Readout system for a prototype multi-purpose time projection chamber at CSNS Back-n

Abstract

This paper presents a readout system for a prototype multi-purpose Time Projection Chamber (MTPC), which is developed for the research of neutron-induced light-charged particles emission reaction. The prototype MTPC consists of 1521 readout channels for charge measurements, track reconstruction, and neutron time-of-flight measurement. The main function of the readout system is to perform 1521-channel waveform digitization based on multi-channel analog to digital converters (ADCs). Digital waveform compression, multi-board time synchronization, and many other efforts have been made to ensure system performance and stability. Test results show that the readout system has a time resolution better than 10 ns at a trigger rate of 20 kHz. With a 2.8 pC dynamic range of charge measurement, the noise without any input load is around 0.76 fC (in RMS), and the nonlinearity of each channel is less than 0.35%. A beam test with 6Li target has been carried out at the back-streaming white neutron source (Back-n) of China Spallation Neutron Source. The tracks of particles from neutron-induced reactions have been successfully reconstructed. The time-of-flight distribution of the 6Li(n,α)3H reaction reveals the resonance peak at about 240 keV. These results indicate that the readout system fulfils the requirements of the prototype MTPC.