Notes from Meeting Mar 27, 2009

• Compton Electron Detector

• Data taken with source in 2 plane coincidence trigger where one of the planes is the last one. Signals in the remaining 2 planes suggest a 10% efficiency.
• There is no signal when the source is absent.
• Various suggestions as to how to proceed:
  • speak to engineer about getting access to the analog signal.
  • try to decouple the detector and trigger electronics to find bugs in the logic.
  • check range tables or Geant4 simulation to get expected ionisation in each plane.
  • look at data in singles mode (need to disable some strips to minimise noise) to check for ETROC logic or timing problems
  • use different bias voltages to check thresholds
  • look at logic signals on scope (requires LDVS to NIM converter)

• Nonlinearity of PMTs at CMU

• Megan reported on studies using two LEDs, one with fixed brightness and the other variable. The previous cross talk problems have been resolved.
• The results suggest a 2% nonlinearity up to 36 MeV.
• Next step is to prove the effect by using different voltages and tubes.
• A more robust system will be built for travel to JLab.

• ADC Testing at JLab

• Luis is working on a more precise local fit, plotting slope vs signal

• Simulations

• Dustin showed target theta and phi comparisons. The theta agreement is better than phi.
• Dustin will try the collimator cut
• There was discussion on the angular resolution for the HRS + septum, it was suggested to study seive slit data.
• Bob reported that we can use the old seive slit in the experiment if a few extra holes are added. This design would give 3 mr for a point target which should be resolvable.


Comments to: Bob Michaels