LETTER TO THE EDITOR: Scaling of H-mode edge pedestal pressure for a Type-I ELM regime in tokamaks

Scaling of H-mode edge pedestal pressure for a Type-I ELM regime based on a simple analytical formula (Hatae T et al 2001 Nucl. Fusion 41 285) can be significantly improved by introducing shaping factors into the scaling, which is motivated by a recent development of the MHD model for the critical pressure gradient (Snyder P B et al 2002 Phys. Plasmas 5 2037, Lao L L et al 2002 ITPA H-mode Edge Pedestal Physics Topical Group Meeting (San Diego)). The physics basis of these shaping factors is an enhancement of the critical pressure gradient determined by a high toroidal mode number, n, ideal ballooning mode through the effect of the magnetic well. On an increase in the magnetic well, peeling and ballooning modes decouple and the critical gradient is determined by the intermediate n mode, which enhances the critical gradient substantially. The improved scaling can reproduce the pedestal pressure reasonably well for ASDEX-U, JET and JT-60U Type-I ELMy data archived in the International Pedestal Database version 3.

[1]  Tomonori Takizuka,et al.  Pedestal characteristics and extended high-βp ELMy H-mode regime in JT-60U , 2002 .

[2]  Y. Wang,et al.  H mode confinement in Alcator C-Mod , 1997 .

[3]  Hiroshi Shirai,et al.  Edge-core relationship of ELMy H-mode plasmas in JT-60U , 2002 .

[4]  M. J. Mantsinen,et al.  The edge operational space in JET , 1999 .

[5]  Jose Milovich,et al.  Toroidal gyro‐Landau fluid model turbulence simulations in a nonlinear ballooning mode representation with radial modes , 1994 .

[6]  H. Shirai,et al.  Characteristics of edge pedestal width in JT-60U ELM-free H-mode plasmas , 1998 .

[7]  J. G. Cordey,et al.  Development of a two-term model for the confinement in ELMy H-modes using the global confinement and pedestal databases , 2002 .

[8]  Tomonori Takizuka.  AN OFFSET NONLINEAR SCALING FOR ELMY H-MODE CONFINEMENT , 1998 .

[9]  L. Lao,et al.  Edge localized modes and the pedestal: A model based on coupled peeling–ballooning modes , 2002 .

[10]  R. J. Groebner,et al.  Scaling studies of the high mode pedestal , 1998 .

[11]  M. Sugihara,et al.  Understanding of H mode pedestal characteristics using the multimachine pedestal database , 2001 .

[12]  Examinations on various scalings for the H-mode edge pedestal width , 2002 .

[13]  M. V. Hellermann,et al.  Plasma-edge Gradients in L-mode and ELM-free H-mode JET Plasmas , 1998 .

[14]  L. L. Lao,et al.  Dependence of H-mode pedestal parameters on plasma magnetic geometry , 2002 .

[15]  M. Sugihara,et al.  A model for H mode pedestal width scaling using the International Pedestal Database , 2000 .

[16]  Joseph A. Snipes,et al.  Latest results on the H-mode threshold using the international H-mode threshold database , 2000 .

[17]  Frederic V. Hartemann,et al.  High-Intensity Scattering Processes of Relativistic Electrons in Vacuum and Their Relevance to High-Energy Astrophysics , 1998 .