Triton identification in the Li-6(n, t)He-4 reaction measurement with the grid ionization chamber at CSNS Back-n white neutron source

The measurement of Li-6(n, t)He-4 differential cross section is the first experiment conducted with the Light-charged Particle Detector Array (LPDA) at the Back-n white neutron source of the China Spallation Neutron Source. The LPDA system consists of three kinds of detectors. One of them is the grid ionization chamber (GIC), which has the capability of particle identification. The particle identification performance of the GIC is presented based on the data collected in this experiment. Signals from the anode and the cathode of the GIC are digitized through the readout electronics and DAQ system. The offline data analysis is performed in two major steps. The first step is the processing of the original signal waveform digitized by the readout electronics. A set of digital filter algorithms including RC-CR filter, band-pass filter and digital CFD are developed and implemented in the original signal processing in order to obtain a high signal-noise ratio and a precise timing resolution. The second step focuses on the identification of triton events. The triton identification efficiency is measured to be 98% using a multivariate analysis algorithm implemented in the TMVA package in ROOT to discriminate the triton events and background events. In general, the performance of the GIC has met the baseline requirement of the experiment measurement.