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Pulse pile-up identification and reconstruction for liquid scintillator based neutron detectors

2018    Luo, X. L.; Modamio, V.; Nyberg, J.; Valiente-Dobon, J. J.; Nishada, Q.; de Angelis, G.; Agramunt, J.; Egea, F. J.; Erduran, M. N.; Erturk, S.; de France, G.; Gadea, A.; Gonzalez, V.; Goasduff, A.; Huyuk, T.; Jaworski, G.; Moszynski, M.; Di Nitto, A.; Palacz, M.; Soederstroem, P. -A.; Soederstroem, P. -A.

The issue of pulse pile-up is frequently encountered in nuclear experiments involving high counting rates, which will distort the pulse shapes and the energy spectra. A digital method of off-line processing of pile-up pulses is presented. The pile-up pulses were firstly identified by detecting the downward-going zero-crossings in the first-order derivative of the original signal, and then the constituent pulses were reconstructed based on comparing the pile-up pulse with four models that are generated by combining pairs of neutron and.. standard pulses together with a controllable time interval. The accuracy of this method in resolving the pile-up events was investigated as a function of the time interval between two pulses constituting a pile-up event. The obtained results show that the method is capable of disentangling two pulses with a time interval among them down to 20 ns, as well as classifying them as neutrons or gamma rays. Furthermore, the error of reconstructing pile-up pulses could be kept below 6% when successive peaks were separated by more than 50 ns. By applying the method in a high counting rate of pile-up events measurement of the NEutron Detector Array (NEDA), it was empirically found that this method can reconstruct the pile-up pulses and perform neutron-gamma discrimination quite accurately. It can also significantly correct the distorted pulse height spectrum due to pile-up events.