Published: 2001
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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.