Initial Results from the National Spherical Torus Experiment (NSTX)

With a small, high-power density, and compact fusion core, Spherical Tori (ST) can provide an attractive path to a reactor or a volumetric neutron source. The National Spherical Torus Experiment (NSTX) is a proof-of-principle experiment that will explore the physics of low aspect ratio in scientifically interesting and aggressive regimes. To accomplish this mission, NSTX is designed to produce plasmas with R/a = 0.85 m/0.68 m {approximately} 1.25, I{sub p} = 1 MA, B{sub T} {le} 0.6 T, {kappa} {le} 2.2, {delta} {le} 0.5, heating powers of up to 11 MW (6 MW High Harmonic Fast Waves, 5 MW, 80 keV, D{sup 0} Neutral Beam Injection), and operation over a wide range of shapes and configurations. The OH solenoid and PF coils on NSTX are capable of producing approximately 1 V-sec of inductive flux, which, alone, is sufficient for plasma breakdown and for increasing the plasma current to the MA level. Breakdown, however, will be assisted by EC preionization. Co-axial Helicity Injection (CHI){sup 4} provides the opportunity for V-sec savings during breakdown as well as for completely non-inductive startup to about 500 kA