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Hybrid Kinetic-MHD Studies of ICC Devices using Lorentz PIC in Finite Elements

Author: Charlson C. Kim
Requested Type: Poster Only
Submitted: 2009-12-04 16:00:27

Co-authors: R.D. Milroy and the NIMROD Team

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

Abstract Text:
Progress on the implementation of a Lorentz force Particle-in-Cell (PIC) module
for the NIMROD code will be presented. This is an extension of the drift kinetic
delta-f PIC module already in place in NIMROD (C. C. Kim `` Impact of velocity
space distribution on hybrid kinetic-magnetohydrodynamic simulation of the (1,1)
mode'', Phys. Plasmas 15, 072507 (2008)). Resolution, both temporal and
spatial, of the full Lorentz orbit is necessary to capture the energetic ion
physics in ICC configurations. ICC configurations lack the strong guide field
of tokamaks and lie outside the validity regime of small Larmour radius
ordering, indeed sometimes rho/L~1 (e.g. FRC) - mu [=(mvperp2)/(2B)], the first
adiabatic invariant is grossly violated. Nonetheless, visualization of the
trajectories reveal surprising order which may shed light towards new paths of
analytic reduction. Of course the real impact of the hybrid simulations is in
the coupling of energetic particle effects with the evolving MHD plasma. Our
initial hybrid simulations will apply the CGL-like pressure tensor to couple the
energetic particles to the MHD plasma. We also present progress on coupling
through a full pressure tensor and through the current.

Particular challenges of the hybrid kinetic-MHD implementation are PIC methods
in general geometry high order finite element grid, resolving the finite Larmour
trajectory (both spatially and temporally), and coupling to the resistive time
scales of the MHD fluid variables. The initial simulation results presented
will examine the successes and shortcomings of the implementation and possible
paths to improvements

The Lorentz force PIC module will be used to study the effects of energetic ions
on stability and confinement of innovative confinement concept (ICC) devices.
FLR effects may also be important in the high energy tails of energetic particle
distributions found in tokamaks, particularly for energetic particle modes such
as TAEs. As an initial application, we use the the Lorentz PIC module as tracer
particles to study trajectories in ICC devices and the resultant phase space
distribution function. We will show visualizations of the trajectories of
energetic ions that reveal surprising geometric features analogous to closed
surface bound by the first adiabatic invariant but with more complex
morphologies. Moments of the equilibrium trajectories reveal the non-MHD
features of the ICC devices examined. We also present preliminary simulations
of kinetic FLR effects on FRCs and other ICC configurations. In particular, we
examine the impact of kinetic effect on the stability of the ICC configurations.
Comparisons with the drift kinetic model will also be presented where possible.

Characterization: E10

Comments:
please place with other PSI Center posters