Twofluid physics and fieldreversed configurations
Abstract
In this paper, algorithms for the solution of twofluid plasma equations are presented and applied to the study of fieldreversed configurations (FRCs). The twofluid model is more general than the often used magnetohydrodynamic (MHD) model. The model takes into account electron inertia, charge separation, and the full electromagnetic field equations, and it allows for separate electron and ion motion. The algorithm presented is the highresolution wave propagation scheme. The wave propagation method is based on solutions to the Riemann problem at cell interfaces. Operator splitting is used to incorporate the Lorentz and electromagnetic source terms. The algorithms are benchmarked against the Geospace Environmental Modeling Reconnection Challenge problem. Equilibrium of FRC is studied. It is shown that starting from a MHD equilibrium produces a relaxed twofluid equilibrium with strong flows at the FRC edges due to diamagnetic drift. The azimuthal electron flow causes lowerhybrid drift instabilities (LHDI), which can be captured if the ion gyroradius is well resolved. The LHDI is known to be a possible source of anomalous resistivity in many plasma configurations. LHDI simulations are performed in slab geometries and are compared to recent experimental results.
 Authors:
 TechX Corporation, 5621 Arapahoe Avenue  Suite A, Boulder, Colorado 80303 (United States)
 (United States)
 Publication Date:
 OSTI Identifier:
 20975039
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2742570; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALGORITHMS; DRIFT INSTABILITY; ELECTRONS; FIELDREVERSED THETA PINCH DEVICES; LOWER HYBRID CURRENT DRIVE; LOWER HYBRID HEATING; MAGNETOHYDRODYNAMICS; MHD EQUILIBRIUM; PLASMA; PLASMA DIAMAGNETISM; PLASMA FLUID EQUATIONS; PLASMA SIMULATION; REVERSEFIELD PINCH; REVERSEDFIELD PINCH DEVICES
Citation Formats
Hakim, A., Shumlak, U., and Aerospace and Energetics Research Program, University of Washington, Seattle, Washington 981952600. Twofluid physics and fieldreversed configurations. United States: N. p., 2007.
Web. doi:10.1063/1.2742570.
Hakim, A., Shumlak, U., & Aerospace and Energetics Research Program, University of Washington, Seattle, Washington 981952600. Twofluid physics and fieldreversed configurations. United States. doi:10.1063/1.2742570.
Hakim, A., Shumlak, U., and Aerospace and Energetics Research Program, University of Washington, Seattle, Washington 981952600. Tue .
"Twofluid physics and fieldreversed configurations". United States.
doi:10.1063/1.2742570.
@article{osti_20975039,
title = {Twofluid physics and fieldreversed configurations},
author = {Hakim, A. and Shumlak, U. and Aerospace and Energetics Research Program, University of Washington, Seattle, Washington 981952600},
abstractNote = {In this paper, algorithms for the solution of twofluid plasma equations are presented and applied to the study of fieldreversed configurations (FRCs). The twofluid model is more general than the often used magnetohydrodynamic (MHD) model. The model takes into account electron inertia, charge separation, and the full electromagnetic field equations, and it allows for separate electron and ion motion. The algorithm presented is the highresolution wave propagation scheme. The wave propagation method is based on solutions to the Riemann problem at cell interfaces. Operator splitting is used to incorporate the Lorentz and electromagnetic source terms. The algorithms are benchmarked against the Geospace Environmental Modeling Reconnection Challenge problem. Equilibrium of FRC is studied. It is shown that starting from a MHD equilibrium produces a relaxed twofluid equilibrium with strong flows at the FRC edges due to diamagnetic drift. The azimuthal electron flow causes lowerhybrid drift instabilities (LHDI), which can be captured if the ion gyroradius is well resolved. The LHDI is known to be a possible source of anomalous resistivity in many plasma configurations. LHDI simulations are performed in slab geometries and are compared to recent experimental results.},
doi = {10.1063/1.2742570},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}

After extensive experimentation on the Translation, Confinement, and Sustainment rotating magneticfield (RMF)driven field reversed configuration (FRC) device [A. L. Hoffman et al., Fusion Sci. Technol. 41, 92 (2002)], the principal physics of RMF formation and sustainment of standard prolate FRCs inside a flux conserver is reasonably well understood. If the RMF magnitude B{sub {omega}} at a given frequency {omega} is high enough compared to other experimental parameters, it will drive the outer electrons of a plasma column into near synchronous rotation, allowing the RMF to penetrate into the plasma. If the resultant azimuthal current is strong enough to reverse anmore »

Nonlinear electron magnetohydrodynamics physics. I. Whistler spheromaks, mirrors, and field reversed configurations
The nonlinear interactions of timevarying magnetic fields with plasmas is investigated in the regime of electron magnetohydrodynamics. Simple magnetic field geometries are excited in a large laboratory plasma with a loop antenna driven with large oscillatory currents. When the axial loop field opposes the ambient field, the net field can be reversed to create a fieldreversed configuration (FRC). In the opposite polarity, a strong field enhancement is produced. The timevarying antenna field excites whistler modes with wave magnetic fields exceeding the ambient magnetic field. The resulting magnetic field topologies have been measured. As the magnetic topology is changed from FRCmore » 
Twodimensional equilibria of fieldreversed configurations in a perfectly conducting cylindrical shell
Twodimensional fieldreversed equilibria bounded by a conducting cylinder are computed. The computation is made possible by using a global constraint and by using a computational algorithm that is protective of the initial guess. A pressure profile is used that has sufficient generality to match experimentally produced configurations. It is found that for some choices of separatrix radius and separatrix beta, no equilibria exist. The reasons for loss of equilibrium are discussed and an example of a configuration near loss of equilibrium conditions is given. 
Twodimensional interpreter for fieldreversed configurations
An interpretive method is developed for extracting details of the fully twodimensional (2D) “internal” structure of fieldreversed configurations (FRC) from common diagnostics. The challenge is that only external and “gross” diagnostics are routinely available in FRC experiments. Inferring such critical quantities as the poloidal flux and the particle inventory has commonly relied on a theoretical construct based on a quasionedimensional approximation. Such inferences sometimes differ markedly from the more accurate, fully 2D reconstructions of equilibria. An interpreter based on a fully 2D reconstruction is needed to enable realistic withintheshot tracking of evolving equilibrium properties. Presented here is a flexible equilibriummore » 
Analytic, two fluid, field reversed configuration equilibrium with sheared rotation
A two fluid model is used to derive an analytical equilibrium for elongated field reversed configurations containing shear in both the electron and ion velocity profiles. Like some semiempirical models used previously, the analytical expressions obtained provide a satisfactory fit to the experimental results for all radii with a few key parameters. The present results reduce to the rigid rotor model and the infinite conductivity case for a specific choice of the parameters.