Because is something wrong I decided to measure the counts rate as function of threshold energy. Maybe my threshold was incorrect.
Below are my results for n's detector with HAMAMATSU PMT (-1500 V):
So it looks like my previous threshold value (-500 mV) was not good. Let's set it up the -200 mV. And let's see does the n's detector sensitive to the source. The same set up and distances as before.
|counts/sec (5 min test), no source||counts/sec (5 min test), with source on the top of PS1|
|n's||19.890.26 (total 5966 cnts)||58.840.29 (total 17652 cnts)|
So now we see the source. The ratio are: