scint signal quality on R-HRS looks ok to me

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User name R. Michaels

Log entry time 16:59:20 on November 04, 2009

Entry number 297391

keyword=scint signal quality on R-HRS looks ok to me

I looked at the scintillator signals on a scope on R-HRS and they
all look normal / good to me. Very little after-pulsing. By the time
the trigger is formed, there is NO after-pulsing in the trigger, the
main thing we care about. It looks like Bogdan's repair work is fine.

I think the reason the TDCs look "funny" may be that for 90% of our
history we ran with single-hit TDCs (1875) which by definition cannot
show after-pulses. Now we run with multi-hit TDC (1877) which shows
after-pulses if they exist. On a scope these after-pulses were very
small in amplitude -- probably not the usual mechanism. They would
be cut with a higher threshold, but I don't think we care as long as
our efficiency is high and the rates per tube are not too high (50 kHz)

My suggestion for tonight's checkout would be to verify that the
"trigger logic is satisfied". That means that when you have T1 trigger
you see a hit within a cut of each TDC normal peak, and there is a
hit on each of 4 PMTs (2 from S1 and 2 from S2). You can also look
for weirdness like having hits in VDCs far away in time (~400 nsec)
from the VDCs that may be caused by a T1 that "jumps in time". Be sure
to look on a broad timescale for VDCs (tight histogram limits would
artificially suppress this problem).

Eventually we need to know the scintillator efficiency -- a standard
analysis. If that's 98% like it normally is, I think we're done.

A copy of this log entry has been emailed to: vasulk,bogdanw