Sunday, May 19, 2013

1305.3295 (Joshua Pierce et al.)

Dynamically polarized target for the g2p and GEp experiments at
Jefferson Lab

Joshua Pierce, James Maxwell, Toby Badman, James Brock, Christopher Carlin, Donald Crabb, Donal Day, Nicholas Kvaltine, David Meekins, Jonathan Mulholland, Joshua Shields, Karl Slifer, Christopher Keith
We describe a dynamically polarized target that has been utilized for two electron scattering experiments in Hall A at Jefferson Lab. The primary components of the target are a new, high cooling power 4He evaporation refrigerator, and a re-purposed, superconducting split-coil magnet. It has been used to polarize protons in irradiated NH3 at a temperature of 1 K and at fields of 2.5 and 5.0 Tesla. The performance of the target material in the electron beam under these conditions will be discussed. Maximum polarizations of 55% and 95% were obtained at those fields, respectively. To satisfy the requirements of both experiments, the magnet had to be routinely rotated between angles of 0, 6, and 90 degrees with respect to the incident electron beam. This was accomplished using a new rotating vacuum seal which permits rotations to be performed in only a few minutes.
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