The polarized cryogenic H/D target
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Highlights

FullTargetPhoto.jpg (97582 bytes)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.


target.gif (79905 bytes) 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