Workshop Working Groups and Topics

This year, the TTF Workshop will consist of:

i.) Special Plenary Topical Contributed Sessions
ii.) Working Group Sessions
iii.) Posters

Special Plenary Topical Contributed Sessions
This year we plan to hold two special interdisciplinary plenary contributed sessions. The topics of these sessions are:

P1) Experimental characterization of the H-mode pedestal structure and transport processes, and comparison with modeling and theory (R. Maingi and T. Rognlien)

It is predicted that the core performance of ITER will dependstrongly on the temperature and pressure at the top of the H-mode pedestal. Simultaneously the ITER pedestal must reside in a strongly mitigated ELM or ELM-suppressed regime, as large heat loads are intolerable. To improve predictive capability for ITER, the US Dept. of Energy 2011 experiment and theory Joint Research Target was focused on pedestal structure, with an emphasis on comparison between data and models. New profile and fluctuations data with substantially upgraded diagnostics were obtained from the Alcator C-Mod, DIII-D, and NSTX devices, and these were the focus of simulations with a range of models. In this session, the results of this large national effort, both experiment and modeling, will be presented to and discussed with the community. We solicit abstracts for this Plenary session both from direct participants and other community members who wish to contribute.

P2) Transport in Low Torque Plasmas (J. Rice and G. Staebler)

Most of the experimental database in tokamaks comes from discharges with significant external torque from neutral beams. ITER must be able to operate at relatively low torque so it is critical to understand the impact this will have on transport. This session will focus on experiments and theory of low torque regimes in present devices of all kinds. This includes but is not limited to: intrinsic rotation, changes in transport stiffness and methods for improving confinement without large torque.  Papers that explore the changes in transport that occur due to changes in rotation/torque or that are effective in low rotation/torque discharges will be given priority.

The purpose of these sessions is to stimulate interdisciplinary discussion and interchange on themes common to the TTF as a whole, without the interference of parallel sessions. To this end, these sessions will be PLENARY. The plenary sessions will consist of brief introductory overviews, several contributed oral papers, and group discussion, with a discussion leader.

TTF meeting participants are encouraged to submit contributed papers to these two special sessions. The scope of the topics is intentionally broad, so as to accommodate a diversity of approaches. The two topics span all aspects of the TTF. Hence, novel interpretations and directions are very welcome! In the event that a submission to one of the special sessions is not selected, it can be considered for a regular working group.

Working Groups

Each working group includes both theory and experiment, with the ultimate goal being tests of theory, simulations and models against experiment. In addition, diagnostic needs and novel diagnostic ideas for a given area are also included in the scope of each working group. The reality of the ITER project provides extra impetus for work on burning plasma transport issues relevant to each of the working groups.

A. Core Transport Working Group (L. Schmitz, G. Staebler)

The core working group covers transport issues from the center of the plasma to the top of the H-mode edge pedestal. Topics include:

     • Electron and ion thermal transport
     • Particle transport
     • Momentum transport and generation of rotation
     • Profile/transport control/modification issues (e.g. role of rotation, sources plasma shape, etc.
     • Formation, control and dynamics of Internal Transport Barriers
     • Core-edge interface (the edge as a dynamic boundary for the core)
     • Physics of transport structures (e.g. zonal flows, streamers, avalanches)
     • High performance and burning plasmas (i.e. steady state, bootstrap dominated, etc.)

This years focus areas for the Core Breakout Oral Session is:

Progress on the 2012 Joint Research Target for core transport validation of theory: Preliminary work towards meeting the JRT can be presented for community input. This session will focus on the metrics and procedures that are being used for validation with the goal of developing common standards. Examples include recent results on particle and electron thermal tranpsort based on new diagnostic and/or simulation capabilities.

Transport in the core/edge transition region: It has been demonstrated that delta-f gyrokinetic simulations of turbulence in the L-mode edge fall far short of the observed level of energy transport and density fluctuations in some discharges. This session aims to examine the experimental conditions where this underprediction occurs in order to help identify the missing physics in the simulations.

 

B. Edge Physics Working Group (R. Maingi, T. Rognlien)

The Edge Physics group covers transport physics in the region just inside and outside the last closed flux surface, with emphasis on H-mode plasmas. Topics of interest include:

     • Physics of H-mode pedestal structure
     • Pedestal Transport, sources and sinks
     • Transport induced by ELMs and other edge MHD activity
     • Transport in the scrape-off layer
     • Mechanism for L-H transition, including transient regimes
     • Physics of hysteresis and the back-transition
     • Physics of the density limit

This years focus areas for the Edge Physics Breakout Oral Session are:

C. Momentum Transport and the Origins of Spontaneous Rotation (P. Diamond, J. Rice, W. Solomon)

This working group was created to increase focus on plasma rotation, which influences transport in a number of ways. Important topics for the 2012 meeting include:

     • Toroidal momentum transport, especially non-diffusive mechanism, off-diagonal
     • Cross coupling between particle transport and momentum transport
     • Influence of edge plasma properties on spontaneous rotation and momentum transport
     • Poloidal momentum transport in low collisionality plasmas
     • Integrated modeling of spontaneous rotation

 

D. Fast Particle Working Group (G.-Y. Fu, M. van Zeeland)

     • Observations and modeling of fast-particle-driven instabilities and fast particle transport
     • Assessment of fast particle effects on burning plasma performance (e.g. ITER)
     • Fast particle diagnostics and MHD spectroscopy
     • Theory and simulation of nonlinear wave-particle interactions
     • Interpretation of fast particle data from present experiments and projections for burning plasmas

The 2012 EP WG sessions will encourage interaction between theorists and experimentalists to work together with emphasis on validation issues.

 

E. 3D (C.S.Chang, T. Evans)

To clarify the role of non-axisymmetric effects in tokamaks, stellarators and RFPs through intrinsic or applied 3D magnetic structures. Magnetic perturbations have been found to have a strong influence in controlling ELMs through stochastization of the magnetic field, and also to control zonal flows.

This year's focus areas for the 3D breakout oral session are:

1) The effect of the plasma properties, such as collisionality, density, temperature, and shaping, on the 3D field formation by external perturbation

2) The relationship between changes in the mean edge radial electric field, the zonal flow, and the transport during the application of 3D fields.

3) Changes in density, temperature and potential fluctuations during the application of 3D fields.

 

F. Verification and Validation Working Group (C. Holland)

The Verification and Validation Group has been charged with examining verification and validation (V&V) as it has been defined and structured generally and in other scientific fields, and with formulating V&V procedures and practices applicable to the range of numerical modeling activities within the U.S. Fusion Program, taking into consideration the goals, expectations and desired outcomes of different modeling activities, and resource limitations that are likely to apply to verification and validation. Verification and validation were discussed at a town hall meeting in 2007 and 2008 as part of an effort to examine the state of the art of experiment/model comparison, to confront and seek solutions to particular challenges in performing validation in fusion, and to begin forging consensus about what validation in fusion should be and should accomplish. The town hall meeting was organized by a focused task group that this year seeks to broaden its base and help formulate ideas for validation campaigns involving experiment, modeling, and theory. It is hoped that these efforts will evolve into a cross-cutting working group that interacts in the other TTF working group sessions to advance validation as a common exercise in physics, and meets less frequently to handle technical issues specific to verification and validation.

The V&V group intends to solicit work that describes the development, use, and effectiveness of validation metrics. A discussion will be held on whether existing metrics are sufficient for various needs, such as having confidence in ITER predictions, and if not, to identify what changes/extensions/new metrics are needed.