PMT gain re-setting to be done next week

MICHAEL@axpgs2.lngs.infn.it
Wed, 8 Nov 1995 11:16:56 +0100 (WET)

Next week is a scheduled down week for MACRO data acquisition. We plan to
take advantage of this week to address many PMT problems/low gains which have
developed with time. I have recently done a sampling survey of the PMT gains
throughout the detector and find that there are many tubes which are now giving
less than 3.5 mV/SPE. In addition, there are perhaps 10-20 tubes which have
wrong gains set on at least one tube and a few other tubes which are noisy
in the monopole trigger.

Clearly, this activity will require resetting of the software thresholds
in PHRASE and ERP. I hope that this will in fact solve a number of problems
with low threshold channels in the ERP. Please be prepared to assist us
next week by running programs to determine the new software threshold settings
and new calibration files using the new gains.

We will not change the gains on all PMT's. If a PMT has an apparent gain
setting giving at least 3.7 mV/SPE, no action will be taken on that
tube/tankend unless one or both of the tubes appear to be set with an
anomalously high gain or other problem is present. We will undertake this
work on a one SM at a time basis and proceed as far as the down-time permits.
If we can complete the work on the entire detector, I expect that it will be
at least 6 months before it will be necessary to again take this action.

Please let me know any suggestions or feedback on this plan.

Doug