A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks

A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks

A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks 150 150 Mathew

A survey of electron Bernstein wave heating and current drive potential for spherical tokamaks

The electron Bernstein wave (EBW) is typically the only wave in the electron cyclotron (EC) range that can be applied in spherical tokamaks for heating and current drive (H&CD). Spherical tokamaks (STs), which feature relatively high neutron flux and good economy, operate generally in high-ß regimes, in which the usual EC O- and X- modes are cut-off. In this case, EBWs seem to be the only option that can provide features similar to the EC waves-controllable localized H&CD that can be utilized for core plasma heating as well as for accurate plasma stabilization. The EBW is a quasi-electrostatic wave that can be excited by mode conversion from a suitably launched O- or X-mode; its propagation further inside the plasma is strongly influenced by the plasma parameters. These rather awkward properties make its application somewhat more dicult. In this paper we perform an extensive numerical study of EBW H&CD performance in four typical ST plasmas (NSTX L- and H-mode, MAST Upgrade, NHTX). Coupled ray-tracing (AMR) and Fokker-Planck (LUKE) codes are employed to simulate EBWs of varying frequencies and launch conditions, which are the fundamental EBW parameters that can be chosen and controlled. Our results indicate that an ecient and universal EBW H&CD system is indeed viable. In particular, power can be deposited and current reasonably eciently driven across the whole plasma radius. Such a system could be controlled by a suitably chosen launching antenna vertical position and would also be suciently robust.

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01/01/2011