Open AccessOhmic Flux Consumption During Initial Operation of the NSTX Spherical Torus
Author(s) -
J. Ménard,
B. LeBlanc,
S.A. Sabbagh,
M. Bell,
R. E. Bell,
E. Fredrickson,
D. Gates,
S.C. Jardin,
S. Kaye,
H. Kugel,
R. Maingi,
R. Maqueda,
D. Mueller,
M. Ono,
Shashi Paul,
C. H. Skinner,
D. Stutman
Publication year - 2000
Publication title -
osti oai (u.s. department of energy office of scientific and technical information)
Language(s) - English
Resource type - Reports
DOI - 10.2172/764943
Subject(s) - spherical tokamak , tokamak , ohmic contact , plasma , bootstrap current , torus , flux (metallurgy) , materials science , joule heating , physics , electrical resistivity and conductivity , atomic physics , nuclear engineering , mechanics , nuclear physics , geometry , nanotechnology , composite material , mathematics , engineering , metallurgy , quantum mechanics , layer (electronics)
The spherical tokamak (ST), because of its slender central column, has very limited volt-second capability relative to a standard aspect ratio tokamak of similar plasma cross-section. Recent experiments on the National Spherical Torus Experiment (NSTX) have begun to quantify and optimize the ohmic current drive efficiency in a MA-class ST device. Sustainable ramp-rates in excess of 5MA/sec during the current rise phase have been achieved on NSTX, while faster ramps generate significant MHD activity. Discharges with Ip exceeding 1MA have been achieved in NSTX with nominal parameters: aspect ratio A=1.3--1.4, elongation k=2--2.2, triangularity d=0.4, internal inductance li=0.6, and Ejima coefficient CE=0.35. Flux consumption efficiency results, performance improvements associated with first boronization, and comparisons to neoclassical resistivity are described
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