Abstract
The mission of the National Spherical Torus Experiment ~NSTX! is to extend the understanding of
toroidal physics to low aspect ratio (R/a.1.25) in low collisionality regimes. NSTX is designed to
operate with up to 6 MW of high harmonic fast wave ~HHFW! heating and current drive, 5 MW of
neutral beam injection ~NBI! and co-axial helicity injection ~CHI! for noninductive startup. Initial
experiments focused on establishing conditions that will allow NSTX to achieve its aims of
simultaneous high bt and high-bootstrap current fraction, and to develop methods for noninductive
operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma
currents up to 1 MA and with a range of shapes and configurations were produced. Density limits
in deuterium and helium reached 80% and 120% of the Greenwald limit, respectively. Significant
electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for
up to 200 ms was produced noninductively using CHI. Initial NBI experiments were carried out
with up to two beam sources ~3.2 MW!. Plasmas with stored energies of up to 140 kJ and bt
521% were produced.