SPIN-POLARIZING HE-3 NUCLEI WITH AN ARC-LAMP-PUMPED NEODYMIUM-DOPED LANTHANUM MAGNESIUM HEXALUMINATE LASER

We report a systematic study of optical pumping of He-3 nuclei by metastability exchange using an arc-lamp-pumped neodymium-doped lanthanum magnesium hexaluminate (Nd:LMA) laser. The laser produces 6 W at 1083 nm in a 1.5-GHz bandwidth and yields a substantial improvement in attainable nuclear polarization and pumping rates. Spin-polarized He-3 has applications in several fields of physics; the focus in this article is on targets for nuclear physics, which require high pumping rates to maintain the highest polarization. We have studied the influence of the He-3 pressure, pumping transition, discharge intensity and frequency, cell size and shape, and laser power on both the polarization and pumping rate. Under ideal conditions, we obtain 85% nuclear polarization. With pumping rates of 10(18) (10(19)) atoms/s, 82% (50%) polarization is obtained. We have found a pressure-dependent saturation of the increase in pumping rate with laser power. Based on our results, we discuss projections for the performance of both internal and external targets.