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

Wire ChamberHV for wire chamber Low Voltage Threshold

Signal Output of Wire ChamberSignal from cards

Long flat cable Level shifter cards

VMEFASTBUS

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 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

Threshold Change

Did not see clear change in slope.Lower threshold

Higher threshold

Threshold Change No clear change in drift time plotLow 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 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.

Acknowledgment

Kalyan and Xiaodong (co-worker) Doug and Brad (useful suggestions, especia

lly for OSP and telephone) Xiaohui (Making the initial analysis code)