10 results about "Positron annihilation" patented technology

The invention discloses a helium bubble size and density analysis method based on positron annihilation multiple parameters. The helium bubble size and density analysis method comprises the following steps: 1) calculating a low momentum annihilation ratio S and a high momentum annihilation ratio W according to Doppler broadening DBS of a sample to be detected; 2) obtaining the life value of each helium bubble in the sample to be detected according to the life spectrum PALS of the sample to be detected; (3) determining the helium bubbles in the sample to be detected and the types of the helium bubbles according to the service life values of the S, the W and the helium bubbles; 4) comparing the service life value of each helium bubble in the to-be-tested sample with the corresponding service life value calculated by the first principle to obtain the type of the helium bubble in the to-be-tested sample; the radiuses of the helium bubbles of different types are converted into sphere radiuses, and the helium bubble radiuses of the helium bubbles in the sample to be detected are obtained; 5, the matrix life, the helium bubble defect life and the average life of the sample to be measured are obtained according to the life spectrum PALS, and the helium bubble density is obtained through calculation according to the two-state capture model.The helium bubble evaluation robustness is improved.

The application discloses a kind of thermoset elastomer thermal aging state evaluation method, comprising the following steps: S1, elastomer is treated with heat aging;S2, the maximum elongation of aging sample and positron annihilation lifetime spectrum are tested, and the free volume of aging sample is obtained by analyzing positron annihilation lifetime spectrum;S3, least square method is used to linearly fit the maximum elongation of aging sample and free volume, and the fitting equation of maximum elongation and free volume of elastomer in the process of thermal aging treatment is established;S4, in the actual thermal aging test of the same kind of elastomer, the fitting equation is used, and the maximum elongation of elastomer is calculated by determining the free volume of elastomer, and the thermal aging state of elastomer is evaluated.The application establishes the correlation between the maximum elongation of elastomer and free volume, realizes the thermal aging state of elastomer by free volume, realizes in-situ detection of thermal aging performance, and has high accuracy.

The application discloses a positron annihilation lifetime measurement device and method for thin film sample characterization, which is composed of a positron emitter, a positron detector and a gamma detector; a sample is placed between the positron emitter and the positron detector. The positron emitter contains a radioactive source and is responsible for detecting the positrons entering the sample, and the positron detector is responsible for detecting the positrons penetrating the sample. The gamma detector is responsible for detecting the 0.511 MeV gamma photons generated after the positrons are annihilated. The application can break through the limitation of measuring the sample thickness, is suitable for all types of positron radioactive sources, and sufficiently widens the experimental conditions; meanwhile, the non-contact measurement function can expand the application of the positron annihilation lifetime measurement method in the measurement of special samples and special environments.

The invention relates to the technical field of positron annihilation lifetime measurement, and provides a positron annihilation lifetime spectrum measurement device, which comprises an alpha particle generation device, an alpha particle detection device, a gamma ray detection device and a lifetime measurement device, and is characterized in that the alpha particle generation device generates alpha particles and first gamma rays through nuclear reaction; the first gamma ray enters a to-be-detected sample, and positron annihilation occurs in the to-be-detected sample to emit a second gamma ray; the alpha particle detection device is used for detecting alpha particles and generating an initial signal; the gamma ray detection device is used for detecting a second gamma ray and generating a termination signal; the lifetime measuring device is used for acquiring a time interval between the start signal and the termination signal to generate a positron annihilation lifetime spectrum. As alpha particles are easy to shield and the detection efficiency is higher than that of gamma rays, the alpha particles are used as initial signals, so that the screening efficiency of effective events and the overall counting rate of the system can be greatly improved, and the positron annihilation lifetime spectrum has good signal-to-noise ratio and measurement accuracy.

The application provides a source device-based positron annihilation lifetime measurement system and method, which comprises a source chamber, a start gamma detector, a stop gamma detector and a positron detector. 22 The Na radioactive source is fixed on the surface of the source chamber, the source chamber and the positron detector are placed on the two sides of the thin film sample and are symmetrically opposite, and the positions are relatively fixed; the start gamma detector and the stop gamma detector are placed on the two sides of the positron detector and are responsible for detecting the 1.28 MeV gamma photons generated by the cascade when the positron is emitted by the radioactive source and the 0.511 MeV gamma photons generated after the positron annihilation. The application can effectively remove the noise positrons by improving the positron range on the non-sample side, reducing the detection efficiency of the far-end annihilation gamma photons, and reducing the size of the electronics; the positron annihilation position on the sample side can be accurately identified, the non-sample positron annihilation components can be excluded, the sample thickness limitation can be broken, and the thin film sample positron annihilation lifetime measurement can be realized.

This invention relates to a high-intensity pulsed X-ray beam monitoring device and method, applicable to flash therapy. The high-intensity pulsed X-ray beam monitoring device of this invention uses a conversion target to convert a high-intensity pulsed X-ray beam into low-intensity electron-positron annihilation gamma rays. A ring detector array is set around the conversion target to capture the electron-positron annihilation gamma rays and calculate and determine their emission positions. The intensity of the X-ray beam under test is estimated by the intensity of the electron-positron annihilation gamma rays and the conversion efficiency of the conversion target; valid coincidence events are screened, and the coordinates of the annihilation positions are reconstructed using filtered back projection based on the signals of multiple coincidence events, obtaining the shape distribution of the X-ray beam and the intensity distribution of the beam interface.

The invention relates to a novel positron annihilation lifetime-momentum correlation spectrometer and a measurement method thereof.The novel positron annihilation lifetime-momentum correlation spectrometer comprises a detector module, a data acquisition module and a data processing module, the detector module comprises two scintillator detectors and two high-purity germanium detectors, in the two scintillator detectors, one scintillator detector serves as an initial scintillator detector for detection, and the other scintillator detector serves as a second high-purity germanium detector for detection; the other scintillator detector is used as a termination scintillator detector to measure a positron annihilation lifetime spectrum; the high-purity germanium detector is used for measuring Doppler broadening during positron annihilation; the data acquisition module comprises acquisition equipment with four analog input channels, and is used for acquiring pulse signals output by the detector module; the data processing module processes the collected data and draws a positron annihilation life-momentum correlation spectrum. According to the invention, the counting rate of the positron annihilation lifetime-momentum correlation spectrometer is improved, rapid acquisition and rapid processing of pulse signals are realized, the resolution of time measurement and the precision of a time spectrum are improved, and the application of the technology in the field of material science is expanded.

A PET imaging system includes BGO crystals that generate Cherenkov photons in response to excitation by photons from positron annihilation events and photosensors configured to detect the Cherenkov photons and generate signals indicative thereof, an LOR determiner configured to identify, based on the signals, coincident photon pairs along each LOR, a TOF determiner configured to determine a timing resolution for each of the coincident photon pair along each LOR, an accuracy determiner configured to bin the LORs, based on the timing resolutions, into at least higher accuracy TOF LORs and lower accuracy TOF LORs, a reconstructor configured to reconstruct the higher accuracy TOF LORs using models and generate volumetric image data, and a model adjuster configured to adjust at least one model of the models based on the volumetric image data. The reconstructor is configured to reconstruct at least a subset of the LORs using the updated models.

The present application relates to the technical field of nuclear power plant radiation monitoring, and particularly relates to a primary loop pressure boundary leakage radiation monitoring device and a monitoring method thereof. 18 F has a long half-life, positron annihilation and other characteristics, and the gamma-gamma digital coincidence measurement technology is applied to the primary loop pressure boundary leakage monitoring, quantitative monitoring of the primary loop pressure boundary leakage rate is realized, the anti-interference capability of the system is improved, the detection lower limit of the system is reduced, and the system is miniaturized to a certain extent.

The present application relates to a performance prediction method for modified layered oxide electrode materials, comprising the following steps: pressing unmodified layered oxide electrode materials and modified layered oxide electrode materials into sheets under the same pressure to obtain unmodified layered oxide electrode material sheets and modified layered oxide electrode material sheets; respectively performing positron annihilation lifetime spectrum testing and spectrum analysis on the unmodified layered oxide electrode material sheets and the modified layered oxide electrode material sheets; and calculating the ion capacity and / or ion transmission rate of the modified layered oxide electrode materials. The performance prediction method is simple and efficient, and the predicted results are accurate, which helps to shorten the test period of electrode material related performance and reduce the measurement cost.