Re: [BLAST_SHIFTS] summary 10-20

From: Adrian T Sindile (asindile@cisunix.unh.edu)
Date: Sun Oct 20 2002 - 20:11:30 EDT


Just a short comment...

> me and adrian started off with raising the HV. It became apparent
> that doing so immediately brings in a "spike" in some of the ADC
> spectra. This is not a pedestal and is clearly voltage dependent

Some of the PMTs had lots of extra voltage during the summer due to
imperfect gain-maching at that time. Nobody reported this behavior
(spikes for higher gains), and I personally have not seen it before.
In my opinion, the spike is still there for lower voltages, it is just not
obvious as it mixes with the ADC peak.
Two years ago, I think Karen explained to me something like this might be
caused by a grounding problem - but I do not want to advance another
hypothesis now, before we look more into this.

Adrian



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