Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak

High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can...

Full description

Saved in:
Bibliographic Details
Published in:Physics of Plasmas 2001-05, Vol.8 (5), p.2153-2162
Main Authors: Burrell, K. H., Austin, M. E., Brennan, D. P., DeBoo, J. C., Doyle, E. J., Fenzi, C., Fuchs, C., Gohil, P., Greenfield, C. M., Groebner, R. J., Lao, L. L., Luce, T. C., Makowski, M. A., McKee, G. R., Moyer, R. A., Petty, C. C., Porkolab, M., Rettig, C. L., Rhodes, T. L., Rost, J. C., Stallard, B. W., Strait, E. J., Synakowski, E. J., Wade, M. R., Watkins, J. G., West, W. P.
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation that is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 s or >25 energy confinement times τ E ), yielding a quiescent double barrier regime. By slowly ramping the input power, we have achieved β N H 89 =7 for up to 5 times the τ E of 150 ms. The β N H 89 values of 7 substantially exceed the value of 4 routinely achieved in the standard ELMing H mode. The key factors in creating the quiescent H-mode operation are neutral beam injection in the direction opposite to the plasma current (counter injection) plus cryopumping to reduce the density. Density and impurity control in the quiescent H mode is possible because of the presence of an edge magnetohydrodynamic (MHD) oscillation, the edge harmonic oscillation, which enhances the edge particle transport while leaving the energy transport unaffected.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.1355981