The EPED pedestal model and edge localized mode-suppressed regimes: Studies of quiescent H-mode and development of a model for edge localized mode suppression via resonant magnetic perturbations

The EPED model predicts the H-mode pedestal height and width based upon two fundamental and calculable constraints: (1) onset of non-local peeling-ballooning modes at low to intermediate mode number, (2) onset of nearly local kinetic ballooning modes at high mode number. We present detailed tests of the EPED model in discharges with edge localized modes (ELMs), employing new high resolution measurements, and finding good quantitative agreement across a range of parameters. The EPED model is then applied for the first time to quiescent H-mode (QH), finding a similar level of agreement between predicted and observed pedestal height and width, and suggesting that the model can be used to predict the critical density for QH-mode operation. Finally, the model is applied toward understanding the suppression of ELMs with 3D resonant magnetic perturbations (RMP). Combining EPED with plasma response physics, a new working model for RMP ELM suppression is developed. We propose that ELMs are suppressed when a “wall”...

[1]  Frank Jenko,et al.  Nonlinear electromagnetic gyrokinetic simulations of tokamak plasmas , 2001 .

[2]  F. Waelbroeck.  Theory and observations of magnetic islands , 2009 .

[3]  M. Sugihara,et al.  Characteristics of type I ELM energy and particle losses in existing devices and their extrapolation to ITER , 2003 .

[4]  E. Doyle,et al.  ELM suppression in low edge collisionality H-mode discharges using n = 3 magnetic perturbations , 2005 .

[5]  T. Osborne,et al.  Progress towards a predictive model for pedestal height in DIII-D , 2009 .

[6]  Jet Efda Contributors,et al.  H-mode pedestal scaling in DIII-D, ASDEX Upgrade, and JET , 2011 .

[7]  Y. Kamada,et al.  Pedestal stability comparison and ITER pedestal prediction , 2009 .

[8]  Keith H. Burrell,et al.  Edge stability and transport control with resonant magnetic perturbations in collisionless tokamak plasmas , 2006 .

[9]  J. S. deGrassie,et al.  RMP ELM suppression in DIII-D plasmas with ITER similar shapes and collisionalities , 2008 .

[10]  H. Wilson,et al.  Numerical studies of edge localized instabilities in tokamaks , 2002 .

[11]  R. E. Waltz,et al.  ITER predictions using the GYRO verified and experimentally validated trapped gyro-Landau fluid transport model , 2011 .

[12]  T. Osborne,et al.  Characterization of peeling–ballooning stability limits on the pedestal , 2004 .

[13]  W. Horton,et al.  PRESSURE GRADIENT-DRIVEN MODES IN FINITE BETA TOROIDAL PLASMAS , 1989 .

[14]  T. Osborne,et al.  Limits to the H-mode pedestal pressure gradient in DIII-D , 2010 .

[15]  C. Roach,et al.  Towards the construction of a model to describe the inter-ELM evolution of the pedestal on MAST , 2011, 1107.3109.

[16]  Impact of toroidal rotation on ELM behaviour in the H-mode on JT-60U , 2004 .

[17]  Bruce D. Scott,et al.  Computation of electromagnetic turbulence and anomalous transport mechanisms in tokamak plasmas , 2003 .

[18]  G. Hammett,et al.  Electromagnetic effects on plasma microturbulence and transport , 2001 .

[19]  H. Koslowski,et al.  MHD stability analysis of small ELM regimes in JET , 2009 .

[20]  N. Ferraro.  Calculations of two-fluid linear response to non-axisymmetric fields in tokamaksa) , 2012 .

[21]  L. L. Lao,et al.  ELMs and constraints on the H-mode pedestal: peeling–ballooning stability calculation and comparison with experiment , 2004 .

[22]  H. R. Wilson,et al.  Magneto-hydrodynamic stability of the H-mode transport barrier as a model for edge localized modes: an overview , 2006 .

[23]  R. L. Miller,et al.  Magnetohydrodynamic stability of tokamak edge plasmas , 1998 .

[24]  Maxim Umansky,et al.  Stability and dynamics of the edge pedestal in the low collisionality regime: physics mechanisms for steady-state ELM-free operation , 2007 .

[25]  T. Osborne,et al.  Edge stability of stationary ELM-suppressed regimes on DIII-D , 2008 .

[26]  J. Candy.  Beta scaling of transport in microturbulence simulations , 2005 .

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

[28]  H. R. Wilson,et al.  A first-principles predictive model of the pedestal height and width: development, testing and ITER optimization with the EPED model , 2011 .

[29]  R. J. Groebner,et al.  Development and validation of a predictive model for the pedestal height , 2008 .

[30]  T. Osborne,et al.  Quiescent H-mode plasmas with strong edge rotation in the cocurrent direction. , 2009, Physical Review Letters.

[31]  M E Fenstermacher,et al.  Suppression of large edge-localized modes in high-confinement DIII-D plasmas with a stochastic magnetic boundary. , 2004, Physical review letters.

[32]  Peter Lang,et al.  Studies of the ‘Quiescent H-mode’ regime in ASDEX Upgrade and JET , 2005 .

[33]  G. Huysmans.  ELMs: MHD instabilities at the transport barrier , 2005 .

[34]  L. L. Lao,et al.  Quiescent H-mode plasmas in the DIII-D tokamak , 2002 .

[35]  G. Rewoldt,et al.  Collisional effects on kinetic electromagnetic modes and associated quasilinear transport , 1987 .

[36]  K. Burrell,et al.  Advances towards QH-mode viability for ELM-stable operation in ITER , 2011 .