Research And Design Of TPC Detector Readout Circuit With High Count Rate

The CSR External-target Experiment(CEE)is a charged particle spectrometer suitable for heavy ion collision and proton-heavy ion collision measurement in the energy region of the Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring(HIRFL-CSR).The main scientific goal of CEE is to perform the approximate full space measurement of charged particle products from heavy ion collisions in the CSR energy region,which will provides basic experimental data for the research of some important scientific problems:properties of compact celestial bodies,nuclear reaction dynamics,spin and isospin related nuclear force and equation of state properties of nuclear matter,QCD phase diagram with high baryon number density,etc.The spectrometer is composed of a number of sub-detector systems,among which is a large time projection chamber(TPC)read by the Gas Electron Multiplier(GEM),it has a high acceptance and can be operated under the high count rate(10kHz).This detector is used as the main track detector of CEE,and responsible for measuring the three-dimensional tracks of charged particles and performing particle identification.There are 15,000 readout channels in total.As a widely used detector,TPC has the ability of high-precision three-dimensional track detection,and can provide the momentum and energy loss information of particles for particle identification.Comparing with the traditional multi wire structure,Gem-TPC has obvious advantages in count rate and position resolution.Therefore,TPC detector based on GEM readout has become the first choice as track detector in the current major physical experiments.As the characteristics of high counting rate and large number of channels for the large area Gem-TPC,it puts forward higher challenges to count rate,integration,resolution,power consumption and other performance of readout electronics.The traditional readout electronics can no longer meet the application requirements and the readout electronics developed based on Application Specific Integrated Circuit(ASIC)chips come into being.It has become a trend to develop a new type of front-end readout electronics for GEM-TPC detector with low power consumption ASIC chips combined with field programmable gate array(FPGA).Based on the readout requirements of the GEM-TPC used in CEE,and also after researching and comparing several chips for the readout electronics of TPC detectors,the study of the new readout electronics system for high count rate TPC detector is conducted to choose an ASIC chip,named as SAMPA,as core chip in this dissertation.A readout electronics verification system with 320 channels has been developed,which features the characteristics of high count rate,high integration,high resolution and low power consumption.Mainly,the data processing module,a core unit of readout electronics system and data acquisition and processing software(in host computer)have been studied and designed,which provides technical reference and accumulation for the subsequent design of front-end electronics of TPC detector in CEE.The relevant test and evaluation of the readout electronics verification system has been implemented.For the read out electronics system,the root mean square value(RMS)of the baseline noise of each channel is less than 0.1f C;the inherent energy resolution of each channel is better than 1.3%(with an input charge of 70 f C);the non-linearity of each channel is better than 0.5%within the range of 2.2 fC to 99 fC.To combine the readout electronics verification system with a detector,the detection system has been checked with a ⁵⁵Fe source too.The energy resolution of the system is better than that of the commercial electronic system under the same operation conditions,and also system works normally at the event rate of 21 kHz.The test results show that the readout electronics verification system can meet the requirements of TPC detector for readout.