23 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 invention discloses a high-efficiency multichannel positron annihilation lifetime measurement method and device. The method comprises the following steps: 1) detecting instant gamma photons generated by positron of a target radioactive source and positron annihilation gamma photons by using a plurality of detectors, converting the instant gamma photons and the positron annihilation gamma photons into analog signals, and sending the analog signals to a sampling circuit; 2) a sampling circuit is responsible for sampling and digitally processing analog signals generated by each detector and then uploading the analog signals to an upper computer; and 3) the upper computer analyzes and processes the uploaded data to obtain the positron annihilation lifetime of the target radioactive source. The sampling circuit comprises a trigger module, a sampling module, a digital module and a control module. The control module configures each module according to a program issued by upper computer program control software. When the detector input signal meets the setting of the trigger module, the sampling module starts or stops sampling the detector signal of each channel; the digital module carries out digital processing on the signals, converts the signals into data and uploads the data to an upper computer.

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 invention relates to a performance prediction method for a modified layered oxide electrode material, and the method comprises the following steps: pressing an unmodified layered oxide electrode material and a modified layered oxide electrode material into sheets under the same pressure, obtaining an unmodified layered oxide electrode material sheet and a modified layered oxide electrode material sheet; respectively carrying out positron annihilation life spectrum testing and spectrum unfolding on the unmodified layered oxide electrode material sheet and the modified layered oxide electrode material sheet; and calculating the ion capacity and / or ion transmission rate of the modified layered oxide electrode material. The performance prediction method is simple and efficient, the accuracy of the predicted result is high, the test period of the related performance of the electrode material is shortened, and the measurement cost is reduced.

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.

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.

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.

The application discloses a kind of system and method for promoting TOF-PET system counting rate.The system includes a data processing module and multiple acquisition units, each acquisition unit includes a detector module and an electronics module;Detector module is used to detect the gamma photon pair generated by positron annihilation in the detected object, and the nuclear signal generated according to the detected gamma photon pair is converted into electrical signal input electronics module;Electronics module selects the input electrical signal to obtain real coincidence event for acquisition;Data processing module is used to receive the same coincidence time window as a pair of real coincidence events with two real coincidence events, calculate the time difference of two real coincidence events in each pair of real coincidence events to its corresponding detector module, and determine the position of the detected object according to the statistical result of the time difference of each pair of real coincidence events.Theoretical effective counting rate can be improved several times or even an order of magnitude, which greatly improves the sensitivity of the system.

The present invention provides a composite semipermeable membrane and a composite semipermeable membrane element that exhibit excellent monovalent ion / multivalent ion permselectivity under acidic conditions. The present invention relates to a composite semipermeable membrane having a porous support layer and a separation functional layer on one face side of the porous support layer, the separation functional layer containing a semi-aromatic crosslinked polyamide, the face of the separation functional layer side of the composite semipermeable membrane being set as a first face, the face on the side opposite the first face being set as a second face, a positron beam being irradiated from the first face side of the composite semipermeable membrane, the average pore diameter R1 of the separation functional layer under conditions of a positron beam intensity of 0.1 keV and the average pore diameter R2 of the separation functional layer under conditions of a positron beam intensity of 0.5 keV derived from positron annihilation lifetime measurement being 0.30 nm or more and 2.00 nm or less, and satisfying 0.90 ≤ R1 / R2 ≤ 1.10.

The present invention discloses a method for detecting the flow field of an aero-engine inlet duct based on a positron annihilation technology. The method comprises the following steps: installing a wind tunnel tube in an annular gamma photon detector, installing a fairing at one end of the wind tunnel tube away from the annular gamma photon detector, and connecting one end of the wind tunnel to a wind tunnel blower; arranging an inlet duct bracket in the wind tunnel tube; fixing the inlet duct to be detected on the inlet duct bracket; planting cotton threads on a silica gel plate in a linear array manner; preparing a radionuclide-labeled aqueous solution to be adsorbed on the cotton threads; fixing the silica gel plate in an inner cavity of the inlet duct to be detected; starting the wind tunnel blower, collecting gamma photon pairs generated by positron annihilation on the cotton threads in the inlet duct through the annular gamma photon detector, and storing the collected gamma photon pairs as three-dimensional sinusoidal graphs; performing interpolation processing on the three-dimensional sinusoidal graphs to expand data; and performing three-dimensional image iterative reconstruction based on the processed three-dimensional sinusoidal graphs to obtain a clear flow field state in the inner cavity of the aero-engine inlet duct.

The invention discloses a positron annihilation parameter spectrogram measuring system and method. The system comprises a positron source, n coding matrixes, a single-pixel detector and an atlas reconstruction module, the positron source is used for emitting an initial positron beam X to the coding matrix; the coding matrix is used for modulating the initial positron beam X to form a modulated positron source Y which is incident on a sample target; the single-pixel detector is used for detecting energy, time or direction of gamma photons generated after each modulated positron source enters the sample target to obtain a corresponding positron annihilation spectrum P and sending the positron annihilation spectrum P to the atlas reconstruction module; and the atlas reconstruction module is used for calculating positron annihilation spectrums Q of sample target areas corresponding to matrix elements allowing positron particles to pass through in each coding matrix according to the n positron annihilation spectrums P, and then generating a positron annihilation parameter spectrogram of the sample target according to a positron annihilation spectrum Q set.

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 application relates to a positron annihilation lifetime measurement system, which comprises a box assembly, a radioactive source, an operation platform and a detector arranged in the operation box. The radioactive source is arranged on the operation platform and is used for emitting positrons to a sample to be measured. The detector is arranged for measuring the positron annihilation lifetime. A shielding layer is arranged on the outer surface of the box assembly and shields the radiation generated by the radioactive source. A first taking and placing opening is arranged on the shielding layer and is communicated with the inner cavity of the operation box. The shielding layer is provided with a first shielding door which is hinged to the shielding layer. The first shielding door can rotate around the hinge point of the first shielding door and the shielding layer to close and open the first taking and placing opening. In the embodiment, the shielding layer is arranged on the outer surface of the box assembly to isolate the box assembly from the external environment, so that the body of an external worker can be prevented from being radiated by a radioactive sample, and safe measurement of the radioactive sample is realized.

The invention discloses a positron annihilation lifetime spectrometer system with three-dimensional position resolution capability, which belongs to the technical field of nuclear detection and comprises a positron annihilation lifetime measuring device and a high-precision X-Y plane moving device. The positron annihilation life measuring device is used for acquiring annihilation characteristics of positron in different depth intervals within a millimeter depth range from the surface of a material, and comprises a life starting module and a life ending module which are respectively connected with an information acquisition module, and the information acquisition module is connected to a control and processing module; the high-precision X-Y plane moving device is used for moving the detector part of the positron annihilation life measuring device so as to realize scanning test of an X-Y plane, and comprises three servo motors and three sliding rails respectively controlled by the servo motors. According to the invention, three-dimensional space characterization can be carried out on microstructure characteristics of different depth intervals in a millimeter-level depth range from different areas of the surface of the material to the surface.

To provide ferritic stainless steel foil that offers excellent corrosion resistance.SOLUTION: The ferritic stainless steel foil disclosed in this invention comprises a foil main body made of ferritic stainless steel. The S parameter obtained from the positron annihilation coincidence Doppler broadening method measurement of the foil main body is 0.592 or more, and the W parameter is 2.80×10-3 or less.SELECTED DRAWING: None

This invention discloses a β + This invention relates to a γ-γ coincidence positron annihilation lifetime-momentum correlation spectrometer, belonging to the field of nuclear detection technology. The spectrometer includes a positron annihilation lifetime detection module, a positron annihilation γ-photon energy detection module, a signal acquisition module, and a control and analysis module. The positron annihilation lifetime detection module is used to obtain the lifetime component of the AMOC spectrum; the positron annihilation γ-photon energy detection module is used to obtain the momentum component of the AMOC spectrum by detecting γ-photons generated by positron annihilation; the signal acquisition module is used to acquire the signals generated by the positron annihilation lifetime detection module and the positron annihilation γ-photon energy detection module; and the control and analysis module is used to control the signal acquisition module and obtain the AMOC spectrum based on the signals acquired by the signal acquisition module. This invention can effectively improve the coincidence count rate, has good coincidence time resolution and extremely low source composition, and helps to reduce the construction cost of the spectrometer.

The application discloses a kind of based on β + The coincidence signal generating module is used to detect the positron generated by the decay of positron source, and generate coincidence signals for event selection. The annihilation gamma photon detection module is used to detect the gamma photon generated by positron annihilation, and generate pulse signals containing energy information. The signal acquisition module is used to acquire coincidence signals and pulse signals. The control and analysis module is used to control the signal acquisition module and obtain the positron annihilation coincidence Doppler broadening spectrum from the acquired coincidence signals and pulse signals. The positron annihilation coincidence Doppler broadening spectrometer of the application can achieve a very low source component ratio, thereby improving the accuracy of test results.

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 invention discloses a trajectory reconstruction algorithm for PEPT tracer particles. The algorithm performs frame division and positioning processing on line of response (LoRs) data captured by a PEPT detector, and performs overlapping segmentation of the data through a sliding window method to improve the utilization rate of the LoRs data, thereby increasing the positioning frequency of the PEPT tracer particles. At the same time, the center points of the shortest segments of two non-planar straight lines are introduced into the positioning process as the approximate positions of the lines of response (LoRs) emitted by two positron annihilations, so that the positioning process is closer to the actual physical process and has a higher positioning frequency of the PEPT tracer particles.

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.