The interaction of spin-polarized particles in plasmas has developed from a largely theoretical topic into an emerging experimental field with potential applications ranging from novel polarized particle sources to nuclear fusion. A central question is whether an initially prepared spin polarization can survive the extremely strong and rapidly varying electromagnetic fields encountered in laser-produced plasmas.
Over the past years, our group and collaborators have developed the theoretical framework for describing spin dynamics in plasma-based accelerators, including the implementation of spin precession in particle-in-cell simulations. These studies indicate that high degrees of polarization can be preserved during laser-plasma acceleration and have led to concepts for generating energetic polarized proton and electron beams.
In this talk, I will review the underlying spin dynamics and the mechanisms that can lead to polarization loss, and discuss strategies for producing and accelerating polarized electrons and ions. Particular emphasis will be placed on our recent experiments at the PHELIX laser at GSI, where we demonstrated for the first time that the nuclear polarization of pre-polarized ^3He is preserved during laser-driven acceleration to MeV energies. This result provides experimental support for the concept of using pre-polarized targets in high-intensity laser-plasma experiments.
Finally, I will discuss the prospects for polarized fusion. While the PHELIX experiments demonstrate that nuclear polarization can survive the extreme conditions of a laser-produced plasma, a major challenge for future fusion experiments is the production and delivery of sufficiently large quantities of highly polarized fuel. Possible pathways toward overcoming this limitation and realizing experiments with polarized fusion fuel will be presented.
Stephan Kuschel