Community Research and Development Information Service - CORDIS

Abstract

X- and O-mode high field side launch are compared for ECH breakdown and startup of tokamak plasmas. X-mode power is not absorbed at the cyclotron resonance but uniquely at the upper hybrid resonance, displaced to the low field side of the cyclotron resonance. O-mode power, however, is absorbed at the cyclotron resonance as well. The displacement of the upper hybrid resonance to the low field side with O-mode launch is significantly smaller than with X-mode launch due to the lower densities produced at the same microwave power level. The result is a more central and less localised breakdown with O-mode launch. The breakdown characteristics of X- and O-mode launch are seen to affect the position of the initial plasma current centroid in the poloidal cross section. A strong correlation is observed between the initial current ramp rate and the initial plasma current position, which is probably due to the dependence of the plasma inductance, toroidal electric field, and field-line connection lengths on the plasma major radius. O-mode launch starts the plasma more centrally than X-mode launch and results in higher current ramp rates. X-mode startup occurs further to the low field side where current ramp rates are observed to be poor.

Additional information

Authors: WHALEY D R ET AL., Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Lausanne (CH);CARDINALI A, ENEA, Centro Ricerche Energia Frascati, Roma (IT)
Bibliographic Reference: Report: LRP 449/92 EN (1992)
Availability: Available from Confédération Suisse, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, 21 avenue des Bains, 1007 Lausanne (CH)
Record Number: 199210402 / Last updated on: 1994-12-02
Category: PUBLICATION
Original language: en
Available languages: en
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top