Open AccessInitial Physics Results From the National Spherical Torus Experiment
Author(s) -
S M Kaye,
M G Bell,
R E Bell,
J Bialek
Publication year - 2001
Language(s) - English
Resource type - Reports
DOI - 10.2172/773182
Subject(s) - collisionality , toroid , torus , physics , neutral beam injection , atomic physics , joule heating , bootstrap current , current (fluid) , plasma , harmonic , beam (structure) , computational physics , range (aeronautics) , helium , nuclear physics , tokamak , materials science , optics , geometry , mathematics , quantum mechanics , composite material , thermodynamics
The mission of the National Spherical Torus Experiment (NSTX) is to extend the understanding of toroidal physics to low aspect ratio (R/a approximately equal to 1.25) in low collisionality regimes. NSTX is designed to operate with up to 6 MW of High Harmonic Fast Wave (HHFW) heating and current drive, 5 MW of Neutral Beam Injection (NBI) and Co-Axial Helicity Injection (CHI) for non-inductive startup. Initial experiments focused on establishing conditions that will allow NSTX to achieve its aims of simultaneous high-bt and high-bootstrap current fraction, and to develop methods for non-inductive operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma currents up to 1 MA and with a range of shapes and configurations were produced. Density limits in deuterium and helium reached 80% and 120% of the Greenwald limit respectively. Significant electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for up to 200 msec was produced noninductively using CHI. Initial NBI experiments were carried out with up to two beam sources (3.2 MW). Plasmas with stored energies of up to 140 kJ and bt =21% were produced