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User name A. Camsonne
Log entry time 02:40:29 on February 11, 2007
Entry number 192252
keyword=Dead time issue, checks summary
We still have an odd reading of high dead time for left arm.
The access allowed to check if there was double pulsing on T3, the signal
looked clean on the scope.
Checked the length of the busy signal about 100us with cosmics, 1 ms
reading all the VDC ( put threshold on VDC to 0 ) at a rate of 60 Hz.
So this should give a smaller deadtime value than what we read ( rougly
0.6 % and value on datamon was around 2% and about 6% with datamon
reading out about 45 % ).
Took a run with all T8 and pedestal subraction off (6177) at 1 KHz
deadtime was about 8% which is better than 25% with 500 Hz of T3.
I put back the FPP in the replay but it seems not data comes from FPP.
Looking at the THaNorma summary at the end of replay, the deadtime by
trigger seems to correspond to what we see online.
It looks the problem is bigger with lower ps factors, on B4C, with a
higher prescale factor the DAQ runs at about 2KHz with a DT of about 10%.
So this needs further investigation to make sure we can get the dead time
right and explain the high value we see, we might make another access
when if Bob has other checks he wants to do on the electronics.
Will try to think at other possible tests too.
A copy of this log entry has been emailed to: rom@jlab.org,doug@jlab.org,brads@jlab.org