Notes from Local Meeting Nov. 19, 2003

General Updates

• Hot checkout of Hall A is Nov. 26, 2003
• Lumi cans are installed in beamline
• Al Gavalya is making a drawing of the lumi installation for ops

Experimental Updates/Individual Updates

• Septum Heating

  • Pavel's Monte Carlo (MC) expects 50 W (@ 6 deg) of power deposited into each septum and Paul Brindza says we have 10 W cooling power
  • During our test, 25 W @9 deg/13x luminosity => 2W
  • No beam: 5.0 K; w/ beam: 5.2 K; => 2W = 0.2 K Estimate cooling power of 10 W/K
  • Because cooling power is dominated by thermal conductivity, there is a non-linear response between cooling power and temperature; say 50 W = 5 K but if the temp increases to 7.5 K, the cooling power increases from 10 W/K to 15 W/K
  • Shielding is required: Pavel's MC (center shielding) =>50 W ->18 W
    • Tungsten collimater parts have been ordered
    • Question of whether or not addition shielding is necessary outside of the transfer box (Doug, Kent)
  • With shielding the yoke temp will stay less than 9 K, but we don't know that the coil temp will be.
  • There won't be a collimator for the septum during Hypernuclear
  • Perhaps we should try to make the collimator removable to measure the difference in background.

• ⁴He Radiation Budget

  • 80% of lab budget, 5x as much as "usual" experiment
  • difficult to improve via shielding
  • we would like to measure the dose during week of running and extrapolate to 1 month

• Lumi Status

  • Detectors still need to be built
  • No more PMTs are needed and are good
  • Additional cabling necessary
  • PMTs require air or Nitrogen purge
  • Pedestal noise is still a large concern
  • Cables need to be terminated

• Source Status

  • Estimates of sizes of position differences:
    • Birefringence gradients of Pockels cells: using PITA slope of 30 ppm/V, estimate &Delta x < 285 nm
    • Lensing/Steering from PCs: &Delta x < 750 nm
    • Cathode gradients: &Delta x ~ 100 nm
    • IA cell coupling: &Delta x ~ 5 nm
  • Efforts to minimize position differences:
    • Adiabatic damping (decreases size of position differences by a factor <= 95
    • Imaging and insertable HWP will decrease effects from Pockels cell steering
    • Small PITA slope = 5 - 10 ppm/V
    • Feedback - corrector magnets for position and IA feedback
  • Characterization of waveplates - meausuring birefringence of other optics in beam path downstream of PC
  • Characterizing final PC (TX cell from Cleveland Crystals) - plans to order more?
  • New laser will be available soon (Dec) for testing => real optics system characterization, imaging development
  • G0 results:
    • Aanomalous results for out-of-phase x/y position difference RHWP scan
    • Huge possible position differences (> 20 &mu m ) related to larger beamspot

• Hachemi

  • Working on Compton upgrade - programming RPCs, port server, and working on cableing

• Ryan

  • Helping with the source
  • Working on saGDH analysis - getting pedestals for BCMs using Lumi

• Beam Line Status

  • (Musson) BCM electronics (10 kHz [new] and 1 kHz [old] will be tuned
  • BCms were sickly (maybe unusable?) during saGDH
  • BCM calibration would be useful for lumi tests, regression, dithering tests, etc.
  • New cavity electronics - January of February
  • Beam Modulation
    • Beam modulation magnets are working
    • New tool (to be implemented): bmw script will use EPICS word to turn FFB off before dithering

• Bryan

• Action items for Hall

  • Hachemi (w/ Bryan) - Lumi pedestal noise
  • Kent (w/ Ed) - ease of removal of the collimator for the septum
  • Hachemi (w/ Kent & Jack) - Lumi cabling and air/N2 purge
  • Kent - Cabling to extra BPM
  • Kent (w/ Musson) - new cavity cabling

• TEST PLANS for Dec-Feb run period

  • Hachemi: Beamline, recommission w/ Lumi installation
  • Kent: Septum heating
  • Hachemi: Lumi commissioning
  • Kent: BCM calibration
  • Kent: Dithering
  • Kent (or Lisa): Cavity BPM commissioning - lower priority because we need to wait for new electronics