We took a couple of cosmics runs at the beginning of our shift just to make
sure everything was stable. The TOF gains look all right (the few that are a
little off seem to be like that because of statistics - this was our
conclusion after comparing with runs taken yesterday).The 4 "hot" channels
that gave us jumpy pedestals are still a bit of a mystery: 3 were looking
about like yesterday, one moved again...
We did not update the blast.sc_cal, as 60 out of 64 channels are stable and
the remaining 4 seem to jump around anyway. We need to understand the reason
of this. In the end this will automatically be taken care of as the MySQL
database allows us to record thresholds and pedestals for every run.Plots
from those two cosmics runs are in the logbook.
For the wire chamber,a relatively large data sample (650 k) was obtained for
a single gas (1 sccm) and threshold voltage setting (2V). The runs # are 2743
and 2744 and the trigger =elastic_coincs_front4.settings. Increasing the
threshold voltage seemed, at least globally, to decrease the
signal/background . Therefore we focused our attention elsewhere and out of
curiosity spent the rest of the time investigating the effect that including
cerenkovs in the trigger had on the ratio of good ep tracks to number of
events. We only considered geometrically which CC and TOF combination to use
and realize this probably rejects a fair number of good events. However we
were only interested in getting a cleaner sample of ep events than only
including TOF's (right now less than 1 in 1O appear to be ep events as seen
using nsed). The first change was to only include X's for those cerenkovs
that blocked the front 4 TOF's geometrically (the the first cerenkov) and put
0's everywhere else. As expected this did not change the rate dramatically.
The second test was to include the cerenkov coincidences in the trigger
(elastic_coincs_front4Improved_CC.settings, "Improved" is in quotes). This
was done by requiring a cerenkov 0 fire for the forward TOFs (0-3) ,
requiring no cerenkov hit for the back 8 TOF's and either CC #1 hit/no hit
for TOF's 4&5. With this trigger the "ep tracks" seem to occur in about half
the events, although for some reason the tracks looked noisy, a lot of
uncorrelated hits. This is probably unrelated to the trigger change ,but
since our shift came to an end we didn't have time to investigate this
further.
Adrian and Adam
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