The Research On Device For Measuring Decay Time Of Common Inorganic Scintillator

In general nuclear physics experiments,the indicators that describe the physical properties of the scintillator include physical quantities such as emission spectrum,luminous efficiency,luminous time,and luminous decay time(Hu Mengchun et al.,2014).The scintillator's time characteristic is of great significance for the study of scintillator internal scintillation characteristics and scintillation detector research.There are also many methods for measuring the temporal characteristics of scintillators at home and abroad,and they are also improving and perfecting that change with each passing day.Based on the theoretical basis of the existing measurement methods,this article first briefly introduces the commonly used method of measuring decay time of scintillator,including the measurement of the time characteristics of inorganic scintillators and organic scintillators.Then,a new type of device for measuring the decay time of inorganic scintillator was introduced.This device is different from the existing scintillator attenuation time measurement method in its implementation.This device uses a fast current preamplifier to amplify the fast current pulse output from the scintillation detector,and then directly performs analog-to-digital conversion through a high-sampling-rate ADC(analog-to-digital converter).A large amount of ADC output data is sent to the FGPA for data reception and algorithm processing to realize pulse rising edge recognition and decay time calculation.Then the FPGA uploads the data through the HUSB chip.Finally,the device displays a distribution chart of the statistics of the decay time of the scintillator in the upper computer software.The X axis is the time scale axis,and the Y axis is each The cumulative count of decay time of the pulsed scintillator.Compared with the traditional measurement method,the device directly performs digital measurement according to the definition of the scintillator decay time,and the display result is a statistic distribution diagram of the decay time constant of the scintillator.Compared with traditional measurement methods,it is more referential,and the dynamic range suitable for light intensity is also wider.In the fifth chapter of this paper,actual tests were carried out to learn the scintillator decay time through inorganic scintillator manufacturer data manuals or domestic and international papers,and to verify the accuracy of the measurement results through an oscilloscope direct measurement method.The actual measured inorganic scintillators are LaBr,NaI,GAGG,CSI,and their decay times range from tens of ns to several thousand ns.This research comes from the national key R&D project "High-Resolution Airborne Gamma Spectrometry and Airborne Imaging Spectrometry Technology"(Question ID: 2017YFC0602100)and the National Natural Science Fund Project "Nuclear Pulse Signal Chain Mathematical Construction and High Speed Real-time Digital Research on Reconstruction Technology(Question ID: 41474159).The main research results of this device are:(1)An ultra-fast compound current preamplifier based on the principle of current shunt feedback(hereinafter referred to as the current type front)is experimentally measured to have a rising edge time of up to 2 ns and a bandwidth of approximately 500 MHz,and the experimental verification is 3.3uA-3.3mA.The fast current small signal in the mA range is linearly amplified with a linear correlation coefficient of 0.9999.(2)The device adopts the ADC+FPGA+HUSB architecture,completes the rotocol handshake with the HUSB chip in the FPGA,and realizes igh-efficiency data transmission,data processing.Simplified hardware ircuit design.(3)From the power integrity point of view,in order to achieve a high ignal-to-noise ratio and stability of the circuit.The design of the power upply topology is solved,and the power supply has a fast dynamic response, ow ripple and high efficiency,and the noise of the whole brother system is ontrolled within 5mV.(4)Developed the upper computer interface based on the drive library provided y Cypress and the Visual C++ 6.0 development language.(5)The measurement of the luminous decay time of four kinds of inorganic cintillators,LaBr,NaI,GAGG,and CsI,was tested on the waveform shape f the direct output of the scintillation detector and the statistical distribution f decay time measured by the device.