This target system provides a high-density
(
nuclei/cm
)
polarized He gas target for spin physics experiments.
The target employs the so-called spin-exchange technique.
In this technique He is polarized in a two-step process.
First, rubidium vapor is polarized by optical pumping with
circularly polarized 795 nm laser light. Second, the electronic polarization
of the Rb is transferred to the He nucleus in spin-exchange
collisions, in which He nuclei are polarized via the hyperfine interaction.
The target cell contains high pressure He gas and a small amount of
rubidium vapor. In addition, it
also contains a small amount of nitrogen to increase the
pumping efficiency.