ITPA Transport and Confinement Topical Group

Scope

The overall scope of the Transport and Confinement Topical Group is to explore and to develop a fundamental understanding of transport and confinement physics governing plasma performance, including that of ITER and burning plasmas in general. This scope includes: maintaining the confinement and L-H threshold databases, and augmenting them as necessary; developing an understanding of the basic processes controlling plasma particle, energy and momentum transport; supporting the identification of experiments, inter-machine comparisons and analysis to address critical transport issues; and facilitating the validation of physics-based ion and electron thermal transport models in support of developing a fully predictive transport capability that could be used for integrated scenario modelling. The group will interface as necessary with other Topical Groups on cross-cutting topics.

Tasks

The tasks of the Transport and Confinement Topical Group are broad-based, covering experiment, theory and modelling. The group will work not only on characterizing transport and confinement properties, but also towards developing physics-based models with the aim of using these models to predict performance in future devices. Topics in which the group will be active will depend on both the immediate needs of ITER and the interests of the group. The high-priority topical areas of interest, and possible specific topics for focused research, are:

• Maintain confinement databases and augment these as necessary:
  • L-mode, H-mode, L-H and profile databases
• Develop an improved characterization of the L-H transition threshold:
  • Species, toroidal field, density (including low density limits)
  • Effect of rotation on threshold power
  • Confinement enhancement just above threshold
• Determine global confinement characteristics:
  • Effect of shape and edge stability on beta scaling of confinement
  • Confinement dependences in hybrid discharges
  • Effects of metal walls on confinement and transport
  • Impact of ELM control on core plasma performance, including plasma and impurity transport, rotation, etc.
  • Impact of Resonant Magnetic Perturbations (RMPs)—as a proxy for global magnetic field ripple—on confinement, local transport and rotation
• Develop an improved characterization of particle and impurity transport:
  • Parametric dependences of density peaking over a wide range of conditions, including pellet injection
  • Local particle transport and pinch processes
  • Correlations between impurity and main ion density profiles
  • Impurity transport to address burn control issues
• Determine electron thermal transport properties over a range of conditions:
  • Resolve role and importance of Electron Temperature Gradient (ETG) vs. coupled Ion Temperature Gradient (ITG)/Trapped Electron Mode (TEM)/ETG induced transport
  • Assess role of electromagnetic fluctuations in driving electron transport (low- and high-frequency)
  • Demonstrate and understand, through modelling and theory, the reduced electron transport regimes with dominant electron heating
• Determine ion thermal transport properties over a range of conditions:
  • Understand the source of ion transport under various conditions, including regimes in which neoclassical transport dominates
  • Assess the role of rotation in suppression of low-k turbulence
  • Increase test/model validity to plasmas with ITBs and other enhanced confinement regimes
• Improve characterization and understanding of momentum transport and plasma rotation:
  • Evaluate effects of rotation sources, especially with regard to intrinsic rotation
  • Determine momentum pinch velocity and its theoretical basis
  • Assess and understand effects of rotation on transport barrier formation
• Improve characterization and understanding of barrier formation:
  • Assess rates of internal and edge barrier formation in support of ITER control system development (e.g., time scales)
  • Develop understanding of triggering mechanisms (e.g. rotation vs. q-shear)
• Validate models:
  • Assess validity of physics-based transport models for basic understanding and in support of ITER scenarios
  • Incorporate turbulence measurements for comparison with synthetic diagnostics