Observation of ultra low q equilibrium

Abstract
The characteristics of a toroidal discharge with qa ≈ 1/2 is studied on TORIUT-6. Ultra low q equilibria that are stable against the global kink mode are realized through MHD relaxation and are shown to be characterized by dq/dr < 0 and a hollow current profile. The stable state lasts for 600 μs, which is of the order of the classical diffusion time. These experimental observations are consistent with non-linear MHD simulation results.