Engineering design of the National Spherical Torus Experiment

Abstract

NSTX is a proof-of-principle experiment aimed at exploring the physics of the "spherical torus" (ST) configuration, which is predicted to exhibit more efficient magnetic confinement than conventional large aspect ratio tokamaks, amongst other advantages. The low aspect ratio (R/a, typically 1.2 2 in ST designs compared to 4 ~ 5 in conventional tokamaks) decreases the available cross sectional area through the center of the torus for toroidal and poloidal field coil conductors, vacuum vessel wall, plasma facing components, etc., thus increasing the need to deploy all components within the so-called "center stack" in the most efficient manner possible. Several unique design features have been developed for the NSTX center stack, and careful engineering of this region of the machine, utilizing materials up to their engineering allowables, has been key to meeting the desired objectives. The design and construction of the machine has been accomplished in a rapid and cost effective manner thanks to the availability of extensive facilities, a strong experience base from the TFTR era, and good cooperation between institutions.

Recent results from the National Spherical Torus Experiment

“…The National Spherical Torus Experiment (NSTX) is a low aspect-ratio fusion research facility [1,2] (R = 0.86 m, a = 0.67 m, R/a 1.26, B t 0.6 T, I p 1.5 MA) which commenced physics operation in July 1999. A cross-section of the device is shown in figure 1.…”

Effect of Boronization on Ohmic Plasmas in NSTX

“…The National Spherical Torus Experiment (NSTX) [11] began operations in February 1999. The research program is aimed at extending the understanding toroidal confinement physics at low aspect ratio in collisionless, high-β regimes and to demonstrate non-inductive current generation and sustainment [12,13].…”

Plasma shape control on the National Spherical Torus Experiment (NSTX) using real-time equilibrium reconstruction

“…Data acquisition functions were customized for compatibility with the FPDP data acquisition system described above, and this functionality has been separated from the PCS. Another important feature of the NSTX implementation of the PCS is that power supply control functions are handled digitally -with individual rectifier firing angles generated within a stand-alone program called the Power Supply Real-Time controller (PSRTC) [11].…”