Minutes - Old Minutes

To Do

• Are we OK with natural calcium (regular target ladder, reduce Ca cell size)?
  • Yes: A_nat = 40.1068, instead of 8/20= 40% neutron excess, we go to 7.892/20.1076=39.3% neutron excess [both diluted by ~10% for 90% purity of 48Ca target].
  • Note, Lithium and natural Calcium can just be put in the regular slots and replaced if scattering chamber vacuum is lots (need spares and will need to measure relative thicknesses, but doable).

• Are we OK with racetrack cells? OK with 10cm for all cryotargets?
  • Dave Gaskell will check with Kent Paschke about HAPPEX performance
  • Only issue with 10cm cells is acceptance at large angle. EMC limited to 35 degrees, x>1 is <15 degrees for very large x, larger angles for x~1, but normalization is less of an issue.
  • For x>1 high Q^2, this will mean a theta-dependent acceptance which could translate into a Q^2 dependence at fixed x. How much of an issue is this?

• What do we need for optics targets and dummy targets?
  • Currently have multiple optics and dummy options.
  • Can have single optics and single dummy instead, gain a couple extra spaces for solid targets (this is the 13 foil target scenario)

• Check single-ladder vs. double-ladder scenarios. What do we need, what can we live with?
  • Single ladder #1: 2 cryotargets + 48/40Ca cell + optics foil (1) + dummy (1) + 13 solid targets
  • Single ladder #2: 2 cryotargets + 48Ca cell + optics(1) + dummy(1) + 17 solid targets (1 is 40Ca)
  • Double ladder #1: 2 cryotargets, 1 ladder with 48/40Ca + multiple optics/dummy + ~11 targets, one ladder with ~17 solid targets. Note that dummy/optics will be same for both, may want 1 or 2 duplicate foils.

• For SRC data (8-12 degrees), how large does the 48Ca cell have to be able to separate the target windows from 48Ca? If this isn't feasible, we'll need to do a dummy subtraction (which presumably means that the 40Ca has to stay in the same cell to avoid even worse systematics).

• What beam current do we need for 3He/4He? Cooled by 4K coolant, which will limit power deposition, probably limiting beam current below 80uA for 10cm cells.
  • Answer: Want to run with as much current as cooling system can handle (3He at x>2 is critical data and will take significantly more time than other targets with the large dummy subtraction)
  • Dave Meekins will calculate current limit based on cooling power

• Very crude notes from the call copied below:

Homework: Scenario 1: Cryo + Calcium + 13 [minimum optics sled and dummy]. Tweaked: natural calcium + ~18 targets Scenario 2: 2 target ladders.

[is natural calcium OK?] [then can make it smaller], take out of cell and maybe 5 more solid targets.

Questions about details of target ladder: Optics target(s)? Dummy target(s)? Cryo targets? - 4cm or 10cm? [cells with 4 and 10cm versions have worse performance]

Answers: 10cm OK for everything [low boiling]

Give up spare loop (3 --> 2 cryotargets) Allows 20 solid targets (if smaller than usual) 13 solid target with Ca cell [right now, 2-3 solid targets for multiple optics/dummy]. With single set of carbon foils and single dummy, can do 13solid targets. Don't forget; carbon, optics, dummy have to be on both ladders

[Lithium doesn't require 'cells' - put it in and replace if lose vacuum. store in mineral oil, pumping+beam remove it]'

Angle range? 8-50 degrees [key angles, 8-10, 20, 35] **Calcium target: have to figure out where windows cause issues. At small angle (8-10 degrees) have trouble separating cell windows from target. Longer window help? or rely on dummy?

11 GeV at 80uA (in general). How much luminosity for 3He and 4He. He targets use 4k refrigerant; larger cell (because higher pressure). 10cells - 3" diameter --> (1.5" + aluminum) for electron on the way out. Can't do high pressure without thicker wall.

Racetrack cells (as with Hall A), thinner walls (maybe), less material going out. 2cm wide. [20cm cells had poor performance, 10cm worked better]. Used for HAPPEX, see how they worked.

4k refrigerant --> need to know beam current for target cooling. [has to go and calculate what's possible].

4 cryotargets. 1 'special' cell - 40/48Ca. All other targets do NOT require special cells [e.g. no waterfall, no 40Ar]

NOTE: with cigar cells, we do NOT need to pull out target ladder to switch H/D with 3He/4He - that can be done remotely [8 hours]. Go into chamber and swap ladders [2 days + cooldown time]. Maybe save time if overlap with maintenance day (but requires regular buisness hours).

May 30, 2013

• Organization and coordination
• Discussion Slides

To Do

• 2016 (aka Boron) running:
  • EMC - look into 20 vs 30 degree running, think about sneaking 9Be in. --> John/Dave/Aji
  • SRC - make sure 17degrees doesn't really work. Do time estimate for 12 degrees --> Nadia/John

• 2017/8 (final running)
  • Targets - Take list of potential new targets (which have some motivations jotted down) and add rest of them to make sure they have valid physics motivations as well. Check for alternate borons. Check Tin and Silver for feasibility/maximum currents. Make more strawberry jam for bribes. Maybe peach. --> Nadia/John
  • Thickness measurements - investigate other methods for doing thickness measurements (attenuation,...?) --> Dave (I think he volunteered, if not, I'm sure someone else will)