Subject: PMT gain reset in MACRO completed
From: Erik Katsavounidis (Erik.Katsavounidis@lngs.infn.it)
Date: Thu Nov 18 1999 - 15:05:08 EST
MACRO Colleagues,
The yearly PMT gain reset maintenance is now complete. A full set
of calibrations was performed today following a complete ERP LUT iteration.
The operation span over 5 (Mon-Sat of last week) + 2 (Tues+Wed of current
week) days and included swap of South face PMTs with Hamamatsus.
South face is not commmissioned yet though.
The PHRASE and ERP GC online monitor now run on the full detector.
As a general comment, we had to debug several counters (~50) where the
single photoelectron band was unacceptably broad, suggesting that PMTs
were running at different gains. This is quite relevant for doing fast
timing and we thus emphasized on nailing down such cases.
Overall though, the fact that we have been resetting gains looking at
two tubes at a time for the last 3 years or so is reflected in the width
of the spe bands of the horizontal counters: PMTs lose gain at different
rates and thus the spe pulses resulting from them diverge. Last time
we performed gain reset on a single PMT basis was in Nov 1996 and lasted
a good 3 weeks or so, something though that I don't think is worth investing
for the next 6 months or so of MACRO's data acq.
Gain loses were typical as with previous year with mean voltage increase
at the level of 15V. Nicola is working on preparing some summarizing
plots similar to ones of prev years that will soon appear on our web site
(http://wsgs02.lngs.infn.it:8000/macro/ --> hardware info --> PMTs).
Alec, Ioannis, Massimo, Nicola and Roberto have all done a great job
in delivering this year's PMT maintenance operation in a timely and ordered
fashion. What worth mentioning is the fact that the PMT work had to be
interrupted twice due to power failures in Hall B (I've lost counting
of these...) with an appreciable amount of effort going into guaranteeing
the detector is properly shut down and then up.
Regards,
--Erik Katsavounidis
This archive was generated by hypermail 2a24 : Thu Nov 18 1999 - 15:05:14 EST