BigBite Wire Chamber Test

1
BigBite Wire Chamber Test
Wire chamber
Shower system
Optics Slot-slit

• Xin Qian
• Duke University
• Feb 20th
• For TRANSVERSITY
• Collaboration

Scintillator
Gas Cerenkov
Magnetic field shielding
2
Trigger for cosmic test
Front scintillator
Back scintillator
Computers,CODA
Forming Logic AND
cable
OR
VME
3
Wire Chamber
Low Voltage
HV for wire chamber
Threshold
4
Signal Output of Wire Chamber
Signal from cards
Level shifter cards
Long flat cable
VME
FASTBUS
5
Number_of_hits vs wire number
Reference channel

• 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
6
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
7
Second hit

• 10 T2
• Normal

8
Problems

• Everything looks normal, except the number of
  hits. (First noticed by Xiaodong)
• For run 249, we have about 10k trigger, number
  of hits on first plane is about 50k.
• Several possible reasons
• Threshold is too low
• High voltage is too high
• Ground problems?
• Other reason?

Big tail
RUN 249 X axis Number of hits per event
9
Threshold Change

• Did not see clear change in slope.

Lower threshold
Higher threshold
10
Threshold Change

• No clear change in drift time plot

Low Threshld
High Threshld
11
Threshold Change
Lower threshold

• Fewer second hit with higher threshold.

Higher threshold
12
Threshold Change
Lower threshold

• No clear change in correlation.

Higher threshold
13
Event Display

• See Xins webpage
• http//www.jlab.org/xqian/TRANSVERSITY/testlab/in
  dex.html
• HV is too high is ruled out.

14
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
  problems.
• 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 experts suggestions.

15
Acknowledgment

• Kalyan and Xiaodong (co-worker)
• Doug and Brad (useful suggestions, especially for
  OSP and telephone)
• Xiaohui (Making the initial analysis code)