T2 double pulsing problem solved

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User name Moffit / miham

Log entry time 15:55:53 on May 19, 2009

Entry number 274812

keyword=T2 double pulsing problem solved

Today during the access Bryan and myself went down the hall
to solve the problem with T2 double pulsing in the HRS-L
scaler. We tried various things in order to solve the problem.
First we were swapping the channels (cables). At one moment
problem seemed to disappear. However after few minutes the
double pulsing reappeared. In the next step we unplugged
the T2 and T6 scaler signals from the trigger electronics and
plugged the 1kHz pulsar directly into them. When we checked the
the scaler rates in HRS-L and Bigbite GUI, they matched. We were
clueless. Since everything seemed to be working again, we plugged
all the channels back to the original configuration, but once we did
that double pulsing again came back. After that we have decided to
change module LeCroy 4616 with equivalent Phillips module. First
it seemed that this helped but when we plugged-in all the channels,
the problem came back. At that point Bryan realized that when he unplugs
the T1, the problem disappears. He suspected on the cross-talk between
the T1 and T2.

After we realized what the problem was, we went up into the HRS-L and
played with the cables a bit. We localized the problem to the Daisy chain
ribbon cable leading to the scalers. When all the connectors were
plugged into the modules the T2 was double pulsing. If Bryan unplugged
one of them (it did not matter which one) the problem disappeared. At
that point we have decided to change this cable. We made a new ribbon
cable, tested it, and plugged it into the scalers. After that, problem
seemed to go away. Now (at least with the single frequency pulser)
all scalers look fine.

A copy of this log entry has been emailed to: moffit, miham, sirca