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

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2018-07, Vol.897, p.59-65
• Main Authors: Luo, X.L., Modamio, V., Nyberg, J., Valiente-Dobón, J.J., Nishada, Q., de Angelis, G., Agramunt, J., Egea, F.J., Erduran, M.N., Ertürk, S., de France, G., Gadea, A., González, V., Goasduff, A., Hüyük, T., Jaworski, G., Moszyński, M., Di Nitto, A., Palacz, M., Söderström, P.-A., Sanchis, E., Triossi, A., Wadsworth, R.
• Format: Article
• Language: English
• Subjects: Digital; First-order derivative; Instrumentation and Detectors; Liquid scintillator; Neutron-[formula omitted] discrimination; Neutron-gamma discrimination; Physics; Pile-up
• ISSN: 0168-9002; 1872-9576; 1872-9576
• DOI: 10.1016/j.nima.2018.03.078

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 γ 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 γ 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-γ discrimination quite accurately. It can also significantly correct the distorted pulse height spectrum due to pile-up events.