Speaker
Marco Sertoli
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.103.pdf
Effects of the ICRH resonance position on the profile shape of the W
density in JET-ILW H-mode discharges
M. Sertoli1,2, F. J. Casson2, R. Bilato1, J. Flanagan2, J. Boom1, A. Shaw2, E. Delabie3 and
JET Contributors*
1
Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching, Germany
2
CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK
3
Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Ion cyclotron resonance heating (ICRH) with the power deposited close to the plasma
centre is necessary in JET-ILW to avoid tungsten (W) accumulation and its optimization
can lead to longer, more stable plasma operation. In this contribution, the effect of the
location of the ICRH resonance layer on the profile shape of the intrinsic W density has
been studied in JET-ILW H-mode discharge 85377. With a scan in toroidal magnetic field
from 2.5 to 2.85 (T) the resonance layer is moved from the high-field-side (HFS) to the
low-field-side (LFS), but still staying within the sawtooth inversion radius. While the main
plasma parameters show only slight changes and the sawtooth period remains unaffected,
moving the resonance layer towards the LFS leads to a 25% decrease in central W density
and in a reduction of the LFS asymmetry close to the resonance layer.
The experimental W density profile has been determined using the soft X-ray (SXR)
diagnostic and vacuum-ultra-violet (VUV) spectroscopy coupled together as explained in
[1]. This method has been recently upgraded to account for the strong poloidal asymmetries
typically present in the SXR emission profiles at JET. Contributions from low-Z impurity
and deuterium have been included using the visible Bremmstrahlung Zeff measurement [2]
with the assumption that their contributions are poloidally symmetric and that the only
other impurity contaminating the plasma (apart from W) is Be. The method has been found
to be robust for W concentrations above a few 10-5 and in cases where the contributions
from medium-Z impurities such as Ni is negligible.
The results are compared with modelling using the code NEO [3, 4] accounting for
centrifugal effects as well as temperature anisotropy of the ICRF heated H-minority ions
(modelled using TORIC-SSFPQL [5]).
[1] M. Sertoli et al 2015 Plasma Phys. Controlled Fusion 57, 075004.
[2] K.H. Behringer et al 1986 Nucl. Fusion 26, 751
[3] E. A. Belli et al 2008 Plasma Phys. Controlled Fusion 50, 095010.
[4] E.A. Belli et al 2012 Plasma Phys. Controlled Fusion 54, 015015.
[5] Brambilla M. et al 2009 Nucl. Fusion 49, 085004
* See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 10200”
