ITPA Energetic Particle Physics Topical Group

Scope

The general scope of the ITPA Energetic Particle Physics Topical Group is to tackle the qualitatively new physics element of ITER: dominant alpha particle heating. The group shall provide the experimental basis and the theoretical knowledge to give recommendation for both the conventional and advanced scenarios in ITER in the areas of: energetic particle driven instabilities (Alfvén waves and energetic particle modes) and their consequences for plasma heating and the first wall material; effects of non-axisymmetric magnetic fields such as field ripple, error/perturbation fields; interaction of fast ions with background magnetohydrodynamic (MHD) behaviour; neutral beam injection heating and current drive; and runaway electrons. These activities will be coordinated with other Topical Groups where interests overlap. ITER itself will not mark the last stage in the development of fusion heating, and a comprehensive ab initio understanding of fast particle effects on this device will be a necessary prerequisite for bridging the gap to DEMO. The group shall therefore coordinate collaborative research activities in existing experimental devices, but in particular also encourage a close collaboration between theory and experiment. In addition, the group shall identify the diagnostic requirements for ITER, needed to extrapolate towards reactor-relevant conditions (Q > 50). Publications and presentations on the activities of the group to fusion journals and international conferences will be promoted.

Tasks

The Energetic Particle Physics Topical Group, on the basis of experimental and theoretical studies, shall provide input in the field of the following main subjects:

• Destabilization of Alfvén waves and Energetic Particle Modes (EPMs):
  • Measurements of damping rates of Alfvén waves (together with reliable mode identification: eigenfunction, frequency, etc.) and comparison with theory
  • Investigation of the drive of different kinds of Alfvén waves (toroidal, beta-induced, reversed shear, ...) and EPMs depending on the fast ion distribution function (energy and pitch angle)
  • Measurements of the influence of fast-particle-driven instabilities on the fast ion distribution function, expulsion of fast ions, comparison between experiments and state of the art non-linear theory/codes
  • Definition of benchmark test cases for fast particle stability codes
  • Development of relevant diagnostics, recommendations for ITER diagnostics
  • Prediction of the role of fast-particle-driven modes in ITER conventional and steady-state scenarios, including the power load on the first wall caused by the fast particle loss and recommendations for operation
• Effect of non-axisymmetric magnetic fields:
  • Comparison between theoretical predictions and measurements of fast ion losses caused by magnetic field ripple and error fields in present devices
  • Prediction of the power loads to the first ITER wall caused by error fields, ferritic inserts, test blanket modules and perturbation fields, i.e., by Edge Localized Mode (ELM) mitigation coils
• Interaction of fast ions with background MHD:
  • Investigation of the interaction between background MHD activity and fast particle confinement in present day devices and comparison with theory
  • Prediction of the influence of neoclassical tearing modes (NTMs) and possible synergistic effects with field ripple/error fields on fast particle confinement in ITER
  • Influence of fast ions on sawtooth stability, development of control tools for ITER
• Neutral Beam Injection (NBI) heating and current drive:
  • Investigation of the localization of NBI heating and current drive
  • Prediction of the role of NBI current drive on current profile control in ITER