On Shift: Ricardo Alarcon, Bill Franklin, Tancredi Botto here for afternoon
Data acquisition continued throughout the shift. We have been taking
fills to 90 mA with 60 sccm polarized hydrogen. Beam lifetime has been
very good (20-25 minutes) and halo is fairly low. ABS monitors have been
stable. Cell temperature has been about 96 K all shift. This is about 25
degrees warmer than where it was yesterday, but this was due to a change
in the heater set point by ABS group. Target polarization still flipping
between states 1 and 3 every 10 seconds. The BLAST power supply tripped
once at about 12:30. Ops made an access to the South Hall to bring it
back up while watching temperature sensors.
There were several more HV trips for the left sector wire chamber voltage
during the morning. In recovering from HV trips, a problem developed with
the BLAST beam gate. After at least one of the trips (probably dating
back to yesterday), the Data Acquisition Override switch was set to permit
(instead of OFF). This is not the correct thing to do, as it means that
data acquisition is not inhibited during Ring fills for either BLAST or
the Compton Polarimeter. Detector high voltages were still being ramped
down, but there was pollution of both event streams for runs up through
732 from this problem. Events were being acquired and the integrated
charge scaler for the Ring was incrementing during every fill. With some
effort, it should be possible to filter out the good data in replay from
the runs that were taken overnight and this morning (Tancredi is working
on this), but the asymmetry results aren't reliable at this point.
At this point, the beam gate problem has been corrected. Adam Degrush has
sent out detailed instructions for using the HV GUI to recover from trips.
After correction of the BLAST beam gate problem, the Compton Polarimeter
event transfer started to work. We are running the Compton DAQ on
dblast09 and broadcasting to the BLAST data stream.
Runs after 732 should be free of the beam gate problem. Plan is to keep
taking data.
-- ********************************************************************** Wilbur A. Franklin * Phone: 617-253-9518 Bates Linear Accelerator Center * FAX: 617-253-9599 P.O. Box 846 * Email: wafrankl@mit.edu Middleton, MA 01949 * **********************************************************************
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