The grounding problem 2 years ago showed up as wide pedestals, due to
AC noise on the signal cables. That problem did NOT make spikes in the
aDC spectrum.
karen
Adrian T Sindile wrote:
>
> 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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