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3D MHD simulation of Caltech plasma jet experiment: First results

Author: Xiang Zhai
Requested Type: Poster Only
Submitted: 2014-05-28 23:10:45

Co-authors: H. Li, P. Bellan, S. Li

Contact Info:
Caltech
1200 E California Blvd
Pasadena, CA   91125
USA

Abstract Text:
We present a time-dependent ideal MHD numerical simulation of the Caltech plasma jet experiment using a magnetic tower scenario as the baseline model. The simulation uses the LA-COMPUSS MHD code developed by H. Li and S. Li to solve the ideal MHD equations in a 3D Cartesian coordinate system using an 800x800x800 grid on a 512 parallel processor system. The spatial resolution of the simulation is comparable to the ion skin depth of the experimental plasma. Magnetic fields consist of an initially localized dipole-like poloidal component and a toroidal component that is continuously injected into the vicinity of the coplanar coaxial electrodes. Magnetic field energy is thereby continuously injected into the system. The injected toroidal field deforms the plasma and stretches the frozen-in poloidal field, resulting in a pressure gradient perpendicular to the electrode plane. This MHD-induced pressure gradient drives the plasma to form a collimated Alfvenic flow with frozen-in open helical magnetic field lines. The MHD-driven flow has a velocity equal to the toroidal Alfven velocity. Detailed comparison between the simulation and experiment provide a comprehensive description of the interplay among magnetic force, pressure and flow effects. In particular, we delineate both the magnetic and kinetic profiles of the flow and the transition process that converts the injected magnetic energy to kinetic energy. With suitably chosen parameters that are derived from experiments, the simulation jet reproduces the experimental jet quantitatively in terms of magnetic/kinetic energy, current, flow radius and propagation velocity. Specifically, the flow velocity in the simulation is proportional to the poloidal current divided by the square root of the plasma density, in agreement with both the experiment and analytical theory.

Characterization: 2.0,4.0

Comments:
The authors wish to have this poster next to other Caltech Bellan group posters (Chai & Bellan, Chaplin & Bellan, Haw & Bellan). Thanks.

Workshop on Exploratory Topics in Plasma and Fusion Research (EPR) and US-Japan Compact Torus (CT) Workshop
August 5-8, 2014
Madison, Wisconsin

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