Research On Low-yield γ Pulse Source Detection Technology

Pulsedγrays,often accompanied by the production of pulsed neutrons.Low yield（10²～10⁵ particles/pulse）pulseγsource,as a special pulse radiator,its measurement can reflect the information of the pulse neutron source.Therefore,low-yield pulseγdetection technology has important application value in the design and diagnosis of inertial confinement fusion（ICF）,high density plasma focusing device（DPF）,spallation neutron source,pulse reactor and pulse neutron logging device.There are no reports of measurement technology for low-yield pulseγsources in the published literature at home and abroad,and the detector working mode（counting type,current type）used in conventionalγsource measurement is no longer applicable under the low-yield scenario.A new detector working mode needs to be found.In order to measure the yield and emission time of a single launch of a low-yield pulseγsource,new inorganic lanthanum bromide（La Br₃:Ce）scintillator detectors with high detection efficiency and fast time response was selected as the detection units.A large three-dimensional angle detection array device constructed by 48 detection units was designed and built,and an array detection technology based on Poisson distribution statistical theory was developed,which verified that the technology could give yield and time information of low-yield pulseγsource with high credibility.The main research work of the thesis is as follows:The performance research of 9815B photomultiplier tubes supporting lanthanum bromide crystal was carried out,and key performance parameters such as gain and maximum pulse linear current of 60 photomultiplier tubes were obtained.The self-made voltage divider circuit for photomultiplier tubes was tested and adjusted to obtain the optimal working voltage division ratio of each photomultiplier tube,so that the magnification was basically consistent;The assembled detector was calibrated using the ¹³⁷Cs standard source,and the results showed that the signal output current of all detectors to the 662 ke V full energy peak was within 14 m A,which met the measurement requirements of the detector array.Based on the cascade emission characteristics of the ⁶⁰Co standard source,the transition time of all detectors was measured by the compliance method,and the Gaussian fitting of the collected conforming waveform data was processed using the Matlab program,and the detectors with the dispersion of the transition time within2.00 ns were screened out to meet the time measurement requirements of the detector array.Based on the experimental spatial geometric distribution,the physical model of the pulseγsource measurement process was determined by parameters such as the full-spectrum detection efficiency and measurement threshold of the lanthanum bromide detector.Through computational analysis,the experimental conditions of pulsed X-ray machine equivalent low-yield pulseγsource were determined.Pulse yield and emission time of the developed lanthanum bromide detector array were measured,which verified the feasibility of the lanthanum bromide array detection technology proposed in this work.The research results on the measurement technology of the low-yield pulseγsource not only provide a new detection technology for pulsed gamma radiation detection,but also provide data support for obtaining relevant information such as pulsed neutron source yield,which has certain promotion and application value.