Chapter 6: H-Mode and Pedestal Physics in ASDEX Upgrade
- Max-Planck-Institut fuer Plasmaphysik (Germany)
Studies in ASDEX Upgrade of the phenomenology and scaling of the H-mode transition, of edge-localized modes (ELMs), and characterization of the H-mode edge transport barrier carried out in various experimental campaigns between 1996 and 2001 are described. The H-mode transition is recognized by formation of a radial electrical field at the plasma boundary, which in ASDEX Upgrade is detected by an associated increase of the neutral particle charge exchange flux from ripple trapped particles. A scaling for the critical local edge temperature for the H-mode transition threshold is found. Similarity experiments with ASDEX Upgrade and Joint European Torus plasmas for the H-mode transition indicate that the H-mode transition can be obtained at the same values of dimensionless parameters {rho}{sup *}, {nu}{sup *}, and {beta} at the plasma edge, indicating that the threshold scaling is normally not dominated by atomic physics processes. Energy losses due to ELMs are examined. Different types of ELMs can be obtained, depending on plasma edge temperature and magnetics configuration. An interesting regime is the type II ELMy H-mode for configurations near double null, where the peak heat flux to the target is much reduced compared to large type I ELMs. High-resolution Thomson scattering measurements show that the edge transport barrier width in ASDEX Upgrade shows only weak variations, while the pedestal top electron pressure and pressure gradient strongly depend on the plasma current, or value of B{sub t}/q{sub 95}.
- OSTI ID:
- 20849583
- Journal Information:
- Fusion Science and Technology, Vol. 44, Issue 3; Other Information: Copyright (c) 2006 American Nuclear Society (ANS), United States, All rights reserved. http://epubs.ans.org/; Country of input: International Atomic Energy Agency (IAEA); ISSN 1536-1055
- Country of Publication:
- United States
- Language:
- English
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