Polarized Ion Sources and Targets

Nuclear forces are known to depend on the spin angular momentum of the interacting nucleons, so control of their angular momentum is essential if this dependence is to be studied in nuclear scattering or reaction experiments. Creation of a non-equilibrium distribution of spins means that the nuclear system becomes polarized, with one or more spin angular momentum states enhanced in population compared to the rest.

The production and use of nuclear spin polarized beams and targets have for many years been among our group’s principal research thrusts. Polarized beams of H^± or D^± ions are produced at the Triangle Universities Nuclear Laboratory (TUNL) by an Atomic Beam Polarized Ion Source which was designed, constructed, and commissioned during 25 person-years of effort by TUNL faculty, staff, and graduate or undergraduate students. Since it was initially installed on an accelerator at TUNL in 1989, beams from this ion source have been used for experiments each year during more than half of the calendar days. The source has also been enhanced by the addition of a Spin-Filter Polarimeter which allows users to monitor the beam polarization continually during actual experiments.

Recent experimental need has also emerged at TUNL for polarized ³He targets. Work is underway in our group to construct systems which will provide, via spin-exchange with optically pumped rubidium vapor, a gaseous polarized ³He target at pressures of 0.3 to 1 bar. This target will initially be used for charged particle scattering experiments of spin-correlation parameters. These systems are being designed in close collaboration with scientists at the nearby laboratories of Amersham Health in the Research Triangle Park, who are developing similar systems for enhanced medical imaging purposes.