Experimental demonstration of synergy between electron cyclotron and lower hybrid current drive on Tore Supra
Non-inductive current drive (CD) has two main applications in tokamaks: sustainment of a substantial fraction of the toroidal plasma current necessary for the plasma confinement and control of the plasma stability and transport properties by appropriate shaping of the current density profile. For the first kind of applications, lower hybrid (LH) waves are known to provide the highest efficiency, although with limited control capability. Conversely, electron cyclotron (EC) waves drive highly localized currents, and are therefore particularly suited for control purposes, but their CD efficiency is much lower than that of LH waves. LH waves can efficiently interact with electrons with substantially higher parallel velocities, poorly collisional and insensitive to trapping, thus carrying a larger current than the slower electrons interacting with the EC waves. For these reasons, the idea of combining the two CD systems has been proposed and investigated since the early �80s theoretically and experimentally. Moreover, various calculations have demonstrated an interesting property: the current driven by the simultaneous use of the two waves, ILH+EC, can be significantly larger than the sum ILH+IEC of the currents separately driven by the two waves in the same plasma conditions. This property, hereafter called synergy effect. Early experiments tried to demonstrate this effect, but were inconclusive. Effective coupling of up-shifted and down-shifted EC waves with the LH driven electron tail has been observed in FTU in a qualitative way, due to the lower effects on current at the higher densities involved. Therefore, so far a well-documented qualitative and quantitative experimental demonstration of the synergy effect in steady state was missing. Here, the first experimental demonstration of this type is reported.
Bibliographic Reference: An oral paper given at: 31st EPS Conference on Controlled Fusion and Plasma Physics Organised by: CCLRC Rutherford Appleton Laboratory (GB); EURATOM/UKAEA Fusion Association (GB); Imperial College London Held at: Imperial College London (
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: firstname.lastname@example.org
Record Number: 200417623 / Last updated on: 2004-07-13
Original language: en
Available languages: en