Status of Frozen‐spin Polarized HD Targets for Spin Experiments

The first experiments have been carried out with polarized HD targets at the Laser‐Electron‐Gamma‐Source (LEGS) facility. By holding targets at low temperature and high field (17 mK and 15 Tesla) in a Dilution Refrigerator (DF) for six weeks a frozen‐spin state was reached, with equilibrium polarizations for protons and deuterons of 70% and 17%, respectively. Multiple measurements of the relaxation times and multiple transfers of the targets reduced these values so that experimental runs were carried out with polarizations of 30% and 6%, respectively. The relaxation times for protons and deuterons were observed to be 13 days and 36 days, respectively, in the beam line cryostat at 1.3 K and 0.7 Tesla magnetic field. For the future runs significantly higher D polarizations are possible by transfer of spin from the proton to the deuteron using an rf forbidden adiabatic fast passage. Higher polarizations and longer relaxation times are expected from ongoing development.