Electron Cyclotron Heating in RFP plasmas

Abstract

Reversed field pinches (RFP) plasmas are typically overdense (ωpe>Ωce) and thus not suitable for conventional electron cyclotron (EC) heating and current drive. In recent high plasma current discharges (Ip>1.5 MA), however, the RFX‐mod device was operated in underdense conditions (ωpe<Ωce) for the first time in an RFP. Thus, it is now possible to envisage heating the RFP plasma core by conventional EC at the 2nd harmonic, in the ordinary or extraordinary mode. We present a preliminary study of EC‐heating feasibility in RFX‐mod with the use of beam‐tracing and full‐wave codes. Although not competitive—as a heating system—with multi‐MW Ohmic heating in an RFP, EC might be useful for perturbative transport studies, even at moderate power (hundreds of kW), and, more generally, for applications requiring localized power deposition.