Spectroscopic models for the characterization of energetic particle beams in tokamak edge plasmas

We examine the possibility for a diagnostic of energetic particle beams based on passive spectroscopy, with a focus on the atomic lines observed in the edge region of tokamaks. Our investigation employs a quasi-linear model for the collective electric field generated by the plasma-beam instability. If the beam is sufficiently energetic, the electric field can be comparable to the thermal Holtsmark microfield, and the corresponding Stark effect on atomic energy levels can be observable on spectra. We investigate this issue and perform new hydrogen line shape calculations. The applicability of the model to the diagnostics of runaway electrons is discussed. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)