KEK Cosmic Tests Run Status + Summary Dan Burke 22/01/06

Outline jCF4 measurements and tracks Energy resolution comparisons Gain measurement Summary of jT2K gas data Results for jT2K gas [Ar jCF4Iso ( )] Conclusions and future plans

jCF4 – AfterPulses With the ArCF4 we found afterpulses similar to the October results (*picture from Oct.)

Adding isobutane improves stability, stops after-pulses, and improves resolution on 55 Fe Ar+jCF4 3% jT2K gas Comparison

Gain for the T2K gas RUN at 340 V Gain ~ 4000

Run Summary jT2k V/cm  ~13k events  60-70% good events jT2K 80 V/cm  Currently 2200 events  ~400 events/h  Continuing run until tomorrow afternoon (~10k events)

Track Drift Distances

Phi Distribution Distribution Used

Sample Tracks – T2K Gas 186.7V/cm

Drift Velocity Gas V drift (cm/  s)Magboltz(cm/  s) ArCF4Iso V/cm (preliminary – possible faster than expected -or- not full drift length 7.4 ± ± 0.003

Conclusion Great results so far, isobutane has eliminated the afterpulses Lots of data for T2K gas at two drift fields Continue with readings until tomorrow afternoon Change HV power supply with a KEK supply  Take more data after we leave Analyze results