Solid Target PVDIS
From Hall A Wiki
minutes of meeting on 01/18/2013
attendee: JP Chen, Paul Souder, David Meekins,Christopher D. Keith,Josh Pierce, Whit Seay, Robin Wines, Paul E. Reimer,Seamus Riordan,Thia Keppel, Zhiwen Zhao
- 1. The PVDIS target will be similar to G0 target, but twice as long. The boiling effect will be larger, but the density fluctuation requirement is moderate. Larger pump and higher repetition rate will help.
- 2. PVDIS acceptance requires 35 degree polar angle with 40cm long target. This limits the vertical distance between targets need to be at least 11" and the total about 30" is needed to accommodate cryo,dummy and optic targets arranged vertically. Currently the solenoid upstream entrance opening is 26" in design and limited by SIDIS requirement., we need to check if larger opening is allowed. Another possible solution is to have cryo target move vertically and solid target move horizontally to form a more compact system.
- 3. There is limited space between target and first plane of baffle, It's currently 5.5cm in design, but can be changed slightly. So it's difficult to put vacuum window in between. One solution is to have the target vacuum chamber enclose the first plane of baffle. This implies that the vacuum chamber will be a part of the alignment task. (baffle planes are now 9cm thick lead with distance between planes about 20cm, neutron shielding may take additional space though. It should have enough space for the window.)
- 4. Polarization from LH2 is 0.1ppm and 8ppm from LD2 in the 1.5T solenoid field at 20k, while PVDIS asymmetry is a few hundred ppm. To have better than 1% measurement, we need to depolarize LD2. The T1 of LD2 is long (see note below) and it can be depolarized with polarization measured outside of the solenoid field.
note from Chris about T1 of LD2 reference to T1 in liquid D2 at 20.3 K and 1.2 tesla: R Wang and D White, Rev Sci. Instr. 42, 887 (1971) T1 depends on the para/ortho concentration, and is very different for the two orbital states. At concentrations near the equilibrium value (~2% para), one finds T1(para) ~ 1/2 sec T1(ortho) > 1 hour