Effects of Radial Electric Fields on Alpha Particle Confinement in the CAT-1 Levitated Dipole Device

Radial electric fields are known to arise from non-ambipolar transport in dipole-confined plasmas, yet their effects on high-energy alpha particle confinement remain systematically unexplored for compact levitated devices. This study employs test-particle simulations based on the parameters of the China Astro-Torus 1 (CAT-1) levitated dipole experiment to investigate how such fields influence alpha particle trajectories, losses, and slowing-down confinement. The key result is that a moderate radial electric field can increase the confined fraction of alphas by up to 40% within the ion slowing-down time, a substantial improvement for heating the background plasma. Furthermore, the confinement fraction varies systematically with the strength of the inner field ( E in ) and the ratio of outer-to-inner field ( κ), with high E in and κ > 1 yielding optimal results. These findings suggest that tailoring the radial electric field profile offers a novel, knob-like handle for controlling alpha particle heating in dipole fusion concepts.