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Title: Advances in understanding quiescent H-mode plasmas in DIII-D

Abstract

Recent QH-mode research on DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] has used the peeling-ballooning modes model of edge magnetohydrodynamic stability as a working hypothesis to organize the data; several predictions of this theory are consistent with the experimental results. Current ramping results indicate that QH modes operate near the edge current limit set by peeling modes. This operating point explains why QH mode is easier to get at lower plasma currents. Power scans have shown a saturation of edge pressure with increasing power input. This allows QH-mode plasmas to remain stable to edge localized modes (ELMs) to the highest powers used in DIII-D. At present, the mechanism for this saturation is unknown; if the edge harmonic oscillation (EHO) is playing a role here, the physics is not a simple amplitude dependence. The increase in edge stability with plasma triangularity predicted by the peeling-ballooning theory is consistent with the substantial improvement in pedestal pressure achieved by changing the plasma shape from a single null divertor to a high triangularity double null. Detailed ELITE calculations for the high triangularity plasmas have demonstrated that themore » plasma operating point is marginally stable to peeling-ballooning modes. Comparison of ELMing, coinjected and quiescent, counterinjected discharges with the same shape, current, toroidal field, electron density, and electron temperature indicates that the edge radial electric field or the edge toroidal rotation are also playing a role in edge stability. The EHO produces electron, main ion, and impurity particle transport at the plasma edge which is more rapid than that produced by ELMs under similar conditions. The EHO also decreases the edge rotation while producing little change in the edge electron and ion temperatures. Other edge electromagnetic modes also produce particle transport; this includes the incoherent, broadband activity seen at high triangularity. Pedestal values of {nu}{sub *} and {beta}{sub T} bracketing, those required for International Experimental Thermonuclear Reactor [Nucl. Fusion 39, 2137 (1999)] have been achieved in DIII-D, demonstrating the QH-mode edge densities are sufficient for future devices.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;  [1]; ; ; ;  [2];  [3]; ;  [4]
  1. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
  2. University of California-Los Angeles, Los Angeles, California 90024 (United States)
  3. University of Texas-Austin, Austin, Texas 78712 (United States)
  4. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
Publication Date:
OSTI Identifier:
20736586
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 12; Journal Issue: 5; Other Information: DOI: 10.1063/1.1894745; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALLOONING INSTABILITY; DOUBLET-3 DEVICE; EDGE LOCALIZED MODES; H-MODE PLASMA CONFINEMENT; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA DENSITY; PLASMA IMPURITIES; PLASMA PRESSURE; PLASMA WAVES

Citation Formats

Burrell, K H, West, W P, Gohil, P, Greenfield, C M, Groebner, R J, Hyatt, A W, Kaplan, D H, Lao, L L, Leonard, A W, Osborne, T H, Snyder, P B, Thomas, D M, Strait, E J, Doyle, E J, Rhodes, T L, Wang, G, Zeng, L, Austin, M E, Casper, T A, and Jayakumar, R J. Advances in understanding quiescent H-mode plasmas in DIII-D. United States: N. p., 2005. Web. doi:10.1063/1.1894745.
Burrell, K H, West, W P, Gohil, P, Greenfield, C M, Groebner, R J, Hyatt, A W, Kaplan, D H, Lao, L L, Leonard, A W, Osborne, T H, Snyder, P B, Thomas, D M, Strait, E J, Doyle, E J, Rhodes, T L, Wang, G, Zeng, L, Austin, M E, Casper, T A, & Jayakumar, R J. Advances in understanding quiescent H-mode plasmas in DIII-D. United States. doi:10.1063/1.1894745.
Burrell, K H, West, W P, Gohil, P, Greenfield, C M, Groebner, R J, Hyatt, A W, Kaplan, D H, Lao, L L, Leonard, A W, Osborne, T H, Snyder, P B, Thomas, D M, Strait, E J, Doyle, E J, Rhodes, T L, Wang, G, Zeng, L, Austin, M E, Casper, T A, and Jayakumar, R J. Sun . "Advances in understanding quiescent H-mode plasmas in DIII-D". United States. doi:10.1063/1.1894745.
@article{osti_20736586,
title = {Advances in understanding quiescent H-mode plasmas in DIII-D},
author = {Burrell, K H and West, W P and Gohil, P and Greenfield, C M and Groebner, R J and Hyatt, A W and Kaplan, D H and Lao, L L and Leonard, A W and Osborne, T H and Snyder, P B and Thomas, D M and Strait, E J and Doyle, E J and Rhodes, T L and Wang, G and Zeng, L and Austin, M E and Casper, T A and Jayakumar, R J},
abstractNote = {Recent QH-mode research on DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] has used the peeling-ballooning modes model of edge magnetohydrodynamic stability as a working hypothesis to organize the data; several predictions of this theory are consistent with the experimental results. Current ramping results indicate that QH modes operate near the edge current limit set by peeling modes. This operating point explains why QH mode is easier to get at lower plasma currents. Power scans have shown a saturation of edge pressure with increasing power input. This allows QH-mode plasmas to remain stable to edge localized modes (ELMs) to the highest powers used in DIII-D. At present, the mechanism for this saturation is unknown; if the edge harmonic oscillation (EHO) is playing a role here, the physics is not a simple amplitude dependence. The increase in edge stability with plasma triangularity predicted by the peeling-ballooning theory is consistent with the substantial improvement in pedestal pressure achieved by changing the plasma shape from a single null divertor to a high triangularity double null. Detailed ELITE calculations for the high triangularity plasmas have demonstrated that the plasma operating point is marginally stable to peeling-ballooning modes. Comparison of ELMing, coinjected and quiescent, counterinjected discharges with the same shape, current, toroidal field, electron density, and electron temperature indicates that the edge radial electric field or the edge toroidal rotation are also playing a role in edge stability. The EHO produces electron, main ion, and impurity particle transport at the plasma edge which is more rapid than that produced by ELMs under similar conditions. The EHO also decreases the edge rotation while producing little change in the edge electron and ion temperatures. Other edge electromagnetic modes also produce particle transport; this includes the incoherent, broadband activity seen at high triangularity. Pedestal values of {nu}{sub *} and {beta}{sub T} bracketing, those required for International Experimental Thermonuclear Reactor [Nucl. Fusion 39, 2137 (1999)] have been achieved in DIII-D, demonstrating the QH-mode edge densities are sufficient for future devices.},
doi = {10.1063/1.1894745},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 12,
place = {United States},
year = {2005},
month = {5}
}