RC report for 04/11 swing to 04/12 swing

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Log entry time 16:21:39 on April 12,2004

Entry number 82130

keyword=RC report for 04/11 swing to 04/12 swing

Run Coordinator's Report for 11 April Swing to 12 April Swing

Summary

LH2 production running. Problems with beam continue. Maintenance starts at 7am.

Significant News

IHWP now OUT.

The troubles with the beam seem to continue during the night although maybe on a less frequent level. This manifests itself in spikes in the halo rates, but they seem to go away as misteriously as they appear. The PD mentioned that this may be caused by problems the accelerator had with the RF. This will be checked and hopefully fixed during the maintenance period.

DMCH Interface box is the "new" box, and 120 Hz mode still does not
completely work for French electronics. A new procedure for 120 Hz running will be
to set acquisition mode to TS_Scaler rather than TS2_full. Jacques waits for a second replacement to arrive here today (Monday), which will have to be tested when it arrives.

We will be down for the rest of today and until tomorrow (Tuesday) evening. The current schedule is such that beam will be restored to the hall at 17:00-17:30. Shifts will therefore resume on Tuesday 16:00. The exact time of filling of the target and the ramp-up of the magnet will be announced as soon as we know the exact schedule of the accelerator.

Plans

Run Moller/IHWP insertion/Moller as soon as we get beam back

Continue with LH2 production running.

Run Moller/IHWP insertion/Moller Saturday morning at 8:00 (if we get beam back by Tuesday).

Deadtime study is planned, but depends on collaboration approval and the smoothness of the recovery from the downtime:

Another suggestion that was made was to demonstrate that the background
asymmetry underneath the elastic peak in the TOF specta is not an artifact of
some systematic dead time effect that is not being taken into account through
the Wells plot determination of the helicity correlated dead time, which does
a good job of correcting for the data inside the elastic TOF cut, but not as
well
for the inelastic proton TOF cut or the pion TOF cut. The asymmetry
of the inelastic protons at larger Q^2 are large and of opposite sign than the
elastic asymmetries, and could result in a sizeable correction in extracting
the elastic asymmetry. To demonstrate that this is a real physics background
and not a consequence of uncorrected dead time, we could take data at 10 uA
rather than 40 uA, in which case the dead time would be reduced by a factor
of four. To acquire the necessary statistics for a 4 sigma measurement would
require 24 beam hours (or two calander days, given a 45% efficiency). Due to
the large amount of time required to make such a measurement, I wanted to get
feedback from the collaboration, and would still recommend postponing this
measurement, should we deem it useful, until after we have surpassed 90% of
the statistics we expect to achieve for the entire forward angle mode of
the experiment.

Continue with LH2 production running until Monday when the accelerator shuts down again for the CD-0/DOE tour.

We are now on our official 3 day cycle for Moller measurements/IHWP
state changes.

Concerns

Spikes in French electronics

Non-statistical widths in detectors 13 and 14 of octants 4 and 8.

Non-understood influence of Interface Box to DMCH's. Spare does not work
in 120 Hz mode.

NA LTD errors still occurring at a small rate. Brian has generated a
"HowTo" document (located on the G0 web page under http://g0web.jlab.org/manual/Electronics_manuals.html)
for trouble shooting.