence time, acquiring a corresponding annihilation angle according to the incident position information and the position information of the sample, and acquiring a one-dimensional positron annihilation angle correlation spectrum according to the annihilation angle.
Furthermore, the first strip-shaped detection units and the second strip-shaped detection units are arranged in a one-dimensional array.
Further, the first strip-shaped detection unit and the second strip-shaped detection unit both comprise strip-shaped scintillators and photomultiplier tube modules coupled with the strip-shaped scintillators;
the bar-shaped scintillator is used for converting the first or second gamma photons into a first or second optical signal;
the photomultiplier module is used for converting the first or second optical signal into a first or second electrical signal, and the first or second electrical signal contains incident position information of the first gamma photon or the second gamma photon.
Further, an optical isolation layer is arranged between any two adjacent strip-shaped scintillators in the first fixed detector and the second fixed detector.
Furthermore, each first strip detecting unit and each second strip detecting unit transmit the first electric signal or the second electric signal to the coincidence system through a separate coding signal channel.
Furthermore, the coincidence system comprises a digital waveform processing module, a logic conversion module, a time coincidence judgment module and a logic coincidence judgment module;
the digital waveform processing module is used for converting the first electric signal and the second electric signal into a first digital signal and a second digital signal respectively;
the logic conversion module is used for comparing each first digital signal with a threshold value to generate a first group of logic values; also for comparing each of the second digital signals to a threshold to generate a second set of logic values;
the time coincidence judgment module is used for judging the time coincidence of the first digital signal and the second digital signal;
the logic coincidence judgment module is used for carrying out logic coincidence judgment on the first group of logic values and the second group of logic values;
and the processor is used for obtaining a corresponding annihilation angle according to the first group of logic values and the second group of logic values under the condition of meeting time coincidence and logic coincidence, and obtaining a one-dimensional positron annihilation angle correlation spectrum according to the annihilation angle.
Further, the time coincidence judgment module judges the time coincidence by the following method:
comparing the digital signal with a threshold value, and triggering a clock signal if the digital signal is greater than or equal to the threshold value; if the clock signals triggered by the first digital signal and the second digital signal are both in a preset time window, the time is satisfied, otherwise, the time is not satisfied;
the first group of logic values are the logic value combinations output by each coding signal channel of the first fixed detector, and the second group of logic values are the logic value combinations output by each coding signal channel of the second fixed detector; if the first or second digital signal is greater than or equal to the threshold value, the output of the corresponding coding signal channel is 1, otherwise, the output is 0;
the logic coincidence judgment module carries out logic coincidence judgment in the following way:
and if both the first group of logic values and the second group of logic values have one logic value of 1 and the other logic values are 0, the logic is satisfied, otherwise, the logic is not satisfied.
Further, the processor executes the following process to obtain the corresponding annihilation angle:
under the condition of meeting time coincidence and logic coincidence, determining the position of a first strip-shaped detection unit for receiving a first gamma photon and the position of a second strip-shaped detection unit for receiving a second gamma photon according to an encoding signal channel with an output of 1 in the first group of logic values and an encoding signal channel with an output of 1 in the second group of logic values so as to obtain the incident position coordinate of the first gamma photon and the incident position coordinate of the second gamma photon;
and obtaining a corresponding annihilation angle theta according to the incident position coordinate and the position coordinate of the sample.
Further, the processor is further configured to count and count annihilation angle θ values within a preset time period to obtain a distribution of θ values, so as to obtain a one-dimensional positron annihilation angle correlation spectrum.
Further, the angular resolution of the measuring device is
Wherein a is the width of each detection unit, and L is the distance between the sample and the first and second fixed detectors.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
1. incident position information of two gamma photons is obtained by using a fixed detector with position resolution capability, and a corresponding annihilation angle is obtained according to the incident position information and the position information of the sample, so that the problem of the limitation of angle correlation measurement by using collimator equipment is solved, the counting loss caused by a collimation slit is avoided, and the measurement accuracy is improved.
2. The fixed detector with the position resolution capability is a strip array detector, the structure is simple, a traditional measuring device for measuring by using a collimator and a movable detector to scan angles is completely abandoned, the operation is simplified, the measuring efficiency is improved in multiples, and the feasibility is improved.
3. The angle resolution of the positron annihilation angle correlation measurement device is related to the width of the strip-shaped detection unit and the distance between the detector and the sample, so that the angle resolution can be adjusted by adjusting the width of the strip-shaped detection unit and the distance between the detector and the sample.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic diagram of a conventional one-dimensional positron annihilation angle correlation measurement apparatus;
FIG. 2 is a schematic diagram of a positron annihilation angle correlation measurement apparatus according to an embodiment of the invention;
FIG. 3 is a schematic diagram of the positioning and positioning of the fixed detectors according to the embodiment of the present invention;
FIG. 4 is a schematic diagram of a bar scintillator coupled to a photomultiplier tube according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a system in accordance with an embodiment of the present invention.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
To better demonstrate the outstanding substantive features and significant advances of the positron annihilation angle correlation measurement apparatus of the present invention over existing measurement apparatuses, a detailed description of an existing measurement apparatus is now provided, as shown in figure 1.
In the prior art, a one-dimensional positron annihilation angle correlation measurement device is realized by measuring coincidence gamma photon (gamma) counts under different theta off-angles. Taking a sample as an axis, respectively placing a detector at two sides, wherein the front end of the detector is provided with a long and narrow collimator, and the detector can only detect gamma photons passing through a slit of the collimator and count the gamma photons; and one of the detectors is fixed, the other detector and the collimator at the front end are driven by the rotating arm to rotate around the sample, and the detector stays at different theta angles and records coincidence counting. Since the momentum of an annihilation pair is much less than the momentum of an annihilation photon, theta is usually very small (theta <1 deg.), and to ensure high resolution and sufficient count rate, the detector is very distant, up to several meters, from the positron source and sample, and a much higher source of strong positron electrons (50 mCi-1 Ci) must be used than is used for lifetime spectroscopy and extended energy spectroscopy measurements. Therefore, the detector is usually far from the sample, the collimating slit causes a large number of counting losses, and the measurement time is long due to the counting of angle-by-angle, the efficiency is low, and the like, which results in low feasibility of the device.
The device is further improved in the prior art, and specifically, a fixed detector and a fixed collimator at one end are kept unchanged, a rotatable collimator and a movable detector are replaced by another fixed detector, the other fixed detector comprises a plurality of crystal strips linearly arranged along the slit direction, and different crystal strips correspond to different included angles theta, so that angle scanning is avoided. Firstly, the scintillation light generated by the crystal bar needs to be modulated, and the modulated scintillation light is arranged along the direction of the slit in sequence, so that the operation is complex, and the modulated scintillation light is easy to generate positioning deviation and error; secondly, the slit structure among a plurality of crystal strips still causes a large amount of counting loss, and the fixed detector and the fixed collimator at one end without any improvement still have the defect of counting loss caused by the collimator slit, and the detection precision is low. It can be seen that the prior art and improvements are directed to improvements in the apparatus at one end of the movable probe.
In order to overcome the defects of the existing measuring device, a specific embodiment of the invention discloses a positron annihilation angle correlation measuring device based on a position resolution detector. As shown in fig. 2, comprises a first fixed detector, a second fixed detector and a coincidence system;
the first fixed detector comprises a plurality of first strip-shaped detection units, and the second fixed detector comprises a plurality of second strip-shaped detection units; the number of the strip-shaped detection units can be determined according to the specific requirement of the angular resolution;
the first fixed detector and the second fixed detector are respectively arranged on two sides of the sample in parallel and symmetrically; the first strip-shaped detection units and the second strip-shaped detection units are respectively used for detecting incident position information of first gamma photons and second gamma photons which are generated by annihilation of electrons and positrons and propagate along the reverse direction in the sample; specifically, a positive electron source irradiates a sample, and annihilates with electrons in the sample to generate two characteristic gamma photons (annihilation photon pair), i.e., a first gamma photon and a second gamma photon, which propagate in opposite directions;
the coincidence system is used for collecting incident position information of a first gamma photon and a second gamma photon within coincidence time, obtaining a corresponding annihilation angle according to the incident position information and the position information of the sample, and obtaining a one-dimensional positron annihilation angle correlation spectrum according to the annihilation angle.
Incident position information of the first gamma photon and the second gamma photon in the coincidence time is collected, so that the collected position information is the incident position information of the first gamma photon and the second gamma photon corresponding to the annihilation photon pair.
Preferably, the plurality of first strip-shaped detection units and the plurality of second strip-shaped detection units are arranged in a one-dimensional array.
Exemplarily, the placement positions of the first fixed detector and the second fixed detector and the arrangement manner of the strip-shaped detection units are shown in fig. 3, wherein fig. 3(a), (b), and (c) are respectively a perspective view, an xy-perspective view, and a yz-perspective view; fig. 3 shows only one of the cases, and in practical applications, the placement positions and the placement modes of the first fixed detector and the second fixed detector are only parallel and symmetrical with respect to the sample position.
Preferably, as shown in fig. 4, each of the first and second strip-shaped detection units includes a strip-shaped scintillator and a photomultiplier tube module coupled to the strip-shaped scintillator;
the bar-shaped scintillator is used for converting the first or second gamma photons into a first or second optical signal; the strip-shaped scintillator can sense a single gamma photon of 0.511Mev, so that the detection precision is improved;
the photomultiplier module is used for converting the first or second optical signal into a first or second electrical signal, and the first or second electrical signal contains incident position information of the first gamma photon or the second gamma photon. Specifically, the light emission spectrum of the strip-shaped scintillator is matched with the absorption spectrum of the photomultiplier tube module, and preferably, the strip-shaped scintillator adopts yttrium lutetium silicate scintillation crystal (LYSO), so that the physical and chemical properties of the strip-shaped scintillator are stable, and the detection efficiency of gamma rays is high; the photomultiplier module adopts a silicon photomultiplier module (SiPM module); for example, 8-by-8 silicon photomultiplier modules arranged in an array can be adopted, each strip-shaped scintillator is coupled with a row of 8 silicon photomultiplier modules to form a detection unit, and even if the strip-shaped scintillators are tightly attached to the silicon photomultiplier modules, optical signal leakage cannot occur.
In consideration of the fact that the position of each detection unit corresponds to the incident position information of gamma photons one to one, in order to prevent a first gamma photon or a second gamma photon detected by any one bar-shaped scintillator from being detected by other bar-shaped scintillators, an optical isolation layer is arranged between any two adjacent bar-shaped scintillators in the first fixed detector and the second fixed detector.
In order to distinguish the incident position of the first gamma photon or the second gamma photon, each of the first strip detection units and each of the second strip detection units transmit the first electrical signal or the second electrical signal to the coincidence system through a separate encoded signal channel.
Preferably, as shown in fig. 5, the coincidence system includes a high-speed analog sampling module, a digitized waveform processing module, a logic conversion module, a multi-channel data transmission module, a cache module, a time coincidence determination module, a logic coincidence determination module, and a processor;
the high-speed analog sampling module is used for respectively acquiring the first electric signal and the second electric signal;
the digital waveform processing module is used for respectively converting the first electric signal and the second electric signal into a first digital signal and a second digital signal, storing the first digital signal and a corresponding signal channel code, the second digital signal and a corresponding signal channel code into a first-level cache unit of the cache module, and simultaneously transmitting the first digital signal and the second digital signal to the time coincidence judgment module for time coincidence judgment;
the multi-channel communication module is used for respectively packaging the first digital signal and the corresponding signal channel code as well as the second digital signal and the corresponding signal channel code into a first data packet and a second data packet, and transmitting the first data packet and the second data packet to the logic conversion module;
the logic conversion module is configured to compare each digital signal in the first data packet with a threshold, output 1 by the corresponding encoded signal channel if the digital signal is greater than or equal to the threshold, output 0 by the corresponding encoded signal channel if the digital signal is less than the threshold, generate a first set of logic values, compare each digital signal encoded by each signal channel in the second data packet with the threshold, generate a second set of logic values, and store the first set of logic values and the second set of logic values in a second-level cache unit of the cache module;
wherein the first electrical signal and the second electrical signal contain intensity information of the first gamma photon and the second gamma photon, respectively, and thus the threshold is determined according to the amplitude of the electrical signal corresponding to the gamma photon. A threshold value or greater indicates that the channel receives a gamma photon, and the channel outputs a 1.
And the logic coincidence judgment module is used for carrying out logic coincidence judgment on the first group of logic values and the second group of logic values.
And the processor is used for obtaining corresponding annihilation angles according to the first group of logic values and the second group of logic values under the condition of meeting time coincidence and logic coincidence, and obtaining a one-dimensional positron annihilation angle correlation spectrum according to the annihilation angles.
Preferably, the time coincidence judging module judges the time coincidence by the following method:
comparing the digital signal with a threshold value, and triggering a clock signal if the digital signal is greater than or equal to the threshold value; if the clock signals triggered by the first digital signal and the second digital signal are both in a preset time window, the time is satisfied, otherwise, the time is not satisfied;
the first group of logic values are the logic value combinations output by each coding signal channel of the first fixed detector, and the second group of logic values are the logic value combinations output by each coding signal channel of the second fixed detector; if the first or second digital signal is greater than or equal to the threshold value, the output of the corresponding coding signal channel is 1, otherwise, the output is 0;
the logic coincidence judgment module carries out logic coincidence judgment in the following way:
and if both the first group of logic values and the second group of logic values have one logic value of 1 and the other logic values have 0, the logic is satisfied, otherwise, the logic is not satisfied. Wherein both the first and second sets of logical values and only one logical value is 1, indicating that both the first and second fixed detectors detect only one gamma photon, logically belonging to a valid event.
Preferably, the processor executes the following process to obtain the corresponding annihilation angle:
under the condition of meeting the time coincidence and the logic coincidence, determining the position of a first strip-shaped detection unit receiving the first gamma photon and the position of a second strip-shaped detection unit receiving the second gamma photon according to the coded signal channel with the output of 1 in the first group of logic values and the coded signal channel with the output of 1 in the second group of logic values to obtain the incident position coordinate A of the first gamma photon 1 And the incident position coordinate A of the second gamma photon 2 (ii) a Considering that the first strip-shaped detection unit and the second strip-shaped detection unit are micro strip-shaped devices, the central position coordinates of the strip-shaped detection unit corresponding to the coded signal channel with the output of 1 are used as the incident position coordinates of the gamma photons.
Obtaining a corresponding annihilation angle theta according to the incident position coordinate and the position coordinate O of the sample by the following formula:
preferably, the processor is further configured to count and count annihilation angle θ values within a preset time period to obtain a distribution of θ values, so as to obtain a one-dimensional positron annihilation angle correlation spectrum.
Preferably, the angular resolution of the measuring device is
Wherein a is the width of each detecting unit, and L is the distance between the sample and the first fixed detector and the second fixed detector, therefore, when the size of the first fixed detector and the second fixed detector is fixed, the angular resolution of the measuring device can be increased by increasing the number of the strip-shaped detecting units or decreasing the distance between the sample and the first fixed detector and the second fixed detector.
Compared with the prior art, the positron annihilation angle correlation measurement device provided by the invention has the advantages that firstly, the incident position information of two gamma photons is obtained by using the fixed detector with position resolution capability, and the corresponding annihilation angle is obtained according to the incident position information and the position information of the sample, so that the problem of angle correlation limitation by using collimator equipment is solved, the counting loss caused by a collimation slit is avoided, and the measurement accuracy is improved; secondly, the fixed detector with the position resolution capability is a strip array detector, the structure is simple, the traditional measuring device for measuring by using the scanning angle of a collimator and a movable detector is completely abandoned, the operation is simplified, the measuring efficiency is improved in multiples, and the feasibility is improved; finally, the angle resolution of the positron annihilation angle correlation measurement device provided by the invention is related to the width of the strip-shaped detection unit and the distance between the detector and the sample, so that the angle resolution can be adjusted by adjusting the width of the strip-shaped detection unit and the distance between the detector and the sample.
Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (6)
1. A positron annihilation angle correlation measurement device is characterized by comprising a first fixed detector, a second fixed detector and a coincidence system;
the first fixed detector comprises a plurality of first strip-shaped detection units, and the second fixed detector comprises a plurality of second strip-shaped detection units;
the first fixed detector and the second fixed detector are respectively arranged on two sides of the sample in parallel and symmetrically; the first strip-shaped detection units and the second strip-shaped detection units are respectively used for detecting incident position information of first gamma photons and second gamma photons which are generated by annihilation of electrons and positrons and propagate along the reverse direction in the sample; the position of each detection unit corresponds to the incident position information of the gamma photons one by one;
the coincidence system is used for acquiring incident position information of a first gamma photon and a second gamma photon within coincidence time, acquiring a corresponding annihilation angle according to the incident position information and the position information of the sample, and acquiring a one-dimensional positron annihilation angle correlation spectrum according to the annihilation angle;
the first strip-shaped detection unit and the second strip-shaped detection unit respectively comprise strip-shaped scintillators and a row of photomultiplier modules coupled with the strip-shaped scintillators, and a light isolation layer is arranged between any two adjacent strip-shaped scintillators in the first fixed detector and the second fixed detector;
the bar-shaped scintillator is used for converting the first or second gamma photons into a first or second optical signal;
the photomultiplier tube module is used for converting the first or second optical signal into a first or second electrical signal, and the first or second electrical signal contains incident position information of the first gamma photon or the second gamma photon;
the coincidence system comprises a digital waveform processing module, a logic conversion module, a time coincidence judgment module and a logic coincidence judgment module;
the digital waveform processing module is used for converting the first electric signal and the second electric signal into a first digital signal and a second digital signal respectively;
the logic conversion module is used for comparing each first digital signal with a threshold value to generate a first group of logic values; also for comparing each of the second digital signals to a threshold to generate a second set of logic values;
the time coincidence judgment module is used for judging time coincidence of the first digital signal and the second digital signal;
the logic coincidence judgment module is used for performing logic coincidence judgment on the first group of logic values and the second group of logic values; a processor, configured to obtain a corresponding annihilation angle according to the first and second sets of logical values and obtain a one-dimensional positron annihilation angle correlation spectrum according to the annihilation angle, if time coincidence and logical coincidence are satisfied;
the time coincidence judgment module judges the time coincidence by the following method:
comparing the digital signal with a threshold value, and triggering a clock signal if the digital signal is greater than or equal to the threshold value; if the clock signals triggered by the first digital signal and the second digital signal are both in a preset time window, the time is satisfied, otherwise, the time is not satisfied;
the first group of logic values are the logic value combinations output by each coding signal channel of the first fixed detector, and the second group of logic values are the logic value combinations output by each coding signal channel of the second fixed detector; if the first or second digital signal is greater than or equal to the threshold value, the output of the corresponding coding signal channel is 1, otherwise, the output is 0;
the logic coincidence judgment module carries out logic coincidence judgment in the following way:
and if both the first group of logic values and the second group of logic values have one logic value of 1 and the other logic values have 0, the logic is satisfied, otherwise, the logic is not satisfied.
2. The positron annihilation angle correlation measurement apparatus of claim 1, wherein the plurality of first and second strip-shaped detection units are each arranged in a one-dimensional array.
3. The positron annihilation angle correlation measurement apparatus of claim 2 wherein each of the first strip detector cells and each of the second strip detector cells transmit the first electrical signal or the second electrical signal to the coincidence system via a separate encoded signal channel.
4. The positron annihilation angle correlation measurement apparatus of claim 1 wherein the processor performs the following procedure to obtain the corresponding annihilation angle:
under the condition of meeting time coincidence and logic coincidence, determining the position of a first bar-shaped detection unit for receiving a first gamma photon and the position of a second bar-shaped detection unit for receiving a second gamma photon according to an encoding signal channel with the output of 1 in the first group of logic values and an encoding signal channel with the output of 1 in the second group of logic values so as to obtain the incident position coordinates of the first gamma photon and the incident position coordinates of the second gamma photon;
obtaining corresponding annihilation angle according to the incident position coordinate and the position coordinate of the sample
。
5. The positron annihilation angle correlation measurement apparatus of claim 4, wherein the processor is further configured to pair annihilation angles within a preset time period
Counting the value to obtain
Distribution of values to obtain a one-dimensional positron annihilation angle correlation spectrum。
6. The positron annihilation angle correlation measurement apparatus according to any one of claims 1-5, wherein the angular resolution of the measurement apparatus is
Wherein, in the step (A),
for the width of each of the detection units,
is the distance between the sample and the first and second fixed detectors.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010387948.2A CN111487667B (en) | 2020-05-09 | 2020-05-09 | Positron annihilation angle correlation measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010387948.2A CN111487667B (en) | 2020-05-09 | 2020-05-09 | Positron annihilation angle correlation measuring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111487667A CN111487667A (en) | 2020-08-04 |
| CN111487667B true CN111487667B (en) | 2022-08-19 |
Family
ID=71813295
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010387948.2A Active CN111487667B (en) | 2020-05-09 | 2020-05-09 | Positron annihilation angle correlation measuring device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111487667B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113655513A (en) * | 2021-08-16 | 2021-11-16 | 中国科学技术大学 | Digitized anti-coincidence multi-path interaction-starting positron annihilation life spectrometer |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5530245A (en) * | 1994-05-09 | 1996-06-25 | Huang; Wei-Feng | Surface characterization of catalytic materials by positron annihilation radiation lineshapes measurements |
| US5793045A (en) * | 1997-02-21 | 1998-08-11 | Picker International, Inc. | Nuclear imaging using variable weighting |
| KR101241821B1 (en) * | 2011-08-04 | 2013-03-18 | 고려대학교 산학협력단 | Apparatus and method for acquiring positron emission tomography ucsing compton events, and a medium having computer readable program for executing the method |
| CN102967874B (en) * | 2012-12-17 | 2015-01-21 | 中国科学院高能物理研究所 | Positive electron annihilation angle correlation spectrometer |
| US20150123003A1 (en) * | 2013-11-06 | 2015-05-07 | University Of Kentucky Research Foundation | High resolution absorption imaging using annihilation radiation from an external positron source |
-
2020
- 2020-05-09 CN CN202010387948.2A patent/CN111487667B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN111487667A (en) | 2020-08-04 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102507623B (en) | Non-scanning type wavelength dispersion X-ray fluorescence spectrometer | |
| CN102967874B (en) | Positive electron annihilation angle correlation spectrometer | |
| KR20190022862A (en) | Pixelated gamma detector | |
| US20220326399A1 (en) | System and method for neutron and gamma radiation detection using non-homogeneous material scintillator | |
| CN111487667B (en) | Positron annihilation angle correlation measuring device | |
| CN112764086A (en) | Miniaturized compound gamma spectrometer | |
| CN111487664B (en) | Positron annihilation angle correlation measurement device and method based on positioning algorithm | |
| CN112014873A (en) | Method for rapidly determining action depth positioning resolution of double-end reading detector | |
| CN111487666B (en) | Positron annihilation angle correlation measurement method | |
| JP4695640B2 (en) | Method and apparatus for denying random coincidence in positron emission cross section | |
| EP2116869A1 (en) | Gamma ray detector and pet device employing the same | |
| CN111596336B (en) | Multi-gamma photon coincidence imaging system and method based on slit-hole flat plate collimator | |
| US11262462B2 (en) | Detection method and detector apparatus for correcting count rate for dead time | |
| CN111487665B (en) | Two-dimensional positron annihilation angle correlation measurement device and method | |
| Thiel et al. | High-energy photon detection with LYSO crystals | |
| Wehe David | Current trends in ionizing radiation detection | |
| Chong et al. | High Data-Rate Neutron-Sensitive Pixelated Detector Using Silicon Photomultiplier | |
| Tong et al. | Positron emission tomography detector performance with different crystal pitches | |
| CN113640852A (en) | Positron annihilation life spectrometer for measuring film sample | |
| CN220231986U (en) | Acquisition device for detecting radon content | |
| López-Robles et al. | Improving MWPC delay line readout by waveform analysis | |
| Aprile et al. | Initial results on calorimetry and imaging of MeV gamma rays with a 10-liter liquid xenon time projection chamber (LXe-TPC) | |
| Goertzen et al. | PET instrumentation | |
| Akhdar | Development of a high resolution 3D gamma camera | |
| Kalousis | SoLid: Search for oscillations with a 6Li detector |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |