Notes from Local Meeting on May 14, 2003

• Lumi (Bryan)

  • Second Lumi at small angle is being commissioned.
  • Pedestal Noise from Long Cables from Hall to Counting House appears to change with time (depending on time of day, ranges from 20 to 60 adc channels).
  • Planning to install a Lumi detector in the Right Spectrometer Hut with short cables to measure pedestal noise to compare to long counting house cables, during Energy change on Thursday (May 15th).

• BCM and Charge Asymmetry (Kent)

  • The 3x Downstream BCM in the Hall appears to be linear to ~2.5% relative to a luminosity monitor. We're currenly using this BCM for Charge Asymmetry Feedback
  • Recent measure of Charge Asymmetry Width is around 3000ppm. This appears to come from beam transmission through the Injector.
    • 100 keV region, upstream of an apertures, the width is ~100ppm.
    • After aperatures and chopper, in 5 MeV region, the width matches that in the Hall (~3000ppm)
    • To fix this, use of a corrector coil was used, but could not maintain steady beam for other halls. A better solution may be to tune the laser phase through the chopper. This may have an effect on the background measured by Compton.
  • The total transmission that MCC is able to measure does not appear to be a useful parameter for HAPPEX.
  • Because the writting of EPICS variables to the data stream has been disabled for most of SAGDH, a script needs to be written to find the average IA setpoint changes during a Charge Asymmetry Feedback run. Bryan will do this.

• Compton (David)

  • Recent tests have revealed a factor of 20 difference in background from beam current of 2 uA and 5 uA. This may be due to the chopper.
  • Currently commissioning the new Low Energy Photon detector.
  • Have moved the electron detector so that it is closer to the beam. Will use it when beam energy goes to 2 GeV.
  • There is some concern that coil pulsing may disturb the electron detector in it's new position

• Coil Pulsing(Kent)

  • To do coil pulsing, we will need the ability to turn off the accelerator Fast Feedback. Bryan and Kent are currently researching how to do this via EPICS Channel Access on the Counting House IOC.

• Laser Room(Brian)

  • Waiting for new Pockels Cells to arrive
  • Have been studying contributions of phase gradients and steering to position differences. Now starting to measure whether imaging suppresses steering effects.
  • Minor Setback: Detector was broken. Currently able to use the detector used by the g0 laser people.