Journal of Plasma and Fusion Research
Print ISSN : 0918-7928
Contributed Paper
Pedestal Characteristics of H-Mode Plasmas in JT-60U and ASDEX Upgrade
Hajime URANOYutaka KAMADATomonori TAKIZUKAWolfgang SUTTROPLorne HORTONPeter LANGHirotaka KUBONaoyuki OYAMAHidenobu TAKENAGANobuyuki ASAKURA
Author information
JOURNALS FREE ACCESS

2005 Volume 81 Issue 4 Pages 280-287

Details
Abstract

The role of the pedestal structure in ELMy H-mode plasmas for the core energy confinement and for the ELM energy losses were investigated in two tokamak-type devices, JT-60U and ASDEX Upgrade. The confinement degradation seen at higher densities is attributed to the reduction of the pedestal temperature limited by the ELM activities and the stiffness of the temperature profiles. In high triangularity or impurity seeded H-modes, in which higher energy confinement is generally achieved, a higher pedestal temperature is obtained by improving the edge MHD stability or the density profile peaking, respectively. The upper bound of the ELM energy loss is characterized by the pedestal energy. The ELM energy loss can become smaller at fixed pedestal energy when the pedestal collisionality is raised. Raising the pedestal collisionality also enhances the inter-ELM perpendicular transport loss and reduces the ELM loss power fraction. In ASDEX Upgrade, the continuous pellet injection is shown to effectively mitigate ELM losses while preserving the core confinement quality. In JT-60U, the operation regime of grassy ELM is investigated and shown to achieve highly integrated performance of high energy confinement with small ELMs in the low collisionality regime.

Information related to the author
© 2005 by The Japan Society of Plasma Science and Nuclear Fusion Research
Previous article Next article
feedback
Top