Pedestal Studies in DIII-D

Journal Article · Sat Oct 15 04:00:00 EDT 2005 · Fusion Science and Technology

OSTI ID:20854278

Groebner, R J ^[1]; Osborne, T H ^[1]; Fenstermacher, M E ^[2]; Leonard, A W ^[1]; Mahdavi, M A ^[1]; Moyer, R A ^[3]; Owen, L W ^[4]; Porter, G D ^[2]; Snyder, P B ^[1]; Stangeby, P C ^[5]; Rhodes, T L ^[3]; Wolf, N S ^[2]

---

1. General Atomics (United States)
2. Lawrence Livermore National Laboratory (United States)
3. University of California (United States)
4. Oak Ridge National Laboratory (United States)
5. University of Toronto (Canada)

Studies of the H-mode pedestal in the DIII-D tokamak are presented. The global energy confinement increases as the plasma pressure on top of the pedestal increases. The best empirical description for a pedestal width parameter is {delta}{sub pe} [proportional to] ({beta}{sub pol}{sup PED}){sup 0.4}, where {delta}{sub pe} is the width of the electron pressure pedestal and {beta}{sub pol}{sup PED} is the poloidal beta at the top of the pedestal. The edge profiles of electron density n{sub e}, electron temperature T{sub e}, and ion temperature T{sub i} can all have different shapes. Thus, a simple width scaling for the edge might not exist, and studies of the physics of individual profiles have been initiated. A model for the n{sub e} profile, based on self-consistent treatment of edge particle sources and edge particle transport, agrees with several experimental observations. The steep gradient region for the T{sub e} profile often extends farther into the plasma than the n{sub e} pedestal step. Magnetohydrodynamic stability provides the ultimate limits to the evolution of the pedestal and usually leads to edge instabilities called edge-localized modes (ELMs). However, the absence of ELMs in a regime called the Quiescent H-mode shows that large pedestals can be produced without ELMs.

• OSTI ID: 20854278
• Journal Information: Fusion Science and Technology, Journal Name: Fusion Science and Technology Journal Issue: 2 Vol. 48; ISSN 1536-1055
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DOUBLET-3 DEVICE
EDGE LOCALIZED MODES
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
H-MODE PLASMA CONFINEMENT
ION TEMPERATURE
PLASMA PRESSURE
QUIESCENT PLASMA
RADIATION TRANSPORT
STABILITY