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Title: Development of NSTX Particle Control Techniques

Abstract

The National Spherical Torus Experiment (NSTX) High Harmonic Fast Wave (HHFW) current-drive discharges will require density control for acceptable efficiency. In NSTX, this involves primarily controlling impurity influxes and recycling. We have compared boronization on hot and cold surfaces, varying helium glow discharge conditioning (HeGDC) durations, helium discharge cleaning, brief daily boronization, and between discharge boronization to reduce and control spontaneous density rises. Access to Ohmic H-modes was enabled by boronization on hot surfaces, however, the duration of the effectiveness of hot and cold boronization was comparable. A 15 minute HeGDC between discharges was needed for reproducible L-H transitions. Helium discharge conditioning yielded slower density rises than 15 minutes of HeGDC. Brief daily boronization followed by a comparable duration of applied HeGDC restored and enhanced good conditions. Additional brief boronizations between discharges did not improve plasma performance (reduced recycling, reduced impurity luminosities, earlier L-H transitions, longer plasma current flattops, higher stored energies) if conditions were already good. Between discharge boronization required increases in the NSTX duty cycle due to the need for additional HeGDC to remove codeposited D.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., Princeton, NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
828583
Report Number(s):
PPPL-3989
TRN: US0404032
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 30 Jul 2004
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CLEANING; EFFICIENCY; ELECTRIC CURRENTS; GLOW DISCHARGES; HARMONICS; HELIUM; PERFORMANCE; PLASMA; RECYCLING; IMPURITIES; PLASMA-WALL INTERACTION; TOKAMAKS, NSTX

Citation Formats

H.W. Kugel, R. Maingi, M. Bell, D. Gates, K. Hill, B. LeBlanc, D. Mueller, R. Kaita, S. Paul, S. Sabbagh, C.H. Skinner, V. Soukhanovskii, B. Stratton, and R. Raman. Development of NSTX Particle Control Techniques. United States: N. p., 2004. Web. doi:10.2172/828583.
H.W. Kugel, R. Maingi, M. Bell, D. Gates, K. Hill, B. LeBlanc, D. Mueller, R. Kaita, S. Paul, S. Sabbagh, C.H. Skinner, V. Soukhanovskii, B. Stratton, & R. Raman. Development of NSTX Particle Control Techniques. United States. doi:10.2172/828583.
H.W. Kugel, R. Maingi, M. Bell, D. Gates, K. Hill, B. LeBlanc, D. Mueller, R. Kaita, S. Paul, S. Sabbagh, C.H. Skinner, V. Soukhanovskii, B. Stratton, and R. Raman. Fri . "Development of NSTX Particle Control Techniques". United States. doi:10.2172/828583. https://www.osti.gov/servlets/purl/828583.
@article{osti_828583,
title = {Development of NSTX Particle Control Techniques},
author = {H.W. Kugel and R. Maingi and M. Bell and D. Gates and K. Hill and B. LeBlanc and D. Mueller and R. Kaita and S. Paul and S. Sabbagh and C.H. Skinner and V. Soukhanovskii and B. Stratton and R. Raman},
abstractNote = {The National Spherical Torus Experiment (NSTX) High Harmonic Fast Wave (HHFW) current-drive discharges will require density control for acceptable efficiency. In NSTX, this involves primarily controlling impurity influxes and recycling. We have compared boronization on hot and cold surfaces, varying helium glow discharge conditioning (HeGDC) durations, helium discharge cleaning, brief daily boronization, and between discharge boronization to reduce and control spontaneous density rises. Access to Ohmic H-modes was enabled by boronization on hot surfaces, however, the duration of the effectiveness of hot and cold boronization was comparable. A 15 minute HeGDC between discharges was needed for reproducible L-H transitions. Helium discharge conditioning yielded slower density rises than 15 minutes of HeGDC. Brief daily boronization followed by a comparable duration of applied HeGDC restored and enhanced good conditions. Additional brief boronizations between discharges did not improve plasma performance (reduced recycling, reduced impurity luminosities, earlier L-H transitions, longer plasma current flattops, higher stored energies) if conditions were already good. Between discharge boronization required increases in the NSTX duty cycle due to the need for additional HeGDC to remove codeposited D.},
doi = {10.2172/828583},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jul 30 00:00:00 EDT 2004},
month = {Fri Jul 30 00:00:00 EDT 2004}
}

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