The National Spherical Torus Experiment (NSTX) offers an operational space characterized by high-beta (βt ≤ 39%, βN > 7, ) and low aspect ratio (A > 1.27) to leverage the plasma parameter dependences of RWM stabilization and plasma rotation damping physics giving greater confidence for extrapolation to ITER. Significant new capability for RWM research has been added to the device with the commissioning of a set of six non-axisymmetric magnetic field coils, allowing generation of fields with dominant toroidal mode number, n, of 1-3. These coils have been used to study the dependence of resonant field amplification on applied field frequency and RWM stabilization physics by reducing the toroidal rotation profile below its steady-state value through non-resonant magnetic braking. Modification of plasma rotation profiles shows that rotation outside q ≤ 2.5 is not required for passive RWM stability and there is large variation in the RWM critical rotation at the q ≤ 2 surface, both of which are consistent with distributed dissipation models.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Condensed Matter Physics