05/11/2011 neutron detector threshold calibration

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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	19.89[math]\displaystyle{ \pm }[/math]0.26 (total 5966 cnts)	58.84[math]\displaystyle{ \pm }[/math]0.29 (total 17652 cnts)

So now we see the source. The ratio are:

[math]\displaystyle{ \frac{Rate_{source}}{Rate_{w/source}} = \frac{58.84}{19.89} = 2.96  }[/math]