As it was advertized at the Lecce collab meeting, we've started
today resetting PMT gains in MACRO. SM1/2 are the first in line
and we expect to be ready for re-commissioning sometime tomorrow.
We expect to continue at the same rate, i.e. one uV every two days.
For your records, RUN#16787 was the last full MACRO run taken with
the old gains.
Let me remind you that it's been a year since the last PMT gain
reseting operation. Since then gains have drifted by 10-25% in
20-30% of the counters. Maintaining gains and PMT quality at their
best is crucial for the wide spectrum of sensitivities we are
addressing in MACRO.
The same procedure as last year will be followed; i.e., gains will
be reset by eye, one PMT pair (for horizontals) at a time, while
gains on individual horizontal tubes will be set only if split gains
is suggested. Individual tank-end work will proceed in parallel with
the gain reseting; however, if found necessary, it will be left for
after the commission of the bulk of each SM/uVax.
Threshold adjusting for the ERPGC and PHRASE will be inevitable,
both of which we expect to be managed locally at Gran Sasso.
Thanks,
--Erik