Abstract
The National Spherical Torus Experiment has produced
toroidal plasmas at low aspect ratio (A = R/a =
0.86d0.68m - 1.3, where R is the major radius and a is
the minor radius of the torus) with plasma currents of
1.4MA. The rapid development of the machine has led to
very exciting physics results during the first full year of
physics operation. Pulse lengths in excess of 0.5s have
been obtained with inductive current drive. Up to 4MW
of High Harmonic Fast Wave (HHFW) heating power has
been applied with 6MW planned. Using only 2MW of
HHFW heating power clear evidence of electron heating
is sden with HHFW, as observed by the multi point
Thomson scattering diagnostic. A non-inductive current
drive concept known as Coaxial Helicity Injection (CHI)
has driven 260kA of toroidal current. Neutral beam
heating power of 5MW has been injected. Plasmas with
PI ( =2p0<p>/B2 = a measure of magnetic confinement
efficiency) of 22% have been achieved, as calculated
using the EFIT equilibrium reconstruction code. P
limiting phenomena have been observed, and the
maximum p, scales with I&z& High frequency (>MHz)
magnetic fluctuations have been observed. H-mode
plasmas are observed with confinement times of >
100ms. Beam heated plasmas show energy confinement
times in excess of those predicted by empirical scaling
expressions. Ion temperatures in excess of 2.OkeV have
been measured, and power balance suggests that the
power loss from the ions to the electrons may exceed the
calculated classical input power to the ions.