Beam tuning in BigRIPS

At 19:00 access to Exp. Area was closed and the tuning
of BigRips started.

Unfortunately the 252Cf was left on the table close
to the stairs and cannot be removed until 23:00.

We did a background measurement
Start: 19:00
Stop: 22:18

File: 161104_2218_BeamTuning.root

In the attached figure 1 one can see a plot of the rate
(neutrons/10s) in the BRIKEN detector during this time
The rate was at high as 150n/s during this period.
We estimate that the influence of the 252Cf source is about 15n/s
(corresponds to the lowest rates)

Also attached are pictures of the Top and Bottom plastic veto detectors
mounted just above and below the hole in the shielding.
Interestingly the bottom sees less counts at high energy
and this could be related to the 10cm lead wall raised
before the degrader to protect AIDA that covers only partially 
the top detector.

Also attached is the neutron spectrum for the different rings superposed.
(ROOT color code)