Speaker
Francisco Javier Artola
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I2.109.pdf
An in depth look into the physics of ELM triggering via vertical kicks
through non-linear MHD simulations
F.J. Artola1,2, G. Huijsmans3,4, M. Hoelzl5, P. Beyer1, A. Loarte2, Y. Gribov2 & JET Contributors*
1
Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille, France
2
ITER Organization, 13067 St Paul Lez Durance Cedex, France
3
CEA, IRFM, F-13108 St. Paul-lez-Durance Cedex, France
4
Eindhoven University of Technology, Eindhoven, The Netherlands
5
Max Planck Institute for plasma physics, Boltzmannstr. 2, 85748 Garching, Germany
Triggering of ELMs via vertical plasma position oscillations was first reported in the TCV
tokamak. These vertical oscillations often called "vertical kicks" were used for ELM frequency
control in the type-I ELM regime in ASDEX Upgrade and are routinely used for ELM control
at JET [1]. The conjectured mechanism destabilizing ELMs during the vertical motion was an
increase in the edge current pushing the pedestal to the peeling-ballooning unstable region.
In order to clarify the physics basis behind this ELM control approach and its potential for
application in ITER, we make use of the non-linear MHD code suite JOREK-STARWALL. We
have simulated for the first time the processes of vertical plasma movement and ELM
destabilization in an integrated and self-consistent form. Our simulations show that initially
stable plasmas are destabilized by the application of a vertical motion, where the unstable
modes present a peeling-ballooning structure in the linear phase. Plasmas with lower pedestal
currents require larger vertical displacements to trigger ELMs, which confirms the hypothesis
of the increased edge current as the ELM triggering mechanism. The origin of the current
induced during the vertical motion is also analysed, revealing that it arises from the
compression of the plasma cross section due to its motion through an up/down asymmetric
magnetic field. In the case of single null plasmas compression occurs when the plasma moves
vertically towards the X-point, with the velocity of the movement playing only a minor role.
The presentation will describe modelling of JOREK-STARWALL of ELM triggering with
vertical “kicks” for JET-C plasmas [1], comparing quantitatively code predictions with
experimental results, and its application to triggering of ELMs in ITER 7.5MA/2.65T plasmas.
[1] De la Luna, E., et al. "Understanding the physics of ELM pacing via vertical kicks in JET in view of
ITER." Nuclear Fusion 56.2 (2015): 026001.
*See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001″
