Dynamic nuclear polarization of irradiated targets

We have irradiated and studied dynamic nuclear polarization in ammonia, deuterated ammonia, butanol, borane ammonia, methylamine, ethane and lithium borohydride in order to test these substances for potential use as polarized target materials. These studies were conducted using a polarized target system operating at a temperature of 1K and a magnetic field of 5T. The target system was set up in a beam line at the Stanford Linear Accelerator Center, enabling us to irradiate the targets in situ at 1K with a 6 to 20 GeV electron beam and to study their polarization properties simultaneously. Proton polarizations of ∼70% and deuteron polarizations of ∼25% were obtained in irradiated NH3 and ND3, with relatively short values of the polarizations growth time Tp. For both of these materials, the radiation resistance of the polarization was found to be approximately 30 times greater than for conventional chemically doped hydrocarbon targets. In the remaining irradiated materials tested, relatively small proton polarizations (∼30% or less) were obtained and these materials do not seem to be suitable for polarized target applications. Irradiated NH3 and ND3, however, are very promising as practical polarized target materials.