Polarizing ³He by Spin Exchange with Potassium

Citation

Wang, Guodong (2004) Polarizing ³He by Spin Exchange with Potassium. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/69BR-5G30. https://resolver.caltech.edu/CaltechETD:etd-05202004-032505

Abstract

We present experimental studies on the spin-exchange optical pumping of ³He using alkali metal potassium vapor. High ³He polarizations are achieved using lower laser power than traditional rubidium-³He pumping studies. In addition, spin-exchange rate coefficient measurements for potassium-³He, rubidium-³He and cesium-³He pairs are reported.

By spin-exchange optical pumping with potassium vapor, a high ³He polarization has been achieved in a mid-sized double-chamber glass target cell using only 5 watts of Ti:sapphire laser power. The spin-exchange rate coefficients of potassium-³He, cesium-³He and rubidium-³He pairs are measured and compared. The results are k_SE = (4.0 ± 0.3) x 10⁻²⁰ cm³/sec for the potassium-³He pair, k_SE = (6.5 ± 0.4) x 10⁻²⁰ cm³/sec for the rubidium-³He pair and k_SE = (13.6 ± 1.3) x 10⁻²⁰ cm³/sec for the cesium-³He pair.

The results are consistent with theoretical predictions and confirm that the efficiency for spin-exchange polarization of ³He with potassium is significantly higher than with rubidium or cesium. The results motivate the development of high power diode lasers tuned to the appropriate potassium wavelengths. Applied to the production of polarized ³He as an atomic beam source for colliders, these developments could have significant impact on future studies of neutron spin structure. These studies may also have impact on magnetic resonance imaging using hyperpolarized ³He.

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