Overview of the initial NSTX experimental results

The main aim of the National Spherical Torus Experiment (NSTX) is to establ ish the fusion physics principles of the spherical torus (ST) concept. The NSTX device began plasma operations in February 1999 and the plasma current I-p was successfully brought up to the design value of I MA on 14 December 1999. The planned plasma shaping parameters, elongation kappa = 1.6-2.2 an d, triangularity delta = 0.2-0.4, were achieved in inner wall limited, and single null and double null diverted configurations. The coaxial helicity i njection (CHI) and high harmonic fast wave (HHFW) experiments were also ini tiated. CHI current of 27 kA produced up to 260 kA toroidal current without using an ohmic solenoid. With the injection of 2.3 MW of HHFW power, using 12 antennas connected to six transmitters, electrons, were heated from a c entral temperature of 400 eV to 900 eV at a central density of 3.5 x 10(13) cm(-3), increasing the plasma energy to 59 kJ and the toroidal beta, beta (T), to 10%. The NBI system commenced operation in September 2000. The init ial results with two ion sources (P-NBI = 2.8 MW) show good heating, produc ing a total plasma stored energy of 90 kJ corresponding to beta (T) approxi mate to 18% at a plasma current of 1.1 MA.