Speaker
Joaquin Galdon-Quiroga
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1063.pdf
Acceleration of beam ions during edge localized modes
in the ASDEX Upgrade tokamak
J.Galdon-Quiroga1*, M.Garcia-Munoz1, K.G.McClements2, M.Nocente3, S.S.Denk4,
S.Freethy4, M. Hoelzl4, A.S. Jacobsen4, F.Orain4, J.F.Rivero-Rodriguez1, M.Salewski5,
L.Sanchis-Sanchez1, W.Suttrop4, D. van Vugt6, E.Viezzer1, M.Willensdorfer4, the ASDEX
Upgrade4 and EUROfusion MST1§ Teams
1
Dept. of Atomic, Molecular and Nuclear Physics, University of Seville, Seville, Spain
2
CCFE, Culham Science Centre, Abingdon OX14 3DB, United Kingdom
3
Dipartimento di Fisica ‘G Occhialini’, Università di Milano-Bicocca, Milano, Italy
4
Max Planck Institute for Plasma Physics, Garching, Germany
5
Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark
6
Eindhoven University of Technology, Eindhoven, The Netherlands
Acceleration of charged particles is ubiquitous in space, astrophysical and laboratory plasmas.
Magnetically confined fusion plasmas with in-situ measurements are an ideal testbed to
elucidate the physics underlying the different acceleration mechanisms. Experiments at the
ASDEX Upgrade tokamak provide, for the first time, evidence of beam ion acceleration during
edge localized modes (ELMs). Fast-ion loss detector (FILD) measurements show bursts of
enhanced fast-ion losses associated with individual ELM filaments [1]. Tomographic inversion
techniques applied to the FILD signal allow us to determine the velocity distribution of the lost
ions with unprecedented resolution in pitch angle and energy. A high-energy feature tens of
keV above the main neutral beam injection energy is observed, which shows multiple pitch
angle structures varying with the beam source and q95 values. These well-defined velocity space
structures suggest that the acceleration results from a resonant interaction between the beam
ions and parallel electric fields arising during ELM filament eruption, when magnetic
reconnection is believed to take place. Consistent with the FILD measurements, at the onset of
ELMs, bursts are often detected in electron cyclotron emission and also in soft X-ray channels
with lines of sight tangential to the plasma edge. Similar bursts reported in the MAST spherical
tokamak have been attributed to electron acceleration [2]. Full orbit fast ion simulations have
been carried out including the 3D perturbation fields of the ELM modelled with JOREK [3].
The filamentary-like pattern of the temporal evolution of fast-ion losses can be reproduced and
resonance structures associated with the energy gain of the ions are obtained. These findings
motivate the incorporation of a kinetic description of fast particles in ELM models, which may
shed light on the role of these fast particles in ELM stability as well as in the overall particle
and energy loss during the ELM cycle.
[1]M.Garcia-Munoz et al, Plasma Phys. Control. Fusion 55 124014 (2013)
[2]S.Freethy et al, Phys. Rev. Lett. 114 125004 (2015)
[3]G.T.A. Huysmans and O.Czarny, Nucl. Fusion 47 659 (2007)
§ H.Meyer et al, Nucl. Fusion 57 102014 (2017)
