Beam-driven ion-cyclotron modes in the scrape-off layer of a field-reversed configuration

In the scrape-off-layer (SOL) of a field-reversed configuration, neutral beam injection can drive modes in the vicinity of the ion-cyclotron frequency. Depending on their properties, these modes can have differing macroscopic effects on the plasma. Using particle-in-cell simulations and semi-analytical methods, this work examines the properties of the various categories of ion-cyclotron modes that can be excited in the SOL environment, taking an ion beta of 10%. Propagation angle and beam injection angle are scanned from 0° to 90° with respect to the external magnetic field. The linear physics of these modes is treated foremost, but the non-linear physics, particularly regarding ion acceleration with consequences for plasma stability and fusion reactivity, is also examined. Near perpendicular propagation and beam injection are found to give the greatest fusion enhancement. This result derives from an extension of wakefield acceleration physics to the case of ion acceleration in a magnetized fusion plasma. The non-linear physics of this regime is thus given particular attention.