Abstract

Use of new 3-strap ICRF antennas with all-tungsten (W) limiters in ASDEX Upgrade results in a reduction of the W sources at the antenna limiters and of the W content in the confined plasma by at least a factor of 2 compared to the W-limiter 2-strap antennas used in the past. The reduction is observed with a broad range of plasma shapes. In multiple locations of antenna frame, the limiter W source has a minimum when RF image currents are decreased by cancellation of the RF current contributions of the central and the outer straps. In JET with ITER-like wall, ITER-like antenna produces about 20% less of main chamber radiation and of W content compared to the old A2 antennas. However the effect of the A2 antennas on W content is scattered depending on which antennas are powered. Experiments in JET with trace nitrogen (N2) injection show that a presence of active ICRF antenna close to the midplane injection valve has little effect on the core N content, both in dipole and in -90° phasing. This indicates that the effect of ICRF on impurity transport across the scape-off-layer is small in JET compared to the dominant effect on impurity sources leading to increased impurity levels during ICRF operation.

Original languageEnglish
Pages (from-to)1194-1198
Number of pages5
JournalNuclear Materials and Energy
Volume12
DOIs
StatePublished - Aug 2017
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2016 The Authors

Keywords

  • 3-strap
  • A2 antenna
  • ASDEX Upgrade
  • ICRF
  • ILA
  • ILW
  • JET
  • RF sheath
  • Sputtering
  • Three-strap

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