Hot-Ion Distribution Function in the Oak Ridge Tokamak

Observed Doppler shifts of neutral-hydrogen ${\mathrm{H}}_{\alpha }$ radiation in the poloidal and toroidal directions in the Oak Ridge tokamak experiment are shown to be consistent with neoclassical theory. The inferred shift and distortion of the proton distribution function in the banana-plateau regime is caused by the radial pressure gradient and by the ambipolar electric field, whose steady-state value is determined by nonambipolar diffusion due to charge exchange.