bigbite wire chamber test xin qian duke university feb 20th for transversity collaboration wire...
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BigBite Wire Chamber Test
Xin Qian
Duke University
Feb 20th
For TRANSVERSITY
Collaboration
Wire chamber
Gas Cerenkov
Shower system
Scintillator
Magnetic field shielding
OpticsSlot-slit
Trigger for cosmic testFront scintillator Back scintillator
ORcable
Forming Logic AND
VME
Computers,CODA
Number_of_hits vs wire number
Flat structure suggests no local problems except two broken cables.
The structure of the hits pattern is due to the trigger setup.
Two bad cables
Reference channel
Drift time for the first time
See a clear drift time Most of T2 is out of T1 main peak. T1 is the time for first hit on this channel
(wire) T2 is the time for the second hit on this
channel.
t1
t2
Problems Everything looks normal, except the numbe
r of hits. (First noticed by Xiaodong) For run 249, we have about 10k trigger, numb
er of hits on first plane is about 50k. Several possible reasons:
Threshold is too low High voltage is too high Ground problems? Other reason?
RUN 249
X axis: Number of hits per event
Big tail
Event Display
See Xin’s webpage http://www.jlab.org/~xqian/TRANSVERSITY/
testlab/index.html “HV is too high” is ruled out.
Conclusion Data was taken for first wire chamber using front
and back scintillator coincident trigger. Data was recored using VME TDC. Drift time & hitting pattern suggest no local proble
ms. Do see a problem with more hits than expected.
(Not a VME problem, see the same thing on FASTBUS)
Rule out threshold, HV or any local problems. Reason is not clear at this stage
Ground issue? Flat cable? Need expert’s suggestions.
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