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Title: Progress towards Steady State on NSTX

Abstract

In order to reduce recirculating power fraction to acceptable levels, the spherical torus concept relies on the simultaneous achievement of high toroidal {beta} and high bootstrap fraction in steady state. In the last year, as a result of plasma control system improvements, the achievable plasma elongation on the National Spherical Torus Experiment (NSTX) has been raised from {kappa} {approx} 2.1 to {kappa} {approx} 2.6--approximately a 25% increase. This increase in elongation has lead to a doubling increase in the toroidal {beta} for long-pulse discharges. The increase in {beta} is associated with an increase in plasma current at nearly fixed poloidal {beta}, which enables higher {beta}{sub t} with nearly constant bootstrap fraction. As a result, for the first time in a spherical torus, a discharge with a plasma current of 1 MA has been sustained for 1 second. Data is presented from NSTX correlating the increase in performance with increased plasma shaping capability. In addition to improved shaping, H-modes induced during the current ramp phase of the plasma discharge have been used to reduce flux consumption during and to delay the onset of MHD instabilities. A modeled integrated scenario, which has 100% non-inductive current drive with very high toroidal {beta}, willmore » also be presented. The NSTX poloidal field coils are currently being modified to produce the plasma shape which is required for this scenario, which requires high triangularity ({delta} {approx} 0.8) at elevated elongation ({kappa} {approx} 2.5). The other main requirement for steady state on NSTX is the ability to drive a fraction of the total plasma current with radio-frequency waves. The results of High Harmonic Fast Wave heating and current drive studies as well as electron Bernstein Wave emission studies will be presented.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., Princeton, NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
836619
Report Number(s):
PPPL-4044
TRN: US0501127
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: Supercedes report DE00836619; PBD: 24 Jan 2005; PBD: 24 Jan 2005
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CONTROL SYSTEMS; ELECTRIC CURRENTS; ELECTRONS; ELONGATION; HARMONICS; HEATING; NON-INDUCTIVE CURRENT DRIVE; PERFORMANCE; PLASMA; SHAPE; BOOTSTRAP CURRENT; SPHERICAL TORUS; STEADY-STATE FUSION RESEARCH

Citation Formats

D.A. Gates, C. Kessel, J. Menard, G. Taylor, J.R. Wilson, and plus 94 co-authors. Progress towards Steady State on NSTX. United States: N. p., 2005. Web. doi:10.2172/836619.
D.A. Gates, C. Kessel, J. Menard, G. Taylor, J.R. Wilson, & plus 94 co-authors. Progress towards Steady State on NSTX. United States. doi:10.2172/836619.
D.A. Gates, C. Kessel, J. Menard, G. Taylor, J.R. Wilson, and plus 94 co-authors. Mon . "Progress towards Steady State on NSTX". United States. doi:10.2172/836619. https://www.osti.gov/servlets/purl/836619.
@article{osti_836619,
title = {Progress towards Steady State on NSTX},
author = {D.A. Gates and C. Kessel and J. Menard and G. Taylor and J.R. Wilson and plus 94 co-authors},
abstractNote = {In order to reduce recirculating power fraction to acceptable levels, the spherical torus concept relies on the simultaneous achievement of high toroidal {beta} and high bootstrap fraction in steady state. In the last year, as a result of plasma control system improvements, the achievable plasma elongation on the National Spherical Torus Experiment (NSTX) has been raised from {kappa} {approx} 2.1 to {kappa} {approx} 2.6--approximately a 25% increase. This increase in elongation has lead to a doubling increase in the toroidal {beta} for long-pulse discharges. The increase in {beta} is associated with an increase in plasma current at nearly fixed poloidal {beta}, which enables higher {beta}{sub t} with nearly constant bootstrap fraction. As a result, for the first time in a spherical torus, a discharge with a plasma current of 1 MA has been sustained for 1 second. Data is presented from NSTX correlating the increase in performance with increased plasma shaping capability. In addition to improved shaping, H-modes induced during the current ramp phase of the plasma discharge have been used to reduce flux consumption during and to delay the onset of MHD instabilities. A modeled integrated scenario, which has 100% non-inductive current drive with very high toroidal {beta}, will also be presented. The NSTX poloidal field coils are currently being modified to produce the plasma shape which is required for this scenario, which requires high triangularity ({delta} {approx} 0.8) at elevated elongation ({kappa} {approx} 2.5). The other main requirement for steady state on NSTX is the ability to drive a fraction of the total plasma current with radio-frequency waves. The results of High Harmonic Fast Wave heating and current drive studies as well as electron Bernstein Wave emission studies will be presented.},
doi = {10.2172/836619},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 24 00:00:00 EST 2005},
month = {Mon Jan 24 00:00:00 EST 2005}
}

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