this shift was mainly spent trying to fight the WC's space charge effect.
right from the get-go, we noticed that while the left WC sector
superlayers all had good, constant signal-to-noise ratios of 3 or 4 to 1,
those in the right sector were poor (as bad as 1 to 1) and were not
constant.
so we zeroed the WC high voltage for an hour (actually closer to two
hours) and had CCR not play with the beam at all. twice in this time
period, we brought the WC high voltages up and did a quick 3-minute cosmic
run to see if the signal-to-noise was any better.
we took a few more runs. initially, all the superlayers (except
right-side, middle-chamber, outer-superlayer) all seemed fine (with
signal-to-noise ratios of at least 2 to 1). however, within about
20minutes of taking data, 5 of these 6 superlayers' ratios had fallen
below 2 to 1. within another 10 minutes, many were very close to 1 to
1.
so another hour break.
afterwards more data taking. but the space charge effect appeared within
about 10 minutes of beam time. i logged in the logbook a chronological
accounting of the signal-to-noise ratios.
for the few runs we did manage to take, nsed said that they were all crap
pretty much; tracks were rare indeed.
another hour break at 7:00am. the next crew should have "fresh" chambers.
also, the compton laser tripped around 4:00am or so. we couldn't reach
bill, and we didn't know how to reset it (or even if you could without an
access).
aaron and wang
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