Doug and Tavi on shift.
Previous shift had trouble with the ABS and Vitaly was heating up the
nozzle and then letting it cool down in preparation for more running with
polarised hydrogen.
While that was going on Tancredi was analysing the calibration of the DCCT
to determine a new current or charge calibration based on the run 291 which
Vitaly and I made. This was done and the results are in the log book but
the calibration function needs to be installed into the analysis programs.
At about the same time we noticed that the beam gated rates in the scaler
display were greater than the ungated rates. Since this seems wrong
Tandcredi investigated the scaler module and replace one module and
corrected a bad connection. Scalers were behaving more reasonably after
that. However, this implies that the DCCT calibration needs to be redone
as the scaler values may be different now. So next time Vitaly is in (he
knows how to drive the calibrated charge source) the calibration run should
be repeated.
The BAS nozzle temperature did not on its own return to reasonable values
however, Ernie phoned in and suggested that the vacuum was bad. Since we
can't check this with the toroid on we ramped down the toroid and had a
hall access. One of the turbo pump power supplies had failed so the
roughing pressure was back streaming through that turbo pump and ruining
the ABS vacuum. I closed the roughing valve and the pressure started to
improve.
Nozzle temperature on the ABS improved and we were able to turn it on to
nominal flow and power. We then started running with polarised hydrogen
for the remainder of the shift.
Plan is to run polarised hydrogen, flipping between spin states 1 and 3
every 20 seconds within a run and flipping beam polarisation each fill. Now
that the scalers are working properly and once we get the new calibration
these runs can be analysed for asymmetry.
Sunday we will switch to unpolarised hydrogen and load the neutron trigger
and collect some background rates before switching to unpolarised deuterium
and finish this run period looking for neutrons.
Cheers,
Douglas
26-415 M.I.T. Tel: +1 617 258 7199
77 Massachusetts Avenue Fax: +1 617 258 5440
Cambridge, MA 02139, USA E-mail: hasell@mit.edu
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