Notes from Local Meeting Nov. 19, 2003
In attendance: Bob Michaels, Lisa Kaufman, Tim Holmstrom, Ryan Snyder, Hachemi Benaoum, Bryan Moffit, and Kent Paschke.
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
Lisa Kaufman
Last modified: Mon Nov 24 11:37:44 EST 2003