  Fast rotation can improve the stability and confinement of fusion plasmas.
However, to maintain a rapidly rotating fusion plasma in steady state,
significant energy must be invested in spinning up each incoming fuel ion. We
show here that, under the right circumstances, collisional cross-field radial
fueling can directly transfer drift energy between outgoing and incoming ions
without the need for external power recirculation, thereby reducing the energy
costs of maintaining the rotation.
