I had a conversation today with an engineer at Bicron regarding the suitability of plastic scintillators for neutron counting. I explained the the conditions of operation, ie, no substantial additional radiation other than background and residual radioactivity (especially true if one includes a lead shield around the scintillator), and basically single energy neutrons at about 3Mev. He commented that with a 2" X 2" scintillator and no discrimination, detection efficiency would be about 38%, and about 36% with an SCA set at a threshold of about 500kev. I would think that this setting would be sufficient to reject background noise from the PMT (~5,000 photoelectrons per second at room temperature!). One would still need to do a background count to account for cosmic and background radiation.
I asked him why one didn't see very many scintilator based neutron detectors, and we basically came to the conclusion that there aren't many situations that involve detecting neutrons without having to reject a lot of other accompanying radiation. He said that one common use of scintillation neutron detectors was is neuron time-of-flight measurements. I feel sufficiently encouraged by the above information to continue working on a plastic scintillator probe with integral preamp and SCA (maybe a HV supply too, if I'm feeling industrious). If I can persuade Ludlum to calibrate it, it would be interesting to compare it to my BF3 detector.
Created on Monday, May 07, 2001 10:17 PM EDT by Richard L. Hester