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Abstract

Active current drive with lower hybrid (LH) waves in the advanced scenario plasmas at JET-EFDA was successful after a systematic study of the coupling problems that derive from the H-mode features of the edge plasma, namely very low density and ELM activity. The LH coupling has been improved compared to the past, by making the edge plasma in front of the LH launcher denser and more uniform. Injecting deuterated methane (CD (4)) from a nearby gas pipe increases the density in front of the LH launcher at least by a factor of 1.5, above the cut-off value for the LH frequency. A better matching of the plasma shape to that of the LH antenna makes the plasma ahead of the LH launcher more regular along the poloidal angle. These two techniques together have permitted a balanced supply of the three LH grills, with an average reflection below 4%, as in the previous L-mode operation. CD (4) does not affect the performances nor does it contaminate the main plasma up to the maximum flow rate so far used, theta CD (4) > 10 {22} el s{-1} and now it is routinely applied in JET (up to 4MW have been injected for longer than 8 s) with very encouraging results for LHCD. Even though CD (4) is not suitable for ITER for tritium retention, the possibility of controlling locally and safely the scrape-off plasma density has been demonstrated.

Additional information

Authors: PERICOLI RIDOLFINI V, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);PODDA S, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);TUCCILLO A A, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);ERENTS S K, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);MAILLOUX J, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB);EKEDAHL A, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);SARAZIN Y, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Plasma Physics and Controlled Fusion 46 (2004), pp. 349�368
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://stacks.iop.org/PPCF/46/349
Record Number: 200417356 / Last updated on: 2004-01-27
Category: PUBLICATION
Original language: en
Available languages: en
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