Present at "weekly" meeting:
Doug Michael, Paolo Saggese, Erik Katsavounidis,
Chuck Lane (reporting), Hunmoo Jeon, Stefano Stalio
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One of the more disturbing occurances in the past couple of weeks has
been the discovery that one of our calibration lasers (SM2 bottom) had
"burnt up" in what appears to be a HV short in the plasma module. The
area of intense heat (melted plastic, charred insulation, etc) was limited
to a few cm^3 area, but the laser is now obviously unusable.
This particular laser was not yet put on the "laser control box", and
had been left on for long periods of time; Paolo observed that much of
the internal contacts had been corroded, as if it had been in a humid
environment, which he hadn't seen in our other lasers. Could this be
a laser from the old SM1 setup, from the days when the tunnel was humid?
There was also discussion on why fuses didn't blow and what could be
done to prevent a recurrance.
In other laser news, the SM3 attenuation setting was modified to
give higher light output; it seems that the laser is putting out less
light that it used to. This is also the case with the SM1 bottom laser.
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Erik, as usual, has been trolling through reams of data looking for
pecularities and finding good number of them. The latest efforts
involved comparisons of ERP, CSPAM, and HIPT triggers to try to find
inefficiencies. Naturally, he found some.
The vertical counters have a systematically lower efficiency in CSPAM
(~85-90%), while the N/S faces are very inefficient in the ERP. The
LUTs got the blame for that one. One short-term result is the
suggestion that CSPAM vertical counter thresholds be lowered by
approximately 20mV.
Paolo has also been comparing intra- vs. inter-uVAX CSPAM triggers, and
sees some (as yet unexplained) differences in a few channels.
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Your humble reporter has been putting FMT waveform plots on the 'web;
now running automatically. In addition, rate deviations detected by
the FMT rate monitor are also plotted and available on the 'web.
Point your browser to:
http://www.lngs.infn.it/www/htexts/macro/
or: http://duphy4.physics.drexel.edu/~lane/fastm/
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Stefano did a PMT gain survey, and found that the gains are generally okay,
with about 50 PMTs with noticable (but small, probably not worth fixing)
problems. All have good photoelectron peaks. We have 50 good spare PMTs.
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Hunmoo has been working away at the LED calibration system, modifying the
monopole calibration software for greater flexibility. There are still
some unresolved problems with the instability (at fractional % level) of
the LED fanouts, which makes it necessary to recalibrate the LEDs
immediately before using them for monopole calibrations. There was also
tuning (and fixing!) of the FMT calibration programs by YHR.
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There was discussion of an intermittant ERP supervisor problem, that
shows up in events where the same ERP tank appears two or more times.
There is speculation that it is a supervisor problem, and that as the
supervisors have moved around, the problem goes with them. It's now
in SM6.