High Performance Plasmas on the National Spherical Torus Experiment
Abstract
The National Spherical Torus Experiment has produced toroidal plasmas at low aspect ratio (A = R/a = 0.86m/0.68m roughly 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 seen 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 Beta(t) (=2 mu(sub 0) <p> /B(exp 2) = a measure of magnetic confinement efficiency) of 22% have been achieved, as calculated using the EFIT equilibrium reconstruction code. Beta limiting phenomena have been observed, and the maximum Beta(t) scales with I(sub p/a Beta(t). 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 2.0keV 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2001
- Accession Number
- ADA638816
Entities
People
- D. A. Gates
- D. Darrow
- J. Bialek
- J. Ferron
- M. Bitter
- M. G. Bell
- P. Bonoli
- P. C. Efthimion
- R. E. Bell
- T. Bigelow
Organizations
- Princeton University