The Development Of Readout Electronics System For The ?SR Spectrometer Prototype

The muon is one of the 12 elementary particles in the standard model.It was first discovered in 1936 by Carl D.Anderson and Seth Neddermeyer of the California Institute of Technology.A muon is a typical particle probe that extracts features such as microscopic magnetic or electronic environments in materials that are often difficult or impossible to obtain in other ways.The technique of injecting spin-polarized muons into a material material as a probe and then detecting their spin interaction can be called the ?SR technique.?SR technology has unique advantages in studying the microscopic magnetic properties of materials and complements other recognized technologies such as neutron scattering,electron spin resonance and nuclear magnetic resonance.The high-intensity muon source experimental device is a prerequisite for the study of ?SR technology,and high-power proton accelerators are required to generate high-intensity muon sources.Currently,only TRIUMF,ISIS,PSI and J-PARC in the world have muon source and conducts ?SR research.In China,because of the long-term lack of high-power proton accelerators,?SR research cannot be carried out.With the completion of the China Spallation Neutron Source,p.SR research has become possible.In 2015,the National Key Scientific Research Instrument Development Project"High-intensity Muon Source Key Technology Research" funded by the Natural Science Foundation plans to develop an experimental high-intensity muon source and a 128-channel ?SR spectrometer prototype on the China Spallation Neutron Source.The data acquisition system of ?SR spectrometer prototype includes front-end electronics and readout electronics system.This paper mainly completed the development of readout electronics system.Its main task is to measure the time difference between the arrival of the muon beam and the positron detected by the detector,and then upload the measurement results to a computer,and then convert it into a fixed format for analysis by specialized data analysis software.According to the characteristics and design goals of the pulsed ?SR spectrometer,the readout electronics system is divided into three parts,including readout(or TDC)module,fanout module and one set of data acquisition software.The TDC module is its core module and is responsible for time measurement and data uploading.By comparing multiple time measurement schemes,the method of multiple phase-shifted clock sampling in the FPGA is finally selected for time measurement to reduce resource consumption and increase the number of channels.A resolution of 312.5 ps is achieved by using 16 200 MHz phase-shifted clock sampling.A method for reducing the route skew of the input signal to multiple sampling flip-flops is proposed for the TDC design.The route skew of all TDC channel are less than 4 ps.Finally,32-channel time measurement,Gigabit Ethernet data transmission,and communication with 4 front-end electronics are implemented in a single FPGA.The fanout module is responsible for simultaneously fanning out the timing pulses output by the muon beam monitor to the four TDC modules.Data acquisition software is responsible for data acquisition,system control,data storage,and data format conversion.The dead time of the entire readout electronics system is less than 10 ns,the RMS time precision of the dual channel is less than 185 ps,the hit buffer depth of the single channel is 512,the time measurement range is 0-327.68 ?s,and the data transmission speed is up to 840.2 Mbps.This paper first introduces the basic properties of muon,the principle of ?SR,the construction status of muon source,and then introduces the design of ?SR spectrometer prototype.It focuses on the specific design details of the readout electronics system including TDC module,fanout module and data acquisition software.Finally,the important indicator test of the whole system is introduced.This paper has the following innovations:1.A low-dead time,large buffer depth,large measurement range,high-precision and multi-channel TDC module has been developed for the special requirements of the?SR spectrometer prototype,achieving 32-channel TDC design and Gigabit Ethernet interface design.2.A method to reduce the route skew of the input signal to multiple sampling flip-flops is proposed.The route skew of all TDC channels is less than 4 ps,which improves differential nonlinearity and integral nonlinearity,and solves the difficulty of clock phase.3.The ?SR spectrometer prototype data acquisition software was developed to realize data acquisition,system control and data storage.It supports NeXus data format and is compatible with Muon data analysis software commonly used in the world to meet the requirements of data analysis.