The Design Of Front-end Electronic Prototype For MuSR Spectrometer

Ever since the invention of the optical microscope,scientists have developed a lot of advanced technology to detect the microstructure of matter,such as X-ray diffraction,electron microscopes,neutron scattering etc.Like the electrons and neutrons,the muon is one of the most basic particles in nature.The ?SR(Muon Spin Rotation,Relaxation and Resonance)technique is a collection of methods that uses the muon spin to look at structural and dynamical processes in the bulk of a material on an atomic scale.At present,?SR techniques are widely applied in condensed matter physics and chemistry.Especially in recent years,researchers use the ?SR technique to study the inner structure of samples in the field of HTS(High Temperature Superconductor).In 2015,the IHEP plans to build an experimental muon source at China Spallation Neutron Source(CSNS).It wil]provide an excellent platform for the applications based on ?SR techniques.The project plans to develop a 128-channel positron spectrometer prototype,including detectors,electronics,data acquisition systems,sample chambers and magnetic devices.This paper mainly completes the design of the front-end electronic prototype for ?SR spectrometer.In order to improve the integration density and timing accuracy of circuit,non-delay-line CFD timing circuits are applied to realize 8 constant fraction discriminators on a single-width NIM module.We have designed special circuits to convert ECL to LVDS,thus the outputs of timing signals are LVDS compatible.Including DAC outputs,analog switches and the communication with the TDC board,the entire front-end electronic prototype is controlled by a Cyclone FPGA.Key features of the system are as follows:adjustable lower-level thresholds,adjustable time walk,self-test and calibration.The test results show that the time walk is less than 255ps,and the timing error is about 55ps when connecting to the detector.Compared with the 600ps timing error of the back-end TDC,the timing error of the front-end electronic prototype can be ignored.In recent years,SiPM is of great interest in nuclear detection,due to its unique advantages,such as high photon detection efficiency,compact,insensitive to B-field and low cost.Based on the prototype design of front-end electronics,we further make a research on the properties and performance of SiPM and the design of its readout electronics.At the beginning,this paper introduces the background of the project,basics of the ?SR spectrometer,the design of the positron spectrometer prototype,and various timing discriminators.The design of the front-end electronic prototype for ?SR spectrometer and the test of important indexes are introduced emphatically.In conclusion,for the PMT solution,the front-end electronic prototype has achieved its original goal;for the SiPM solution,this paper has finished a lot of useful preliminary exploration.The main contributions of this paper are as follows:1.We have completed the design of the front-end electronic prototype for ?SR spectrometer.The test results show that the timing error of the front-end electronic prototype which is based on non-delay-line CFD is about 55ps.With the advantages of high integration density and low timing error,the prototype has reached the requirement of the ?SR spectrometer system.2.Based on a thorough investigation of the properties and performance of SiPM and its readout electronics,we have completed the selection of key devices and preliminary design of electronics for the SiPM-based positron spectrometer.