multiple pulsing T1,T2

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User name R. Michaels

Log entry time 20:36:48 on May 7,2009

Entry number 271573

Followups:

keyword=multiple pulsing T1,T2

I went in the hall to look at what Bo and Vince were doing.

It seems we have multiple-pulsing on T1 and T2 (~6% and ~20%
probability each) at the scaler. It's likely this percentage
remains stable with beam on, but it can be checked by plugging
these into a multihit TDC with 2 usec range. This hypothesis
would imply an artificial deadtime enhancement of 6 and 20%
resp. for these 2 triggers, which could be corrected by this TDC.

Therefore if you have ps1=1 and ps2=infinite and run with beam and
you see "15 %" deadtime it is actually 15 - 6 = 9 %. (something
like that)

The reason T2 is worse is that it's a looser trigger.

I suggested to Vince & Bo to plug these triggers into a TDC
and continue running. Ultimately we may want to replace more
PMTs to eliminate the double-pulsing. The PMTs may be damaged.
I suppose it should be checked more carefully that this is
indeed the culprit, but it seems very likely to me.