EPJ Web Conf.
Volume 157, 201722 Topical Conference on Radio-Frequency Power in Plasmas
|Number of page(s)||5|
|Published online||23 October 2017|
RF Sheath-Enhanced Plasma Surface Interaction Studies using Beryllium Optical Emission Spectroscopy in JET ITER-Like Wall
a Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6169, USA
b IRFM CEA Cadarache 13108 Saint Paul lez Durance France
c LPP-ERM/KMS, Royal Military Academy, 30 Avenue de la Renaissance B-1000, Brussels, Belgium
d Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany
e CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, UK
* Corresponding author: email@example.com
Published online: 23 October 2017
A dedicated study on JET-ILW, deploying two types of ICRH antennas and spectroscopic observation spots at two outboard, beryllium limiters, has provided insight on long-range (up to 6m) RFenhanced plasma-surface interactions (RF-PSI) due to near-antenna electric fields. To aid in the interpretation of optical emission measurements of these effects, the antenna near-fields are computed using the TOPICA code, specifically run for the ITER-like antenna (ILA); similar modelling already existed for the standard JET antennas (A2). In the experiment, both antennas were operated in current drive mode, as RF-PSI tends to be higher in this phasing and at similar power (∼0.5 MW). When sweeping the edge magnetic field pitch angle, peaked RF-PSI effects, in the form of 2-4 fold increase in the local Be source,are consistently measured with the observation spots magnetically connect to regions of TOPICAL-calculated high near-fields, particularly at the near-antenna limiters. It is also found that similar RF-PSI effects are produced by the two types of antenna on similarly distant limiters. Although this mapping of calculated near-fields to enhanced RF-PSI gives only qualitative interpretion of the data, the present dataset is expected to provide a sound experimental basis for emerging RF sheath simulation model validation.
© The authors, published by EDP Sciences, 2017
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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