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Archived Messages for TAGGER@cebaf.gov: Participation

Participation

B. L. Berman (berman@gwis2.circ.gwu.edu)
Thu, 31 Jul 1997 10:19:37 -0400 (EDT)

Dear Collaborators:
There are two things to report:
1) The run has been postponed again, this time by only four days, to the
period August 18-September 4, with August 26-27 down for maintenance.
Although in principle this is enough time to finish commissioning the
Tagger and to run the photofission experiment, the recent history of the
accelerator (about 20% beam-on time) is such that we need to be very
careful how we use the time. This means that the items essential to the
experiment (such as the T-counters, and Total Absorption Counter) must be
done first, and others (such as getting the E-counters and the pair
spectrometer to work) may have to wait for another occasion. In any case,
this is the current schedule, and I again ask you to let me know ASAP
whether you will be at JLab for the run, and the dates. I'll reschedule
our (August 15) meeting to a slightly later date next Monday--probably to
August 18 or 19.

2) We made use of the very little time we had this last weekend
(something like 16 hours of the 64 hours scheduled) to understand the
major problem--the low tagging efficiency. It turned out to be severe
backgrounds in the T-counters, especially in the lower part of the focal
plane. Now we have seen efficiencies in the 80+% range, and are taking
steps, such as installing shielding, to improve things further. This is
the good news. The bad news is that the TAC was sparking, or at least not
working properly, and needs to be fixed. The other beamline devices were
not checked. Two radiator foils are now blown out and must be replaced,
and the collimator was found to be grossly misaligned and must be aligned
properly. Altogether, not such a bad weekend, despite the frustration of
losing so much beam time because of matters beyond our control.

Again, please let me know the dates that you can be in Newport News during
the August 18-September 4 period. [Also note that the Hall B
Collaboration Meeting is Sept. 5-6.] Thanks very much.

Cheers, Barry

Barry L. Berman
Professor and Chair
Department of Physics
The George Washington University
Corcoran Hall, Suite 208
725 21st Street NW
Washington, DC 20052
Telephone: (202) 994-7192
Secretary: (202) 994-6276
Fax: (202) 994-3001
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