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The stability of a plasma is an important consideration in the study of plasma physics. When a system containing a plasma is at equilibrium, it is possible for certain parts of the plasma to be disturbed by small perturbative forces acting on it. The stability of the system determines if the perturbations will grow, oscillate, or be damped out.
A reversed-field pinch (RFP) is a device used to produce and contain near-thermonuclear plasmas. It is a toroidal pinch which uses a unique magnetic field configuration as a scheme to magnetically confine a plasma, primarily to study magnetic confinement fusion. Its magnetic geometry is somewhat different from that of the more common tokamak. As one moves out radially, the portion of the magnetic field pointing toroidally reverses its direction, giving rise to the term reversed field. This configuration can be sustained with comparatively lower fields than that of a tokamak of similar power density. One of the disadvantages of this configuration is that it tends to be more susceptible to non-linear effects and turbulence. This makes it a useful system for studying non-ideal (resistive) magnetohydrodynamics. RFPs are also used in studying astrophysical plasmas, which share many common features.
Magnetic confinement fusion (MCF) is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of controlled fusion research, along with inertial confinement fusion.
A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring.
The Madison Symmetric Torus (MST) is a reversed field pinch (RFP) physics experiment with applications to both fusion energy research and astrophysical plasmas.
The Experimental Advanced Superconducting Tokamak (EAST), internal designation HT-7U, is an experimental superconducting tokamak magnetic fusion energy reactor in Hefei, China. The Hefei Institutes of Physical Science is conducting the experiment for the Chinese Academy of Sciences. It has operated since 2006.
The beta of a plasma, symbolized by β, is the ratio of the plasma pressure (p = nkBT) to the magnetic pressure (pmag = B²/2μ0). The term is commonly used in studies of the Sun and Earth's magnetic field, and in the field of fusion power designs.
The Helically Symmetric Experiment, is an experimental plasma confinement device at the University of Wisconsin–Madison, with design principles that are intended to be incorporated into a fusion reactor. The HSX is a modular coil stellarator which is a toroid-shaped pressure vessel with external electromagnets which generate a magnetic field for the purpose of containing a plasma. It began operation in 1999.
The Columbia Non-neutral Torus (CNT) is a small stellarator at the Columbia University Plasma Physics Laboratory designed by Thomas Sunn Pedersen with the aid of Wayne Reiersen and Fred Dahlgren of the Princeton Plasma Physics Laboratory to conduct the first investigation of non-neutral plasmas confined on magnetic surfaces. The experiment, which began operation in November 2004, is funded by the National Science Foundation and the United States Department of Energy in the form of a Faculty Early Career Development (CAREER) award.
In magnetic confinement fusion the zonal direction primarily connotes the poloidal direction, the corresponding coordinate being denoted by y in the slab approximation or θ in magnetic coordinates. However, in the fusion context, usage is restricted to the context of zonal plasma flows and there will in general be a toroidal component in such flows as well. Thus, although the term zonal has come into use in plasma physics to emphasize an analogy with zonal flows in geophysics, it does not uniquely identify the direction of flow, unlike the case in geophysics.
The terms toroidal and poloidal refer to directions relative to a torus of reference. They describe a three-dimensional coordinate system in which the poloidal direction follows a small circular ring around the surface, while the toroidal direction follows a large circular ring around the torus, encircling the central void.
Gyrokinetics is a theoretical framework to study plasma behavior on perpendicular spatial scales comparable to the gyroradius and frequencies much lower than the particle cyclotron frequencies. These particular scales have been experimentally shown to be appropriate for modeling plasma turbulence. The trajectory of charged particles in a magnetic field is a helix that winds around the field line. This trajectory can be decomposed into a relatively slow motion of the guiding center along the field line and a fast circular motion, called gyromotion. For most plasma behavior, this gyromotion is irrelevant. Averaging over this gyromotion reduces the equations to six dimensions rather than the seven. Because of this simplification, gyrokinetics governs the evolution of charged rings with a guiding center position, instead of gyrating charged particles.
Liu Chen is an American theoretical physicist who has made original contributions to many aspects of plasma physics. He is known for the discoveries of kinetic Alfven waves, toroidal Alfven eigenmodes, and energetic particle modes; the theories of geomagnetic pulsations, Alfven wave heating, and fishbone oscillations, and the first formulation of nonlinear gyrokinetic equations. Chen retired from University of California, Irvine (UCI) in 2012, assuming the title professor emeritus of physics and astronomy.
TJ-II is a flexible Heliac installed at Spain's National Fusion Laboratory.
The Compact Toroidal Hybrid (CTH) is an experimental device at Auburn University that uses magnetic fields to confine high-temperature plasmas. CTH is a torsatron type of stellarator with an external, continuously wound helical coil that generates the bulk of the magnetic field for containing a plasma.
Guy Laval is a French physicist, professor at the École polytechnique and member of the French Academy of Sciences.
Akira Hasegawa is a Japanese theoretical physicist and engineer who has worked in the U.S. and Japan. He is known for his work in the derivation of the Hasegawa–Mima equation, which describes fundamental plasma turbulence and the consequent generation of zonal flow that controls plasma diffusion. Hasegawa also made the discovery of optical solitons in glass fibers, a concept that is essential for high speed optical communications.
Patrick Henry Diamond is an American theoretical plasma physicist. He is currently a professor at the University of California, San Diego, and a director of the Fusion Theory Institute at the National Fusion Research Institute in Daejeon, South Korea, where the KSTAR Tokamak is operated.
The Tokamak Chauffage Alfvén Brésilien (TCABR) is a tokamak situated at the University of Sao Paulo (USP), Brazil. TCABR is the largest tokamak in the southern hemisphere and one of the magnetic-confinement devices committed to advancing scientific knowledge in fusion power.
In magnetic confinement fusion, a flux surface is a surface on which magnetic field lines lie. Since the magnetic field is divergence-free, the Poincare-Hopf theorem implies that such a surface must be either a torus, or a knot. In the tokamak and the stellarator flux surfaces have toroidal shapes, whereas the more exotic knotatron has a knotted flux surface. Flux surfaces are typically characterized by the poloidal magnetic flux or the toroidal magnetic flux. The poloidal flux is the magnetic flux passing through a ribbon going from the magnetic axis to the flux surface, and the toroidal flux is the magnetic flux passing through a circle which encloses the magnetic axis. The total flux passing through flux surface itself is zero, as magnetic field lines are everywhere tangent to the surface.
References
- Diamond, P. H.; Itoh, S.-I.; Itoh, K.; Hahm, T.S. (2005). "Zonal flows in plasma—a review" (PDF). Plasma Phys. Control. Fusion. 47 (5): R35–R161. Bibcode:2005PPCF...47R..35D. doi:10.1088/0741-3335/47/5/R01.
- Dewar, R. L.; Abdullatif, R. F. (2007). "Zonal flow generation by modulational instability". In Eds. Denier, J. P. (ed.). Frontiers in Turbulence and Coherent Structures - World Scientific Lecture Notes in Complex Systems. Proceedings of the CSIRO/COSNet Workshop on Turbulence and Coherent Structures, Canberra, Australia, 10–13 January 2006. Vol. 6. and Frederiksen, J. S. Singapore: World Scientific. pp. 415–430. arXiv: physics/0610016 . Bibcode:2007ftcs.conf..415D. doi:10.1142/9789812771025_0017. ISBN 978-981-270-393-4.
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