Speaker
Laurent Colas
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.101.pdf
2D mappings of ICRF-induced SOL density modifications on JET
L. Colas1, P. Jacquet2, V. Bobkov3, M. Brix2, L. Meneses4, K. Kirov2, E. Lerche2,5, C.C.
Klepper6, M. Goniche1, A. Křivská5, P. Dumortier2,5, A. Czarnecka7 and JET contributors*
EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK
1
CEA, IRFM, F-13108 Saint Paul Lez Durance, France.
2
CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK.
3
Max-Planck-Institut für Plasmaphysik, Garching, Germany.
4
Instituto de Plasmas e Fusão Nuclear, IST, Universidade de Lisboa, Lisboa, Portugal.
5
LPP-ERM-KMS, TEC partner, Brussels, Belgium.
6
Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, USA.
7
IPPLM, Hery 23 Str., 01-497 Warsaw, Poland.
Localized Scrape-Off Layer (SOL) modifications have for long been evidenced on open
magnetic field lines near active Ion Cyclotron (IC) wave launchers. These changes were
shown to influence the reflection coefficient of Lower Hybrid grills, the first wall sputtering
and heat loads. However, resolving their complex 3D spatial structure remains challenging.
This contribution investigates SOL density distributions, measured on JET by Lithium
beam emission spectroscopy and X-mode reflectometry. Assuming a parallel homogeneity
of the IC-induced SOL patterns, the ratio of density with or without IC waves was plotted
versus the location of observation points along the diagnostic lines of sight, mapped in front
of each IC antenna. This technique was applied to L-mode pulses where the JET A2 and
ITER-like antennas were toggled over a scan of the edge safety factor. 2D (radial/poloidal)
maps were thus produced for each diagnostic/antenna pair, for current-drive strap phasing.
The IC-induced relative density changes, reproducible from pulse to pulse, are most
pronounced when the diagnostics magnetically connect in front of active IC launcher
mouths. They are radially localized near antenna side limiters and extend a few cm in front of
them, remaining 2-3cm outside the separatrix. They are poloidally inhomogeneous: density
depletion is generally observed, but the density also increased locally above one A2 antenna.
Reproducing the parallel extent, the radial width and poloidal asymmetry of the observed
SOL patterns puts constraints on RF-sheath modelling. Assuming that IC-specific sputtering
occurs on wall elements connecting to the flux tubes with modified density, the maps outline
possible locations for IC-induced W sources that could not yet be evidenced directly on JET.
*
See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001″
