Onset and saturation of ion heating by odd-parity rotating-magnetic-fields in a field-reversed configuration

TL;DR

This paper investigates how odd-parity rotating magnetic fields heat ions in a field-reversed configuration, revealing resonance conditions, thresholds for stochastic behavior, and the impact of magnetic geometry on heating efficiency.

Contribution

It identifies resonance conditions and the threshold for stochastic ion heating in FRCs, showing magnetic geometry reduces the heating threshold compared to tokamaks.

Findings

Maximum energy gain at specific resonances

Threshold for stochastic orbit transition explains heating onset and saturation

FRC geometry lowers heating threshold compared to tokamaks

Abstract

Heating of figure-8 ions by odd-parity rotating magnetic fields ($RMF_o$) applied to an elongated field-reversed configuration (FRC) is investigated. The largest energy gain occurs at resonances ($s \equiv \omega_R/ \omega$) of the $RMF_o$ frequency, $\omega_R$, with the figure-8 orbital frequency, $\omega$, and is proportional to $s^2$ for $s-even$ resonances and to $s$ for $s-odd$ resonances. The threshold for the transition from regular to stochastic orbits explains both the onset and saturation of heating. The FRC magnetic geometry lowers the threshold for heating below that in the tokamak by an order of magnitude.