Ohmic flux consumption during initial operation of the NSTX spherical torus

Spherical tokamaks, because of their blender central columns, have very lim ited volt second capability relative to that of standard aspect ratio tokam aks of similar plasma cross-section. Recent experiments on NSTX have begun to quantify and optimize the ohmic current drive efficiency in an MA class ST device. Sustainable ramp rates in excess of 5 MA/s during the current ri se phase have been achieved on NSTX, while faster ramps generate significan t MHD activity. Discharges with I-p exceeding 1 MA have been achieved in NS TX with nominal parameters: aspect ratio A = 1.3 1.4, elongation kappa = 2- 2.2, triangularity delta = 0.4, internal inductance l(i) = 0.6, Ejima coeff icient C-E = 0.35. Flux consumption efficiency results, performance improve ments associated with first boronization and comparisons with neoclassical resistivity are described.