Numerical Computation of Wave-Plasma Interactions in Multi-dimensional Systems

1. Numerical Computation of Wave-Plasma Interactions in Multi-dimensional Systems D.B. Batchelor, L.A. Berry, M.D. Carter, E.F. Jaeger, E. D’Azevedo, L. Gray, T. Kaplan C.K. Phillips, R. Dumont R.W. Harvey D.N. Smithe Lodestar Research Corporation D.A. D’Ippolito, J. Myra P.T. Bonoli J.C. Wright Visit our web site at http://www.ornl.gov/fed/scidacrf

2. Goal • Obtain quantitatively accurate, predictive understanding of electromagnetic wave processes that support important heating, current drive, and stability and transport applications in fusion-relevant plasmas In non-uniform plasmamodes can couple TeraScale Supercomputers are providing access to new plasma wave physics

3. Massively - Parallel Computers Provide Access to New Plasma Wave Physics • Higher dimensionality - Computation of important wave features in 2-D and 3-D • Higher resolution - Power to resolve short wavelength structures arising from mode conversion, high dielectric constant or multi-wave interference effects • Improved calculation of wave driven plasma currents resulting from the ability to represent arbitrary, non-maxwellian distributions; retain high cyclotron harmonics; include non-local and non-linear effects in the conductivity operator • Inclusion of the effects of non-thermal populations on wave propagation and absorption

4. Increasing Resolution Results in Proper Radial Localization of Mode Converted Wavefields Nm= 15 Nm= 511

5. Project Overview • Obtain predictive understanding of electromagnetic wave processes in fusion relevant plasmas with emphasis on four major physics areas: • Effect of plasma inhomogeneity in 2-D and 3-D on wave absorption and mode conversion processes. • Effect of non-Maxwellian (generalized) velocity space particle distributions on local wave absorption, momentum generation, and instabilities. • Application of full-wave solvers to ultra-short wavelength regimes (e.g. lower hybrid waves). • Effect of global plasma modes on wave fields produced by launching structures (antennas).

6. Computational and Mathematical Challenges QPS Compact Stellarator • High dimensionality – p.d.e. in 2D or 3D for wave fields, up to 5D for distribution function  Large numbers of unknowns 105  >106 • Complex medium • Spatially non-uniform • Anisotropic • Non-local – local plasma current is an integral operator over EM field at other locations at earlier times  Use of spectral representations • Wide range of length scales involved – l ~ L l << Llength scales can interact in localized plasma regions mode conversion  Need for adaptive (but spectral) representation • Variety of physics mechanisms for absorption • Non-linearity – waves modify plasma on slow time scale, non-linear effects on waves • Basic equations are non-symmetric and dissipative

7. Collaborative Research Supported by DOEOffice of Fusion Energy Science and Office of Advanced Scientific Computing Research are Resulting in the Achievement of Physics Goals • Implementation of 1-D, 2-D, and 3-D full-wave and Fokker Planck solvers on massively parallel platforms. • Adaptation of improved serial and parallel algorithms for evaluating macroscopic plasma responses. • Reformulating wave-plasma problems and solution methods.

8. High Resolution (Nm = 160  511) is Necessary in this Mode Conversion Problem to Get The Physics Right Algorithm enhancements and MPP allowed 103 larger problem to be solved (Nm=15511)