Research Plan

• Year 1: At the first stage, we will begin by exploring the development of turbulence and associated transport in the varying pressure gradients that develop around stationary magnetic islands. Island equilibria can be obtained both analytically [using the constant-Psi approximation] or with an toroidal MHD code. The development of turbulence will be explored with a gyrokinetic code in an annulus around the magnetic island. We will investigate the effect of turbulent transport on the profiles across the island.
• Years 2-3: We will carefully benchmark the neoclassical currents predicted by gyrokinetic code(s) in preparation for carefully exploring the development of bootstrap currents generated in the pressure profiles computed with the turbulence simulations. Comparisons will be made with analytic forms of the bootstrap current. From this current the island evolution can be deduced. In a second stage we will explore the effect of turbulence on the island propagation speed and the regulating effect of the island's velocity on the turbulence in a self-consistent manner. The results of the simulations will be compared with NTM observations on JET (in collaboration with Dr. Buttery) and DIII-D (in collaboration with Dr. La Haye) and the results of scattering experiments during NTM growth on DIII-D (in collaboration with Dr. Peebles). Basic questions such as whether enhanced fluctuations develop in the vicinity of the magnetic islands during the growth of the NTM will be addressed in a joint experimental/computational effort.
• Years 3-4: We will begin to implement projective integration of the gyrokinetic represetation to evolve the magnetic island with self-consistent turbulence and bootstrap currents. The layer solutions will be matched to external solutions (e.g., Delta prime) calculated by DCON. Later BATS-R-US will be used to initialize finite size islands to initialize turbulent simulations. Calculated growth rates and critical island widths will be compared with DIII-D and JET.
• Year 5:The multiscale approach will be fully implemented to study the island evolution, including growth, saturation and propagation. The evolution will be compared with data. A survey of NTM's in ITER will be undertaken.

Key personnel and their roles

Steve Cowley and Frank Waelbroeck will share the leadership role on the NTM as organizers of the effort.

• Analytic Team: Tom Antonsen, Howard Wilson (Culham), Cowley and Waelbroeck will play the central role in developing the analytic understanding of the phenomena based on a synthesis of the results of experiment and simulation.
• Experimental Team: Comparisons of computed stability and critical island width with experiments will be led by Buttery (JET) and La Haye (GA). Tony Peebles will investigate turbulence around islands in DIII-D.
• Computational Team: The Michigan group (led by Tamas Gombosi) will generate magnetic islands that will be used as input for the gyrokinetic turbulence calculations. Ron Waltz will take the lead on the exploration of turbulence and self-consistent bootstrap current around these islands using GYRO. Alan Glasser will provide the expertise in coupling to Resistive DCON. Jean-Noel Leboeuf will help develop the annulus codes and comparisons with FAR. In parallel with these activities, Kevrekidis, Gear and Dorland will develop a coarse-grained, projective integration algorithm for island evolution using GS2 as the fundamental timestepping kernel of the kinetic physics.