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Simulation of FLR effects on RFP tearing modes.

Author: Charlson C. Kim
Requested Type: Consider for Invited
Submitted: 2006-12-18 13:26:47

Co-authors:

Contact Info:
PSI Center, U. of Washington
Room 120 AERB, Box 352250
Seattle, Wa   98195-2
USA

Abstract Text:
The Plasma Science and Innovation Center (PSI Center) extends
and applies MHD codes to understand and eventually predict
emerging concept (EC) experiments. Kinetic effects such as
finite Larmour radius (FLR), Landau resonances and phase
space anisotropies are known to significantly impact the
dynamics of many EC experiments.

The PSI Center has extended the hybrid kinetic-MHD
implementation in NIMROD footnote{C.C. Kim et.al. " Hybrid
Kinetic-MHD Simulations in General Geometry", CPC {bf 164},
448 (2004)} from the drift kinetic model to the full kinetic
model to include sufficient physics to accurately account
for many of these effects, in particular FLR effects. The full
kinetic implementation uses the Boris push to advance the Lorentz
equations of motion and the $delta f$ method to compute moments
of the particle distribution function. These moments (in our
applications, the kinetic pressure tensor) are coupled to the
MHD equations evolved in NIMROD. With this technique, we
simulate the effects of an energetic minority species on the
plasma dynamics. However, satisfaction of the gyro-frequency
Courant condition may place a severe restriction on the particle
time step relative to MHD time scales. For computational
efficiency, we orbit average the kinetic contribution (the
$deltaf$ PIC) over the MHD time step.

Our first application simulates FLR effects on RFP tearing modes.
Linear analysis by Svidzinski footnote{V.~A.~Svidzinski and
S.~C.~Prager, ''Effects of particles with large gyro-radii on
resistive magnetohydrodynamic stability'', PoP {bf 11}, 980 (2004)}
has shown that FLR effects significantly reduce tearing modes in
RFPs. Comparisons of the simulation and the analytic results will
be presented. We also present recent studies that extend the
simulations beyond the regimes accessible by analytics.

Characterization: E10

Comments:
please place with PSI Center posters.