Cluster Reconstruction And SAMPA Front-end Electronics Test Data Analysis For The CSR External-target Experiment Time Projection Chamber

Heavy ion collision has been the almost only method to study hot and/or dense nuclear matter in the laboratory.Studying the QCD phase structure and searching for the critical point is one of the most important target in the field.On the other hand,the equation of state of nuclear matter in the high baryon number density region is important not only for nuclear physics itself,but also for understanding the structure of compact stars.CSR External-target Experiment(CEE)is a spectrometer to study the properties of nuclear matter at high baryon density.Its main physics goal is to study the QCD phase structure and the equation of state of dense nuclear matter.The successful construction of the CEE will make it the first large nuclear physics experimental set-up working in the Ge V energy region in China.The CEE Time Projection Chamber(TPC)can reconstruct tracks and do particle identification,making it the most critical detector of the whole CEE set-up.TPC simulation and reconstruction software is a very useful fool for the development and optimization of the TPC hardware.TPC cluster reconstruction is the basis of track reconstruction,which is very important to achieve good tracking performance.Neighboring signals in the same pad row are first grouped together to form a2-dimensional cluster.Then a hit is created for each cluster at the ADC weighted average signal position.A cluster may also be divided into two or more hits,when the signal ADC vs.time bin has a peak-valley-peak structure,in order to obtain better two-track separation ability.Testing results using simulated signals show that the proposed algorithm has good position resolution and double-track resolution.When protons with the momentum of 0.5 Ge V/c go through the TPC volume along the z direction,hit position resolution in x and y direction can reach 0.1 cm and 0.043 cm.Double-track resolution at 90% can reach 1.1 cm and 2.8 cm in x and y direction.CEE TPC uses the state-of-the-art SAMPA electronics read-out chips with characteristics of high counting rate and continuous readout.The test and data analysis of this new electronic chip have been successfully carried out.Signal shape,energy and time resolution have been obtained,which provides important reference for the development of TPC electronic readout system.