[BLAST_SHIFTS] Shift summary 08/16/2003 Swing

From: Electronic Log Book (elog@blast05.lns.mit.edu)
Date: Sat Aug 16 2003 - 23:42:49 EDT


Operators: alarcon kohlm yxiao

This is my shift (but not shit, see Ricardo's message) report (16-24).

We went on taking polarized hydrogen data, flipping helicity after each run.

Runs 1997 - 2013 taken and crunched.

The Compton data acquisition was invoked with every run. However, there was no clear indication of a Compton signal when TZ called in at about 7pm. The Laser+Background rate was almost equal with the Background rate about 400. The beam position on LPM29 showed x=-6.51 and y=-1.93mm.
Probably the misalignment arised from retuning the beam once after Genya's message from Friday night.
I did a laser scan, however within the scanned square of 20x20steps no real enhancement of the laser signal was found. I tried then manually, and found a nice S/N of 1600/mA / 400/mA after moving mirror 2 X by +17 and Y by -20 steps.
I checked the automated result of the Compton measurement for runs 2001 and 2012 and found P=+1.03+-0.03 for lambda/2 IN and P=-0.22+-0.05 for lambda/2 OUT (viz. attached plots).
Conclusion: Beam is polarized as the P's flip their sign. Interpreted as beam polarization, the unphysical value P=1.03 as well as the difference indicates a false asymmetry.
If the polarization is assumed to be the same for both helicity states, it could be deduced as 0.62+-0.08.

The beam should be tuned (tomorrow) such that it is centered on LPM29, too, in order to maintain alignment of the laser with the collimator.

Run 2009: CCR called and said that for the first fill of this run he had put the waveplate out after the fill instead before. Though the helicity bit for the first fill may indicate IN though it was out in fact, like for the rest of this run.

Crate R2 tripped approx. once per hour, with decreasing tendency.
Compton DAQ often tends to kill EtSpy, making frequent Coda restarts necessary. Happened every other run in the beginning of the shift, became more silent later.

MK



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