Hello, All:
The goal of this shift was to determine whether or not the signal to noise
ratio in the chambers was decreasing over an extended time period.
Many files were recorded. The following files are all "good" files:
1892, 1893, 1894, 1895, 1896, 1898, 1900, 1902
All of the above files have roughly 20000 events in them (except for 1902,
which has only 10000).
After looking at the above data files, I can say that the signal to ratio
did not appear to decrease noticably. For most superlayers, it increased
slightly. Of course, it should be mentionned that, at the beginning of
this run, the gas mixture was changed from 80:20 to 70:30 He:Isobutane.
Increasing the Isobutane should cause the signal to noise ratio to
increase, so this was expected.
One superlayer (left sector, inner chamber, inner superlayer) had the
resistors going to ground removed in the hopes that this would help
increase the signal to noise ratio. According to these data files,
removing the resistor does help a little, but it certainly isn't a miracle
cure. (The signal to noise ratio in this superlayer was slightly higher
than that in the adjacent one.)
Another thing to note is that CODA seemed to hang much more frequently
tonight than any other night I've been on shift. I think 5 files out
of about 13 ended up hanging.
Another thing to note is that, after a fill, when the wire target was
being moved back in, the trigger rate would occasionally sky-rocket, even
though the wire was being moved back into the same place as for previous
runs. We decided that it might mean that the wire unit is still not
returning 100% to its desired position. Anyway, I found it must better to
move the target into -1.5mm, wait, and then step it into -1.3mm (which
seems to give a nice rate of about 30-40Hz).
A. Maschinot
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