Understanding of the H-mode Pedestal Characteristics using the Multi-machine Pedestal Database
T. Hatae1), M. Sugihara2), A. Hubbard3), Y. Igitkhanov2), Y. Kamada1), G. Janeschitz2), L. Horton4), N. Ohyabu5), T. Osborne6), M. Osipenko7), W. Suttrop4), H. Urano8), H. Weisen9)
1) Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki 311-0193, Japan
2) ITER Joint Central Team, Garching, Germany
3) MIT Plasma Science and Fusion Center, Cambridge, MA,USA
4) Max Planck Institut fur Plasmaphysik, Garching, Germany
5) National Institute for Fusion Science, Gifu-ken, Japan
6) General Atomics, San Diego, USA
7) Kurchatov Institute, Moscow, Russia
8) Hokkaido University, Hokkaido, Japan
9) Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, Switzerland
Abstract.
With use of a multi-machine pedestal database, essential issues for each regime of ELM Types are investigated. They include (i) understanding and prediction of pedestal pressure during Type I ELMs which is a reference operation mode of a future tokamak reactor, (ii) identification of the operation regime of Type II ELMs which have small ELM amplitude with good confinement characteristics, (iii) identification of upper stability boundary of Type III ELMs for the access to the higher confinement regimes with Type I or II ELMs, (iv) relation between core confinement and pedestal temperature in conjunction with the confinement degradation in high density discharges. Scaling and model based approaches for expressing pedestal pressure are shown to roughly scale the experimental data similarly well and initial predictions for the future reactor case could be performed by them. It is identified that q and d are important parameters to obtain the Type II ELM regime. A theoretical model on Type III ELMs is shown to reproduce the upper stability boundary reasonably well. It is shown that there exists some critical pedestal temperature, below which the core confinement starts to degrade. It is also shown that improved pedestal conditions for good confinement in high density discharges is possible by increasing the plasma triangularity.