Commun. Comput. Phys.,
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Volume 4.


Full Wave Simulations of Lower Hybrid Waves in Toroidal Geometry with Non-Maxwellian Electrons

J. C. Wright 1*, E. J. Valeo 2, C. K. Phillips 2, P. T. Bonoli 1, M. Brambilla 3

1 MIT - Plasma Science Fusion Center, Cambridge, MA, USA.
2 Plasma Physics Laboratory, Princeton, NJ, USA.
3 Max Planck Institute for Plasma Physics Garching, Germany.

Received 5 December 2007; Accepted (in revised version) 6 February 2008
Available online 14 April 2008

Abstract

Analysis of the propagation of waves in the lower hybrid range of frequencies in the past has been done using ray tracing and the WKB approximation. Advances in algorithms and the availability of massively parallel computer architectures has permitted the solving of the Maxwell-Vlasov system for wave propagation directly [Wright et al., Phys. Plasmas (2004), 11, 2473-2479]. These simulations have shown that the bridging of the spectral gap (the difference between the high injected phase velocities and the slower phase velocity at which damping on electrons occurs) can be explained by the diffraction effects captured in the full wave algorithm - an effect missing in WKB based approaches. However, these full wave calculations were done with a Maxwellian electron distribution and the presence of RF power induces quasilinear velocity space diffusion that causes distortions away from an Maxwellian. With sufficient power, a flattened region or plateau is formed between the point of most efficient damping on electrons at about 2-3 $v_\mathrm{the}$ and where collisional and quasilinear diffusion balance. To address this discrepancy and better model experiment, we have implemented [Valeo et al., "Full-wave Simulations of LH wave propagation in toroidal plasma with non-Maxwellian electron distributions", 18th Topical Conference on Radio Frequency Power in Plasmas, AIP Conference Proceedings (2007)] a non-Maxwellian dielectric in our full wave solver. We will show how these effects modify the electron absorption relative to what is found for a Maxwellian distribution.

AMS subject classifications: 35Q60, 65L60, 74J05, 82D10

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Key words: Simulation, parallel, wave-equation, plasma, lowerhybrid.

*Corresponding author.
Email: jwright@psfc.mit.edu (J. C. Wright), valeo@pppl.gov (E. J. Valeo), ckphillips@pppl.gov (C. K. Phillips), bonoli@psfc.mit.edu (P. T. Bonoli), mab@ipp.mpg.de (M. Brambilla)
 

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