Nuclear hyperpolarization of 3He by magnetized plasmas

TL;DR

This paper presents a novel method to hyperpolarize 3He nuclei at high magnetic fields using a magnetized plasma, achieving significant polarization levels without laser techniques, with potential applications in high-precision magnetometry.

Contribution

It introduces a new plasma-based hyperpolarization technique for 3He at high magnetic fields, expanding options beyond laser-based methods.

Findings

Achieved 1-9% nuclear polarization in 3He using magnetized plasma.

Demonstrated application of hyperpolarized 3He in high-precision magnetometry.

Identified the alignment-to-orientation conversion mechanism as key to polarization.

Abstract

We describe a method to hyperpolarize 3He nuclear spins at high magnetic fields (4.7 Tesla) solely by a magnetized plasma. The conditions for such a magnetized plasma are fulfilled when the mean free path of the free electrons is much larger than their gyration radius in the rf gas discharge. Investigations are carried out in the 1-15 mbar pressure range with rf excitation at ~100 MHz. Quantitative NMR measurements show that for different cell sizes and 3He densities nuclear polarizations in the range 1% to 9% are observed. We explain this phenomenon by an alignment-to-orientation conversion mechanism in the excited 2 3P state of 3He which is most efficient when the Zeeman and the spin-orbit energies are comparable. The method appears as a very attractive alternative to established laser polarization techniques (spin exchange or metastability exchange optical pumping). Application to 3He nuclear magnetometry with a relative precision of 10-12 is demonstrated.