Pulse Shape Discrimination in Impure and Mixed Single-Crystal Organic Scintillators

• Published in: IEEE transactions on nuclear science Vol. 58; no. 6; pp. 3411 - 3420
• Main Authors: Zaitseva, N., Glenn, A., Carman, L., Hatarik, R., Hamel, S., Faust, M., Schabes, B., Cherepy, N., Payne, S.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2011; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Computer simulation; Crystal growth; Crystals; Decay; Diphenylacetylene; Discrimination; Impurities; neutron detector; Neutrons; Organic materials; organic scintillators; Percolation; Pulse shape; pulse shape discrimination; Scintillation counters; Shape; Single crystals; stilbene
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2011.2171363

Neutron/gamma pulse shape discrimination (PSD) utilized for detection of high-energy neutrons with organic scintillators was investigated using a model system of mixed diphenylacetylene-stilbene single crystals of different compositions. The results of the studies, which include experimental tools of crystal growth and characterization combined with computer simulation, showed that the presence of impurities with lower bandgap energies can be a major factor influencing PSD properties of organic materials. Depending on the concentration, an impurity may suppress or increase the rate of excited triplet state interaction leading, respectively, to a complete disappearance or enhancement of PSD, consistent with a percolation threshold. The results are applied to produce novel materials with controlled decay characteristics. Single crystals with a large fraction of delayed light and enhanced PSD have been grown for high energy neutron detection, while crystals with suppressed delayed light were produced for use as low-afterglow scintillators for energetic neutron detection in time-of-flight experiments.