Speaker
Tomas Markovic
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O3.108.pdf
High-field side error field effects on H-mode plasma performance and
their correction in ITER-like experiments on COMPASS
T. Markovic1,2, M. Peterka1,2, A. Loarte3, J. K. Park4, Y. Gribov3, J. Havlicek1, R. Panek1,
P. Hacek1,2, M. Hron1, M. Imrisek1,2, K. Kovarik1, L. Kripner1,2, K. Mitosinkova1,2, M. Sos1,
M. Tomes1,2, J. Varju1, P. Vondracek1,2, V. Weinzettl1 and the COMPASS team1
1
Institute of Plasma Physics of the CAS, Prague, Czech Republic
2
Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic
3
ITER Organization, 13067 St Paul-lez-Durance, France
4
Princeton Plasma Physics Laboratory, Princeton University, Princeton, USA
Plasma performance in magnetic confinement fusion (MCF) devices is degraded by the
presence of error fields (EF) e.g. due to misalignments of magnetic coils during assembly
process. By utilizing error field correction (EFC) coils, detrimental effects of EF can be
annulled or, alternatively, artificially induced. Typically, EFC coil-induced EF couples
equally well to both the core and the edge plasma resonant surfaces due to their location on
the low-field side (LFS) of the device. However, coupling of the intrinsic EF originating at
the high-field side (HFS) of a tokamak (e.g. due to a tilt of the toroidal field coils (TF) or of
the central solenoid (CS)) is different. The effects of such EF on the plasma or the need for
their correction have not been sufficiently characterized yet (mainly due to lack of
capabilities of the present MCF devices to generate controlled HFS EF). However, they are
highly important for ITER since the magnitude and correction of such effects have direct
implications on the accuracy of installation and alignment of the TF/CS coil sets.
In the COMPASS tokamak we have used EFC coils at the HFS to generate controlled EF in
ITER-like (q95=3) plasmas, mimicking the effects of tilt and displacement of the CS on
H-mode plasma confinement and on the L-H transition/H-mode access. We report that these
effects prevent H-mode access (due to disruptions), and if EF are applied to a pre-existing
H-mode, they lower the energy confinement by 20%. We show that while n=1 EFC by LFS
coils can fully recover the H-mode energy confinement, H-mode accessibility is only
partially restored – 50% of the discharges in which this EF correction scheme is applied
disrupt. Initial experiments show that an addition of the top and bottom coils (as available in
ITER) to the correction of the HFS EF decreases significantly this disruption rate. The
experimental observations are interpreted using IPEC and MARS-F modelling and the
implications for ITER are discussed.
