Feasibility study on signal separation for spontaneous alpha decay in LaBr3: Ce scintillator by signal peak-to-charge discrimination

Abstract

A novel analysis method named peak-to-charge ratio (Vp/Qtotal) discrimination, aiming at background rejection especially for alpha decay self-activity in LaBr3: Ce scintillators has been developed. This method is based on a waveform analysis using the peak-to-charge ratio in the output waveform of a photomultiplier tube. The discrimination of alpha-induced events was achieved by using a threshold function based on the error propagation of the Vp/Qtotal value. The accidental rejection ratio of gamma-induced events was evaluated to be 0.17%. Furthermore, a total absorption peak spectrum processed with the Vp/Qtotal discrimination method for 68Ga 1.883 MeV gamma rays, where the energy was overlapped with background alpha events, reproduced exactly the same result as that of the background subtraction method. The difference in measured peak counts of both methods was 0.716%, and the statistical error in the Vp/Qtotal discrimination method and background subtraction was 4.81% and 8.70%, respectively. Thus a higher-accuracy measurement could be achieved using the Vp/Qtotal discrimination method. The present study demonstrates that the Vp/Qtotal discrimination method is a promising method for background rejection of the spontaneous alpha decay in LaBr3: Ce scintillators.