BigBite Wire Chamber Test Xin Qian Duke University Feb 20th For TRANSVERSITY Collaboration Wire chamber Gas Cerenkov Shower system Scintillator Magnetic field shielding Optics Slot-slit

Trigger for cosmic test Front scintillatorBack scintillator OR cable Forming Logic AND VME Computers,CODA

Wire Chamber HV for wire chamber Low Voltage Threshold

Signal Output of Wire Chamber Signal from cards Long flat cable Level shifter cards VME FASTBUS

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

Second hit  10% T2  Normal

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? RUN 249 X axis: Number of hits per event Big tail

Threshold Change  Did not see clear change in slope. Lower threshold Higher threshold

Threshold Change  No clear change in drift time plot Low Threshld High Threshld

Threshold Change  Fewer second hit with higher threshold. Lower threshold Higher threshold

Threshold Change  No clear change in correlation. Lower threshold Higher threshold

Event Display  See Xin’s webpage  testlab/index.html 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 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 expert’s suggestions.

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