Measurement overnight

Start: around 1:00
Stop: 9:35
File: 161105_0935_BackgroundOvernight.root

The background level after removing the 252Cf source
from the hall dropped to 0.4n/s.

During the night there were neutron rates up to 120 n/s (see figure)

There is a huge spike in the rates which coincides with the time of 
LN2 filling. One can see spike in several spectra (not in all)
One can see also a structure superposed

The rate per rings is also shown. The outer rings see
a higher rate.

Also shown is the comparison of He107 one  (blue) of the outer ORNL2 tubes
with He084 one (red) of the inner ORLN2. The increase in count rate
is about 30%. 

Also shown is the comparison of two external tubes on the top and the bottom:
He107 (blue) and He137 (red), ORNL2 tubes.  There is no increase in count rate.

Also shown is the comparison of a tube above the lead shielding He028 (blue)
and behind the lead shielding He048 (red), UPC tubes. There is no difference.

There is also  comparison between the rate in the CLOVERS and BRIKEN.
Without beam the rate in the Clovers is around  100 g/s against 0.4 n/s in BRIKEN
At the maximum both rates are similar around 130 c/s.

There is also a plot of the gamma-neutron correlation.
We see that there are neutrons which are detected before
the gammas. A possible explanation several neutrons are produced
one is detected first the second later produces a gamma.