We have done some more testing on the scintillator detectors developed by ISIS, UK these last few days. The aim was a “stress-test for the scintillator bank”, something quite popular these days. The previous tests (April) showed that the efficiency of the detector was some 80% of a standard 3-He detector (used to be approx 20% before these developments). We then also tried to determine the gamma sensitivity of the scintillator detector, which is/was ‘the other concern’ compared to 3-He detectors. We never seemed to manage to produce enough gammas to actually quantify that number.
This time we had the help of our radio protection service to provide us with some gamma sources that we would use to illuminate the detector while it was counting neutrons. Due to some technical and regulatory restrictions we have only determined the gamma sensitivity to be well below 1e-5 and probably below 1e-6. The reason for that is that you need so many gammas to get the damn detector out of balance. Eventually, taking the detector out of the neutron beam and putting the gamma source right in front of the detection surface, we got a hint of some ‘double counting’. The gamma sensitivity (in the no-neutron case) is approx 1e-8.
There’s still some analysis going on, but with these results so far, we can already conclude that this ISIS detector is very good alternative to an expensive 3-He detector! We now aim to have (a part of) the final detector ready for testing on our beam line within a year.
Thanks to Jeroen for the initiative! Thanks to the ISIS team for the collaboration!