CN111650228B - Positron annihilation spectrum testing method for powder or liquid sample - Google Patents
Positron annihilation spectrum testing method for powder or liquid sample Download PDFInfo
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- CN111650228B CN111650228B CN202010626423.XA CN202010626423A CN111650228B CN 111650228 B CN111650228 B CN 111650228B CN 202010626423 A CN202010626423 A CN 202010626423A CN 111650228 B CN111650228 B CN 111650228B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/07—Investigating materials by wave or particle radiation secondary emission
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2223/10—Different kinds of radiation or particles
- G01N2223/108—Different kinds of radiation or particles positrons; electron-positron annihilation
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- G01N2223/318—Accessories, mechanical or electrical features protective films
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- G—PHYSICS
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- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/60—Specific applications or type of materials
- G01N2223/62—Specific applications or type of materials powders
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
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- G01N2223/637—Specific applications or type of materials liquid
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Abstract
The invention provides a method for testing positron annihilation spectra of powder or liquid samples, which uses a Kapton film to wrap positron emission substances to form a positron emission source; the positron radioactive source is wrapped by a film with known positron annihilation characteristics and is placed in a self-sealing bag, and a sufficient amount of sample to be measured is filled in the self-sealing bag; the positive electron source emits positrons at a certain speed, and the positrons are injected into the detected material and annihilated in the material; the positron annihilation lifetime spectrum is generated by detecting a generated optical signal and an annihilation optical signal of a positron by using a scintillator probe, sequentially passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer, recording information by a computer, and finally generating the positron annihilation lifetime spectrum containing a large amount of annihilation data. The invention can test the positron annihilation life spectra of liquid and powder samples, does not need tabletting in the test process, does not damage the structures of the liquid and powder samples, and does not have the risks of pollution and damage of positron radioactive sources in the test.
Description
Technical Field
The invention belongs to the technical field of material microstructure detection, and particularly relates to a positron annihilation spectrum testing method for a powder or liquid sample.
Background
Advances in materials science can dramatically advance the development of a wide range of industrial technologies. The discovery of a new high-performance material has a great promotion effect on the frontier science. However, the development of new materials is also difficult. From the microscopic point of view, it is more and more important to develop new materials by studying the mechanism of the microstructure of the material affecting its macroscopic properties. However, it is difficult to obtain information on the internal structure of the organic material, such as phase morphology, free volume, nanopore morphology, and chemical environment change, by conventional experimental means.
Positron annihilation is a core technique that uses the annihilation characteristics of positrons in a material under test to characterize the microstructure in the material under test. Positrons are antiparticles of electrons, with a positive charge. A large number of positrons enter the material and annihilate at various locations within the material and carry annihilation signatures (lifetime length, intensity, etc.). At this time, the annihilation characteristics of the positron are closely related to defects at the annihilation position, the free volume, the chemical environment, and the like, and therefore the microstructure inside the material can be estimated using these annihilation characteristics.
In practice, the positron-emitting material (commonly used as such) is applied using a Kapton film22Na，18F，11C, etc.) to form a sealed positron emission sample contactable with the solid sampleA source. Two samples to be tested are placed on two sides of the positive electron source to form a sandwich structure (as shown in figure 1). And finally, putting the sample and the radioactive source into a self-sealing bag together for testing. If the tested sample is a powder sample, the powder sample needs to be pressed into a sheet shape before testing, and the sheet pressing process is very likely to damage the structure of the powder sample to some extent, is not beneficial to recycling of the sample and is not beneficial to analysis of the microstructure of the sample. Moreover, the sample after tabletting has an unstable structure and is likely to be damaged in the testing process, and the damaged powder is very likely to pollute the positron emission source. Furthermore, some powder samples were not pressed into a tablet shape and could not be tested. Liquid samples contaminate the radioactive source and are therefore often not tested. Therefore, this defect greatly limits the application of positron annihilation techniques to powder and liquid samples. After the positron emission source and the sample are arranged, the positive electron source emits positrons at a certain speed, and the positrons are injected into the detected material and annihilated in the material. The positron annihilation lifetime spectrum is generated by detecting a generated optical signal and an annihilation optical signal of a positron by using a scintillator probe, sequentially passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer, recording information by a computer, and finally generating the positron annihilation lifetime spectrum containing a large amount of annihilation data. Typically each positron annihilation lifetime spectrum consists of 1000000-2000000 counts. Finally, required data is extracted from the positron annihilation lifetime spectrum as required. Positron annihilation techniques have therefore been widely used for decades to detect the microscopic structures of various materials.
Positron emitting substances (commonly used as such) are delivered using Kapton film22Na，18F，11C, etc.) to form a sealed positron-emitting source that can be contacted with a solid sample.
When testing the solid sample, two tested samples are placed on two sides of the positive electron source to form a sandwich structure. The sample is placed in a self-sealing bag together with a radioactive source and is ready for testing. After a positron radioactive source and a sample are arranged, a scintillator probe is used for detecting a generated light signal and an annihilation light signal of a positron, then information is recorded by a computer after passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer in sequence, and finally a positron annihilation life spectrum is generated. Typically each positron annihilation lifetime spectrum consists of 1000000-2000000 counts. Finally, the required data is extracted from the positron annihilation lifetime spectrum as required.
When testing the powder sample, a tablet press is used to press two tablet samples with the same pressure and time before testing. And then a positron emission source and a sample are arranged according to the method, and the positron annihilation lifetime spectrum is tested.
Liquid samples contaminate the radioactive source and are therefore often not tested.
In summary, the prior art has the following problems:
1. the powder sample needs to be pressed into a sheet shape when being tested, and the sheet pressing process is very likely to damage the structure of the powder sample to a certain extent, so that the recycling of the sample and the analysis of the microstructure of the sample are not facilitated.
2. The powder sample after tabletting has an unstable structure and is likely to be damaged in the testing process, and the damaged powder is very easy to pollute the positron emission source.
3. Some powder samples were not pressed into tablets and were not tested.
4. Liquid samples contaminate the radiation source and therefore their positron annihilation lifetime spectra cannot usually be measured.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for testing positron annihilation spectra of powder and liquid samples, which is used for testing the positron annihilation lifetime spectra of the powder and liquid samples on the basis of not destroying the sample structure and polluting radioactive sources.
The specific technical scheme is as follows:
a positron annihilation spectroscopy test method for a powder or liquid sample, comprising the steps of:
(1) wrapping a positron emitting substance with a Kapton film to form a sealed positron emitting source which can be contacted with a solid sample;
(2) the positron emission source is wrapped by a film with known positron annihilation characteristics, and the positron emission source is sealed; the positron radiation source sealed by the envelope is placed in a self-sealing bag with a proper size, and sufficient powder or liquid samples to be tested are filled in the self-sealing bag;
(3) after a positron radioactive source and a sample are arranged, a positive electron source emits positrons at a certain speed, and the positrons are injected into a detected material and annihilated in the material;
(4) the positron annihilation lifetime spectrum is generated by detecting a generated optical signal and an annihilation optical signal of a positron by using a scintillator probe, sequentially passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer, recording information by a computer, and finally generating the positron annihilation lifetime spectrum containing a large amount of annihilation data.
The film with known positron annihilation characteristics is an ultrathin Mylar film, and the thickness of the film is less than or equal to 10 mu m. The ultrathin Mylar film has the substitutability, such as some high molecular films, which have the characteristics of stability, strong rigidity, ultrathin property, known positron annihilation and convenient heat sealing.
Typically each positron annihilation lifetime spectrum consists of 1000000-2000000 counts. After a sample is measured, the positron emission source sealed by the Mylar film is taken out, the Mylar film is cut open, and the positron emission source is taken out. The next test re-uses the ultra thin Mylar film to seal the positron emitting source. It should be mentioned in particular that the use of ultra-thin Mylar film has the advantage of being structurally stable and difficult to corrode from powder and liquid samples. And the positron has strong penetrability, only a very small amount of positrons can be annihilated in the middle of the ultrathin Mylar film, and the influence on the test result is very small. Also, the positron annihilation characteristics in the Mylar film are known and stable and can be removed by "source correction" during subsequent unscrambling. Thus, the ultra-thin Mylar film can protect the positron emitting source from contamination by the sample and does not itself affect the test results of positron annihilation techniques.
The positron annihilation spectrum testing method for the powder and liquid samples provided by the invention has the following technical effects:
1. the positron annihilation lifetime spectrum of liquid and powder samples can be tested.
2. The test process does not need tabletting and does not damage the structure of liquid and powder samples.
3. Positron emitting sources are expensive and leaks are difficult to handle. The method has no risk of pollution and damage to the positron radioactive source during testing.
Drawings
FIG. 1 is a schematic illustration of a prior art positron emitting source and sample placement method;
FIG. 2 is a schematic illustration of the testing method of the present invention;
FIG. 3 is a positron annihilation lifetime spectrum of potato starch (8 wt% moisture content) as measured in example 1;
FIG. 4 is a positron annihilation lifetime spectrum of potato starch (15 wt% moisture content) as measured in example 2;
FIG. 5 is a positron annihilation lifetime spectrum of potato starch (30 wt% moisture content) as measured in example 3.
Detailed Description
The embodiments of the present invention will be described with reference to the accompanying examples.
As shown in FIG. 2, positron-emitting substances (commonly used as such) are applied using a Kapton film22Na，18F，11C, etc.) to form a sealed positron-emitting source that can be contacted with a solid sample. The positron radioactive source is wrapped by an ultrathin Mylar film (the thickness is less than or equal to 10 mu m), and the positron radioactive source is sealed by means of heat sealing and the like. The positron emission source sealed by the Mylar film is placed in a self-sealing bag with a proper size, and a sufficient amount of powder or liquid to be tested is filled in the self-sealing bag, as shown in fig. 2. After the positron emission source and the sample are arranged, the positive electron source emits positrons at a certain speed, and the positrons are injected into the detected material and annihilated in the material. The positron annihilation lifetime spectrum is generated by detecting a generated optical signal and an annihilation optical signal of a positron by using a scintillator probe, sequentially passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer, recording information by a computer, and finally generating the positron annihilation lifetime spectrum containing a large amount of annihilation data.
Example 1
Use Kapton film will emit positron emission material (commonly used as22Na，18F，11C, etc.) to form a sealed positron-emitting source that can be contacted with a solid sample. The positron radioactive source is wrapped by an ultrathin Mylar film (the thickness is less than or equal to 10 mu m), and the positron radioactive source is sealed by means of heat sealing and the like. The positron emission source sealed by the Mylar film is placed in a self-sealing bag with a proper size, and about 20g of potato starch with the water content of 8 wt% is filled in the self-sealing bag, so that the positron emission source is completely wrapped by the starch. After the positive electron source and the potato starch are arranged, the positive electron source emits positive electrons at a certain speed, and the positive electrons are injected into the potato starch to be annihilated. A scintillator probe is used for detecting a generated light signal and an annihilation light signal of a positron, then information is recorded by a computer after passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer in sequence, and finally a positron annihilation lifetime spectrum is generated, as shown in fig. 3.
Example 2
Positron emitting substances (commonly used as such) are delivered using Kapton film22Na，18F，11C, etc.) to form a sealed positron-emitting source that can be contacted with a solid sample. The positron radioactive source is wrapped by an ultrathin Mylar film (the thickness is less than or equal to 10 mu m), and the positron radioactive source is sealed by means of heat sealing and the like. The positron emission source sealed by the Mylar film is placed in a self-sealing bag with a proper size, and about 20g of potato starch with the water content of 15 wt% is filled in the self-sealing bag, so that the positron emission source is completely wrapped by the starch. After the positive electron source and the potato starch are arranged, the positive electron source emits positive electrons at a certain speed, and the positive electrons are injected into the potato starch to be annihilated. A scintillator probe is used for detecting a generated light signal and an annihilation light signal of a positron, then information is recorded by a computer after passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer in sequence, and finally a positron annihilation lifetime spectrum is generated, as shown in fig. 4.
Example 3
Positron emitting substances (commonly used as such) are delivered using Kapton film22Na，18F，11C, etc.) to form a sealed positron-emitting source that can be contacted with a solid sample. The positron radioactive source is wrapped by an ultrathin Mylar film (the thickness is less than or equal to 10 mu m), and the positron radioactive source is sealed by means of heat sealing and the like. The positron emission source sealed by the Mylar film is placed in a self-sealing bag with proper size, and about 20g of potato starch with the water content of 30 wt% is filled in the self-sealing bag, so that the positron emission source is completely wrapped by the starch. After a positron radiation source and potato starch are arranged, a positive electron source emits positrons at a certain speed, and the positrons are injected into the potato starch to be annihilated. A scintillator probe is used for detecting a generated light signal and an annihilation light signal of a positron, then information is recorded by a computer after passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer in sequence, and finally a positron annihilation lifetime spectrum is generated, as shown in fig. 5.
Claims (1)
1. A positron annihilation spectroscopy test method for a powder or liquid sample, comprising the steps of:
(1) wrapping a positron emitting substance with a Kapton film to form a sealed positron emitting source which can be contacted with a solid sample;
(2) the positron emission source is wrapped by a film with known positron annihilation characteristics, and the positron emission source is sealed; the positron radiation source sealed by the envelope is placed in a self-sealing bag with a proper size, and sufficient powder or liquid samples to be tested are filled in the self-sealing bag; the film with known positron annihilation characteristics is an ultrathin Mylar film, and the thickness of the film is less than or equal to 10 mu m;
(3) after a positron emission source and a sample are arranged, a positive electron source emits positrons at a certain speed, and the positrons are injected into a detected material and annihilated in the material;
(4) the positron annihilation lifetime spectrum is generated by detecting a generated light signal and an annihilation light signal of a positron by using a scintillator probe, sequentially passing through a constant ratio timing discriminator, a time-amplitude converter and a multichannel analyzer, recording information by a computer, and finally generating the positron annihilation lifetime spectrum containing a large amount of annihilation data.
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| US7041508B2 (en) * | 2002-02-06 | 2006-05-09 | Alerttechsystems, Llc | Positron annihilation monitor and method for detecting hazardous materials |
| JP4299064B2 (en) * | 2003-06-19 | 2009-07-22 | 啓明 三頭 | Manufacturing method of sealed 210Pb-210Poα radiation source (α particle emitter) |
| JP5843315B2 (en) * | 2010-11-24 | 2016-01-13 | 国立研究開発法人産業技術総合研究所 | Positron annihilation characteristic measuring apparatus and positron annihilation characteristic measuring method |
| CN202870004U (en) * | 2012-06-07 | 2013-04-10 | 中国科学院高能物理研究所 | Positron annihilation multi-parameter accordance measurement system |
| CN103336020B (en) * | 2013-07-17 | 2015-07-15 | 苏州热工研究院有限公司 | Positron lifetime spectrum measurement system and adopted measurement method thereof |
| CN106680300B (en) * | 2017-01-17 | 2019-04-09 | 武汉大学 | Various dimensions positron annihilation lifetime spectrum and dopplerbroadening spectral measurement system |
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