After spending some time checking the slit position data against previous
numbers we intended to proceed with the retiming (which should only take
one shift). The start counter signal for both upstream and downstream
tubes was missing from the scalers.
After checking if proper hv was applied we went to the D-tunnel to check
the scope. No raw signal appeared for either top or bottom start counter
tubes on the scope.
Looking at the dumb terminal we saw that one tube was drawing a fraction
of the current as the other indicating something less than an open
circuit.
Requested an access and found the downstream start ctr hv cable to be
coming apart at the connector. As access was difficult we started to move
the subframes apart - but decided against it as we soon figured we could
manage we only moved the R subframe out about 2" and then back to the
stop *****PLEASE CHECK THAT THE SUBFRAME IS PROPERLY POSITIONED BEFORE
TURNING ON B FIELD****
We connected a new hv cable to the downstream tube and saw signals from
both up and downstream with a scope in the pit. Back at the D-tunnel we
still saw no signals from the start ctr signal cables.
We found that the signal cables from the start ctr pmts were good at the
patch panel as we saw signals there. After further investigation we found
the D-tunnel start counter cables to be very flaky and only passing a
signal when physically manipulated but the behaviour was unpredictable.
To save time we brought a ladder to the pit and connected the start
counter signal cables to LTOF15top and bottom and finally saw signals in
the D-tunnel and on the scalers. The summary of connections is:
Cable# Comments
170 Bad HV cable - was START downstream hv
159 new hv cable to replace 170
16 new downstream START signal - was LTOF15B signal
127 new upstream START signal - was LTOF15T signal
Beam returns at 23:23
-Start Counter is back (in LTOF15) and HV is off on LTOF14
-seeing periodic fluctations in overall rate by a factor of 10
-started run 2375 with trigger:retime_right_l16.settings
Pete and Nik
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Pete Karpius
Graduate Research Assistant
Nuclear Physics Group
University of New Hampshire
phone: (603)862-1220
FAX: (603)862-2998
email: karpiusp@einstein.unh.edu
http://pubpages.unh.edu/~pkarpius/homepage.htm
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