The question of how to proceed toward ever more realistic plasma simulation studies using ever increasing computing power is addressed. The answer presented here is the M3D ͑Multilevel 3D͒ project, which has developed a code package with a hierarchy of physics levels that resolve increasingly complete subsets of phase-spaces and are thus increasingly more realistic. The rationale for the multilevel physics models is given. Each physics level is described and examples of its application are given. The existing physics levels are fluid models ͑3D configuration space͒, namely magnetohydrodynamic ͑MHD͒ and two-fluids; and hybrid models, namely gyrokinetic-energetic-particle/MHD ͑5D energetic particle phase-space͒, gyrokinetic-particle-ion/ fluid-electron ͑5D ion phase-space͒, and full-kinetic-particle-ion/fluid-electron level ͑6D ion phase-space͒. Resolving electron phase-space ͑5D or 6D͒ remains a future project.Phase-space-fluid models are not used in favor of ␦ f particle models. A practical and accurate nonlinear fluid closure for noncollisional plasmas seems not likely in the near future.

Global hybrid simulations of energetic particle effects on the n=1 internal kink mode have been carried out for tokamaks. For the Internationa Thermonuclear Experimental Reactor (ITER) [ITER Physics Basis Editors et al, Nucl. Fusion 39, 2137.], it is shown that alpha particle effects are stabilizing for the internal kink mode. However, the elongation of ITER reduces the stabilization effects significantly. Nonlinear simulations of the precessional drift fishbone instability for circular tokamak plasmas show that the mode saturates due to flattening of the particle distribution function near the resonance region. The mode frequency chirps down rapidly as the flattening region expands radially outward. Fluid nonlinearity reduces the saturation level.

A three-dimensional (3-D) hybrid gyrokinetic-MHD (magnetohydrodynamic) simulation scheme is presented. To the 3-D toroidal MHD code, MH3D-K the energetic particle component is added as gyrokinetic particles. The resulting code, mh3d-k, is used to study the nonlinear behavior of energetic particle effects in tokamaks, such as the energetic particle stabilization of sawteeth, fishbone oscillations, and alpha-particle-driven toroidal Alfvén eigenmode (TAE) modes.

This paper describes the updates to and analysis of the International Tokamak Physics Activity (ITPA) Global H-Mode Confinement Database version 3 (DB3) over the period 1994-2004. Data have now been collected from 18 machines of different sizes and shapes: ASDEX, ASDEX