Highlights
The polarized target
for CLAS, has been realized in collaboration between the INFN-Genova, the
University of Virginia, and Jefferson Lab. The target
operates in combination to a low-intensity electron beam and its system includes a superconducting
magnet to produce an highly uniform 5 T magnetic field and a 1K
liquid helium (LHe) refrigerator and a microwave
generator to polarize via DNP hydrogenated (NH3) or
deuterated (ND3) samples.
It is designed both to fit the
geometry CLAS and to allow the detection of multiparticle final states
for the study of single and double spin asymmetries in the exclusive channels. For this
purpose the magnet cryostat has a large opening window (+/- 55 degree) in
the forward direction as well as six lateral windows from 80 to
110 degree. The magnetic field is directed along the beam axis and the target can be
polarized parallel or antiparallel to it. The target insert is equipped with four
cells: ammonia and deuterated ammonia for the physics measurements, carbon to
check false asymmetries and to evaluate the nuclear background and one empty cell for beam
tuning . Different sensors are located on the insert: NMR coils for polarization
monitoring, thermometers, thermocouples and heaters
for the annealing process.
The target was succesfully operated for the first part of the EG1 running period from
September to December 98;
average polarization is 70 % for the proton and 20% for the deuteron.
Page written by Raffaella DeVita