Electron burst driven by near electric field effects of lower-hybrid launchers

Laurent Valade (1) , Annika Ekedahl (1) , Philippe Ghendrih (1) , Yanick Sarazin (1) , Yuuichi Asahi (1) , Hugo Bufferand (1) , Elisabetta Caschera (1) , Pierfrancesco Di Cintio (2) , Guido Ciraolo (1) , Guilhem Dif-Pradalier (1) , Peter Donnel (1) , Xavier Garbet (1) , Pierre-Antoine Giorgi (1, 3) , Virginie Grandgirard (1) , Guillaume Latu (1) , Stefano Lepri (4) , Roberto Livi (5) , A. Nouri (3) , Eric Serre (6)

1 IRFM - Institut de Recherche sur la Fusion par confinement Magnétique
2 ISC - Istituto dei Sistemi Complessi [Firenze]
3 L2M - Laboratoire de Microstructures et de Microélectronique
4 CNR - National Research Council of Italy | Consiglio Nazionale delle Ricerche
5 UniFI - Università degli Studi di Firenze = University of Florence = Université de Florence
6 M2P2 - Laboratoire de Mécanique, Modélisation et Procédés Propres

Hotspot generation by lower-hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D-1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function. An island structure is formed in the suprathermal part at the phase velocity of the external electrostatic drive. The non-linear features enhance the plasma response, driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function, with extent reaching one thermal velocity, is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of the small-scale features generated by the LH launchers, which are responsible for the interaction with the cold electrons. This mechanism can trigger hotspot generation further in the scrape-off layer than otherwise expected.

Mots clés: hot electron plateau; hotspot generation; island overlap; kinetic; lower hybrid; resonance; scrape-off layer; heat-flux; waves

Domaines: Génie des procédés

Laurent Valade, Annika Ekedahl, Philippe Ghendrih, Yanick Sarazin, Yuuichi Asahi, et al.. Electron burst driven by near electric field effects of lower-hybrid launchers. Contributions to Plasma Physics, 2018, 58 (6-8), pp.465-470. ⟨10.1002/ctpp.201700156⟩. ⟨hal-02116142⟩