Progress in understanding the enhanced pedestal H-mode in NSTX
Abstract
The paper describes the enhanced pedestal (EP) H-mode observed in the National Spherical Torus Experiment (NSTX). The defining characteristics of EP H-mode are given, namely i)transition after the L- to H-mode transition, ii) region of very steep ion temperature gradient, and iii) associated region of strong rotational shear. A newly observed long-pulse EP H-mode example shows quiescent behavior for as long as the heating and current drive sources are maintained. Cases are shown where the region of steep ion temperature gradient is located at the very edge, and cases where it is shifted up to 10 cm inward from the plasma edge; these cases are united by a common dependence of the ion temperature gradient on the toroidal rotation frequency shear. EP H-mode examples have been observed across a wide range of q95 and pedestal collisionality. No strong changes in the fluctuation amplitudes have been observed following the eP H-mode transition, and transport analysis indicates that the ion t hermal transport is comparable to or less than anticipated from a simple neoclassical transport model. Cases are shown where EP H-modes were reliably generated, through these low-q95 examples were difficult to sustain. A case where an externally triggered ELM precipitates themore »
- Authors:
-
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Univ. of Wisconsin, Madison, WI (United States) Dept. of Engineering Physics
- Nova Phontonics, Princeton, NJ (Unitied States)
- Columbia Univ., New York, NY (United States) Dept. of Applied Physics
- Publication Date:
- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1164217
- Report Number(s):
- PPPL-5031
Journal ID: ISSN 0029-5515; PPPL-5031
- Grant/Contract Number:
- AC02-09CH11466
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 54; Journal Issue: 8; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EP H-MODE; H-MODE; NSTX; SPHERICAL TORUS
Citation Formats
Gerhardt, S. P., Canik, J. M., Maingi, R., Battaglia, D., Bell, R. E., Guttenfelder, W., LeBlanc, B. P., Smith, D. R., Yuh, H., and Sabbagh, S. Progress in understanding the enhanced pedestal H-mode in NSTX. United States: N. p., 2014.
Web. doi:10.1088/0029-5515/54/8/083021.
Gerhardt, S. P., Canik, J. M., Maingi, R., Battaglia, D., Bell, R. E., Guttenfelder, W., LeBlanc, B. P., Smith, D. R., Yuh, H., & Sabbagh, S. Progress in understanding the enhanced pedestal H-mode in NSTX. United States. https://doi.org/10.1088/0029-5515/54/8/083021
Gerhardt, S. P., Canik, J. M., Maingi, R., Battaglia, D., Bell, R. E., Guttenfelder, W., LeBlanc, B. P., Smith, D. R., Yuh, H., and Sabbagh, S. Fri .
"Progress in understanding the enhanced pedestal H-mode in NSTX". United States. https://doi.org/10.1088/0029-5515/54/8/083021. https://www.osti.gov/servlets/purl/1164217.
@article{osti_1164217,
title = {Progress in understanding the enhanced pedestal H-mode in NSTX},
author = {Gerhardt, S. P. and Canik, J. M. and Maingi, R. and Battaglia, D. and Bell, R. E. and Guttenfelder, W. and LeBlanc, B. P. and Smith, D. R. and Yuh, H. and Sabbagh, S.},
abstractNote = {The paper describes the enhanced pedestal (EP) H-mode observed in the National Spherical Torus Experiment (NSTX). The defining characteristics of EP H-mode are given, namely i)transition after the L- to H-mode transition, ii) region of very steep ion temperature gradient, and iii) associated region of strong rotational shear. A newly observed long-pulse EP H-mode example shows quiescent behavior for as long as the heating and current drive sources are maintained. Cases are shown where the region of steep ion temperature gradient is located at the very edge, and cases where it is shifted up to 10 cm inward from the plasma edge; these cases are united by a common dependence of the ion temperature gradient on the toroidal rotation frequency shear. EP H-mode examples have been observed across a wide range of q95 and pedestal collisionality. No strong changes in the fluctuation amplitudes have been observed following the eP H-mode transition, and transport analysis indicates that the ion t hermal transport is comparable to or less than anticipated from a simple neoclassical transport model. Cases are shown where EP H-modes were reliably generated, through these low-q95 examples were difficult to sustain. A case where an externally triggered ELM precipitates the transition to EP H-mode is also shown, though an initial experiment designed to trigger EP-H-modes in this fashion was successful.},
doi = {10.1088/0029-5515/54/8/083021},
journal = {Nuclear Fusion},
number = 8,
volume = 54,
place = {United States},
year = {Fri Aug 01 00:00:00 EDT 2014},
month = {Fri Aug 01 00:00:00 EDT 2014}
}
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Works referencing / citing this record:
Enhanced H-mode pedestals with lithium injection in DIII-D
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