Speaker
Description
Electromagnetic modes are routinely observed in tokamaks during runaway electron (RE) experiments [1-3]. These modes lie in both the Alfvénic and the lower hybrid frequency ranges. Theory and recent experiments suggest that such modes can enhance the pitch-angle scattering of REs [4], help reduce their maximum energy [5] and enhance their radial transport.
These modes therefore play a dual role: they provide a diagnostic tool for the underlying RE distribution function while also offering a means of RE attenuation. The latter can be achieved either via passive self-generation of the waves or via their active external excitation.
This contribution aims at characterizing these modes by introducing a new simulation framework for tokamak RE plasmas, coupling the Fokker-Planck code LUKE [6] with the linear plasma wave solver ALPS [7] – the latter originally developed for astrophysical plasmas and here applied to tokamak parameters for the first time. RE distribution functions are generated by LUKE and passed as input to ALPS, which computes the resulting waves for arbitrary distributions. This LUKE-ALPS framework is then benchmarked against experimental TCV observations, using high frequency electromagnetic wave diagnostics (ICE, LHPI) and hard X-ray diagnostics (BGO, LABrDoRE).
Preliminary results and the current status of this benchmarking effort will be presented, with the aim of establishing a consistent picture connecting the wave signature measured by ICE and LHPI with the hard X-ray spectra measured by LaBrDoRE.
[1] DA Spong, et al. Physical Review Letters, 120(15):155002, 2018.
[2] WW Heidbrink, et al. Plasma Physics and Controlled Fusion, 61(1):014007, 2019.
[3] W Bin, et al. Physical Review Letters, 129(4):045002, 2022.
[4] Tünde Fülöp, et al. Physics of Plasmas, 13(6), 2006.
[5] H Choudhury, et al. Physical Review Letters, 136(2):025101, 2026.
[6] J Decker, et al. Euratom-CEA Report No. EUR-CEA-FC-1736, 2004.
[7] Daniel Verscharen, et al. Journal of Plasma Physics, 84(4):905840403, 2018.