Possible achievement of second stability by means of lower hybrid current drive

Abstract

It is shown that radial profiles of the safety factor q(r), necessary to access the socalled "second stability" regime in shaped, low aspect ratio tokamnaks, can be achieved via off-axis lower hybrid current drive (LHCD). In order to accurately model the required current profiles, our previous simulation code for LHCD has been extended to noncircular equilibria and combined with an MHD equilibrium solver. As a particular example, results will be presented for Versator Upgrade tokamak parameters.

Advanced Tokamak Plasmas in the Fusion Ignition Research Experiment

“…The lower hybrid current drive calculations were done with LSC [9], ACCOME [10], and CURRAY [11]. The minimum frequency was chosen to be above twice the maximum lower hybrid frequency expected.…”

Enhanced Lower Hybrid Penetration Via Intense Multi-Microsecond Pulses

“…The opacity for both regimes A and B and the nonlinear plateau width have been incorporated into the ACCOME ray-tracing and current-drive code which was developed within the framework of LLNL-MIT-JAERI collaboration [7]. The code evaluates power deposition as a function of flux surface for model temperature and density profiles and numerically computed equilibria.…”

Fusion development and technology

“…Our first success [2] reported on the production of superconducting P/M wire, in which we used Nb or Nb(Ti) powder in combination with Sn(Ga) powder. The Ti and Ga additions concern small amounts, that are in solid solution in the Nb and Sn respectively.…”

“…Alfv_n Eigenmodes (EAE) with the previously known Toroidal Alfv_n Eigenmodes (TAE) (in circular cross section plasmas) necessitated an investigation for spe(:ific ITER geometry and parameters. This was done by working out the malginal stability curves in n-T space first without and then including important continuum damping effects [2]. While the TAE may be stable, the EAE has a significant instability region in n-T operating space.…”