No fast neutron counter on the planet exceeds about 3% absolute efficiency. For thermal neuts effeciencies can approach 25% in special proportional counters.
I think Joe was looking at the multiple secondaries giving a statistical boosting which is rather scattered at low flux rates in plain scintillators. Such systems are never, ever used by the pro's for any purpose involving neutrons due to this very phantom like boosting. It can't really be discriminated out either. Again, it's why the big boys shun the system when looking at real neutron counting.
If the straight plastic proton recoil system was viable in a scientific sense, the Bicron BC-720 special fast neutron scintillator would never have been brought into existence.
many, many proton recoils in a straight scintillator look just like the light flash from a 20kv x-ray!! Joe used little or discrimination in his system.
The BC-720 will do the same thing and will, if not discriminated, count just like Joes counter. (thosands of counts both X-ray, Gamma, ultra heavy Beta, Cosmics, and all proton recoil quanta.) The encapsulated target rings of ZnS/(Ag) change all of this. Only those few ultra heavy Fast neutron induced proton recoils in the vacinity of the rings will hit active phosphor sites creating 2 order of magnitude greater quantum events over the din of other "in scintillator" nuclear activity. These signals are so huge that discrimination is a child's play effort. I have studied this at length on my two systems here with my digital storage scope. Still, the best scintialltor efficiency known for fast neuts over 2mev is obtained with the BC-720 at ~0.6%.
Richard Hull
Created on Thursday, May 03, 2001 2:20 PM EDT by Richard Hull