Abstract
Off-axis electron Bernstein wave current drive (EBWCD) may be critical for sustaining non-inductive high β NSTX plasmas. Numerical modeling results predict that the ~ 100 kA of offaxis current needed to stabilize a solenoid-free high β NSTX plasma could be generated via Ohkawa CD with 3 MW of 28 GHz EBW power. In addition, synergy between EBWCD and bootstrap current may result in a 10% enhancement in CD efficiency with 4 MW of EBW power. Recent dualpolarization EBW radiometry measurements on NSTX confirm that efficient coupling to EBWs can be readily accomplished by launching elliptically polarized electromagnetic waves oblique to the confining magnetic field, in agreement with numerical modeling. Plans are being developed for implementing a 1 MW, 28 GHz proof-of-principle EBWCD system on NSTX to test the EBW coupling, heating and CD physics at high rf power densities.
