Energy Spectrum of Lost Alpha Particles in Centrifugal Mirror Confinement

Due to their good stability and differential confinement features, centrifugal magnetic mirrors have experienced a recent resurgence as a basis for magnetic fusion energy designs. Alpha particles produced in fusion reactions carry anywhere from 20% to 100% of the fusion power, depending on the reaction, and are typically born at temperatures much higher than the confining centrifugal potential, raising the possibility of immediate loss. Knowing their outgoing energy spectrum may be helpful for optimizing direct conversion schemes and is vital to understanding the power balance of the reactor. We derive analytical expressions for the energy spectrum and confinement times of lost alpha particles in centrifugal mirror fusion reactors, and validate them via Monte-Carlo simulations. Although we focus on alpha particles in a centrifugal potential, our results hold for any fast ion species subject to any applied potential, providing a wide range of applicability to present day mirror devices.