Abstract
The main aim of the National Spherical Torus Experiment (NSTX) is to establish the
fusion physics principles of the spherical torus (ST) concept. The NSTX device began plasma operations
in February 1999 and the plasma current Ip was successfully brought up to the design value
of 1 MA on 14 December 1999. The planned plasma shaping parameters, elongation = 1:6{2.2
and triangularity = 0:2{0.4, were achieved in inner wall limited, and single null and double null
diverted con gurations. The coaxial helicity injection (CHI) and high harmonic fast wave (HHFW)
experiments were also initiated. 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 central temperature of 400 eV to 900 eV at a central
density of 3:5 1013 cm
3, increasing the plasma energy to 59 kJ and the toroidal , T , to 10%.
The NBI system commenced operation in September 2000. The initial results with two ion sources
(PNBI = 2:8 MW) show good heating, producing a total plasma stored energy of 90 kJ corresponding
to T 18% at a plasma current of 1.1 MA.