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The goal of plasma science is to understand the behavior of ionized gases using an interdisciplinary approach and new techniques of analysis. Modern plasma science deals with the challenging problems associated with nonlinear, many-body phenomena in systems far from equilibrium.
Progress in plasma physics depends essentially on the close interplay between theory and experiment. Basic experiments are of central importance in the advancement of plasma science. They must be designed to isolate a particular phenomenon and to explore a broad range of plasma parameters. Theoretical and computational plasma physics complement the experimental observation.
The development of sources of quiescent (Q-machine) plasmas in the 60's made possible the first careful experimental verifications of plasma theory. Quiescent plasmas are still widely used for basic plasma research in the laboratory.
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Quiescent plasmas are cold and weakly ionized. Multipolar cusp confinement by permanent magnets reduces wall losses and increases the density of these glow discharge plasmas. |
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Picture of the quiescent plasma machine in the Associated Plasma Laboratory at INPE. In 1989 this machine replaced the smaller double plasma device which was the first experimental facility of the Laboratory back in 1979. |
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Picture of Argon plasma in the interior of the quiescent plasma machine at LAP. The glow results from excitation of the atoms by the plasma electrons. Permanent magnets surround the internal wall of the vacuum chamber, producing a multipolar cusp confining magnetic field. It is clearly seen that high-energy electrons follow the magnetic field lines of force. The thin dark object in the middle of the plasma is an electrostatic probe. |
Some of the research themes central to plasma science are: 1) wave-particle interactions and plasma heating, 2) nonlinear dynamics, chaos, turbulence and transport, 3) plasma sheaths and boundary layers, 4) magnetic reconnection and dynamo action, 5) non-neutral plasmas and strongly correlated systems.
Within this broad range of research subjects the quiescent plasma machines are particularly appropriate to explore the physics of the first three of them. The experiments already carried out in the quiescent plasma machines of the Associated Plasma Laboratory concerned basic topics such as:
1) propagation and damping of Langmuir and ion-acoustic waves in plasmas of many species,
2) plasma sheath expansion phenomena; formation and propagation of ion-acoustic solitary waves,
3) formation and properties of solitons in plasmas with negative ions,
4) ion-acoustic turbulence and double-layer formation,
5) beam-plasma interaction and Langmuir wave turbulence.
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Among the several methods available in computational physics, the Laboratory uses particle simulations to study nonlinear plasma phenomena. The figure shows the time evolution in phase space of the classic beam-plasma interaction in a bounded system. |
Who is conducting this research?
The Plasma Physics Group of the Institute of Physics of the Federal University of Rio Grande do Sul (http://www.if.ufrgs.br) is mainly concerned with research on theoretical problems in plasma science. The topics of research include interaction of waves with astrophysical and thermonuclear plasmas, nonlinear dynamics, chaos and turbulence. These topics are studied as well in the Physics Department of the Federal University of Paraná (http://www.fisica.ufpr.br).
Among the many activities of the Plasma Laboratory of the Institute of Physics of the University of São Paulo (http://www.if.usp.br) there is a line of research on chaos and turbulence.
The Institute of Physics of the Fluminense Federal University (http://www.if.uff.br) carries out theoretical research on nonlinear phenomena in plasma physics, instability and transport, and free-electron lasers.
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