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Title: Solenoid-free startup experiments in DIII-D

Abstract

A series of DIII-D experiments was performed to investigate the potential for initiating plasma current using only poloidal field coils located outside the DIII-D central solenoid, i.e. 'solenoid-free'. Plasma current to 166 kA was achieved using 2-3MW of electron cyclotron (EC) heating and was limited by coil and power supply constraints. Flux conversion to plasma current was similar to standard DIII-D startup with some degradation at higher plasma current associated with stray fields and vertical stability issues. In preliminary solenoid-free experiments, neutral beam (NB) current drive (CD) levels were small and attributed to reduced CD efficiency associated with low electron temperature produced by the low current, low confinement plasma. Lack of plasma radial position control also contributed to a reduction of NBCD. Similarly, ECCD was small owing to low plasma temperature and outside EC launch which is required in the solenoid-free scenario. Synergistic experiments were carried out using standard solenoid initiated plasmas in order to study noninductive CD in limited, Lmode plasmas, typical of that generated by solenoid-free startup. While substantial noninductive current can be driven, self-sustaining levels of noninductive current have not yet been achieved with our present six-source co-injection NB system combined with EC and fast wave systems.more » At low plasma current and high levels of localized EC heating, substantial MHD is generated and this was seen to severely limit plasma performance. Although further optimization is possible in the limited plasma regime, full noninductive, steady-state operation may require diverted plasma with H-mode quality confinement. Discharges obtained during the solenoid-free campaign are compared with results of previous DIII-D campaigns aimed at achieving a steady state, noninductive CD solution.« less

Authors:
 [1];  [2];  [3];  [1];  [1];  [1];  [1];  [4];  [1];  [1];  [1];  [4];  [1];  [1];  [3];  [3];  [3];  [5];  [5];  [5] more »;  [6];  [7];  [8];  [8] « less
  1. General Atomics, San Diego
  2. EURATOM CCFE Fus Assoc, Culham Sci Ctr, Abingdon, Oxon, England
  3. Princeton Plasma Physics Laboratory (PPPL)
  4. General Atomics
  5. National Fusion Research Institute, Daejon, South Korea
  6. University of California, San Diego
  7. ORNL
  8. Oak Ridge National Laboratory (ORNL)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1036678
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 51; Journal Issue: 6; Journal ID: ISSN 0029--5515
Country of Publication:
United States
Language:
English
Subject:
TOKAMAK GEOMETRY; FACILITY; OPERATION; PLASMAS; MAST

Citation Formats

Leuer, J A, Cunningham, G, Mueller, D, Brooks, N H, Eldietis, N W, Humphreys, D A, Hyatt, A W, Jackson, G L, Lohr, J, Politzer, P A, Pinsker, R I, Prater, R, Taylor, P L, Walker, M L, Budny, R V, Gates, D A, Nagy, Alex, Hahn, S H, Oh, Y K, Yoon, S W, Yu, J H, Murakami, Masanori, Park, J M, and Sontag, A C. Solenoid-free startup experiments in DIII-D. United States: N. p., 2011. Web. doi:10.1088/0029-5515/51/6/063038.
Leuer, J A, Cunningham, G, Mueller, D, Brooks, N H, Eldietis, N W, Humphreys, D A, Hyatt, A W, Jackson, G L, Lohr, J, Politzer, P A, Pinsker, R I, Prater, R, Taylor, P L, Walker, M L, Budny, R V, Gates, D A, Nagy, Alex, Hahn, S H, Oh, Y K, Yoon, S W, Yu, J H, Murakami, Masanori, Park, J M, & Sontag, A C. Solenoid-free startup experiments in DIII-D. United States. https://doi.org/10.1088/0029-5515/51/6/063038
Leuer, J A, Cunningham, G, Mueller, D, Brooks, N H, Eldietis, N W, Humphreys, D A, Hyatt, A W, Jackson, G L, Lohr, J, Politzer, P A, Pinsker, R I, Prater, R, Taylor, P L, Walker, M L, Budny, R V, Gates, D A, Nagy, Alex, Hahn, S H, Oh, Y K, Yoon, S W, Yu, J H, Murakami, Masanori, Park, J M, and Sontag, A C. 2011. "Solenoid-free startup experiments in DIII-D". United States. https://doi.org/10.1088/0029-5515/51/6/063038.
@article{osti_1036678,
title = {Solenoid-free startup experiments in DIII-D},
author = {Leuer, J A and Cunningham, G and Mueller, D and Brooks, N H and Eldietis, N W and Humphreys, D A and Hyatt, A W and Jackson, G L and Lohr, J and Politzer, P A and Pinsker, R I and Prater, R and Taylor, P L and Walker, M L and Budny, R V and Gates, D A and Nagy, Alex and Hahn, S H and Oh, Y K and Yoon, S W and Yu, J H and Murakami, Masanori and Park, J M and Sontag, A C},
abstractNote = {A series of DIII-D experiments was performed to investigate the potential for initiating plasma current using only poloidal field coils located outside the DIII-D central solenoid, i.e. 'solenoid-free'. Plasma current to 166 kA was achieved using 2-3MW of electron cyclotron (EC) heating and was limited by coil and power supply constraints. Flux conversion to plasma current was similar to standard DIII-D startup with some degradation at higher plasma current associated with stray fields and vertical stability issues. In preliminary solenoid-free experiments, neutral beam (NB) current drive (CD) levels were small and attributed to reduced CD efficiency associated with low electron temperature produced by the low current, low confinement plasma. Lack of plasma radial position control also contributed to a reduction of NBCD. Similarly, ECCD was small owing to low plasma temperature and outside EC launch which is required in the solenoid-free scenario. Synergistic experiments were carried out using standard solenoid initiated plasmas in order to study noninductive CD in limited, Lmode plasmas, typical of that generated by solenoid-free startup. While substantial noninductive current can be driven, self-sustaining levels of noninductive current have not yet been achieved with our present six-source co-injection NB system combined with EC and fast wave systems. At low plasma current and high levels of localized EC heating, substantial MHD is generated and this was seen to severely limit plasma performance. Although further optimization is possible in the limited plasma regime, full noninductive, steady-state operation may require diverted plasma with H-mode quality confinement. Discharges obtained during the solenoid-free campaign are compared with results of previous DIII-D campaigns aimed at achieving a steady state, noninductive CD solution.},
doi = {10.1088/0029-5515/51/6/063038},
url = {https://www.osti.gov/biblio/1036678}, journal = {Nuclear Fusion},
issn = {0029--5515},
number = 6,
volume = 51,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 2011},
month = {Sat Jan 01 00:00:00 EST 2011}
}