Nathan Rynn

Professor Emeritus, Physics & Astronomy
School of Physical Sciences

PH.D., Stanford University, 1956
M.S., University of Illinois, 1947

Phone: (949) 824-5944
Fax: (949) 824-2174

University of California, Irvine
4162 Reines Hall
Mail Code: 4575
Irvine, CA 92697
Research Interests
Experimental plasma physics, especially fundamental phenomena such as transport, diffusion, instabilities and chaos
Academic Distinctions
:: American Association for the Advancement of Science Fellow, 1992
:: American Physical Society Fellow, 1969
:: Ecole Polytechnique de Lausanne, Switzerland, Professeur Invite
:: Ecole Polytechnique de Palaiseau, France, Professeur Invite
:: Fulbright Fellowship, 1978
:: Institute of Electrical and Electronic Engineers, Life Fellow 1980
Research Abstract
Professor Rynn earned his B.E.E. from the City College of New York, his M.S. from the University of Illinois, and his Ph.D. (1956) from Stanford University. He is a Fellow of the American Physical Society, and the American Association for the Advancement of Science, and a Life Fellow of the Institute of Electrical and Electronic Engineers. He joined the Physics Department at UCI in 1966.

In the 1950-60s the main impetus for studying plasma physics was the massive program to develop a controlled thermonuclear reaction (CTR) , now just abbreviated to "fusion". Since then, interest has expanded to include plasma processing, and there has been a reawakened interest in magnetospheric, space, and astrophysical plasma physics. The prime difficulty in the pursuit of the subject is a lack of knowledge of the fundamental processes of a plasma. The Q-Machine was developed in an effort to fill this gap. The Q-machine is a large laboratory device which generates a "quiet" plasma on which to do experiments. It uses the phenomenon of surface ionization of certain metals on hot surfaces, e.g., cesium on hot tungsten. The column is contained in a strong, longitudinal magnetic field (of the order of 4-5,000 gauss). The plasma temperature is about 2500 degrees K which is high by everyday experience but quite low by CTR standards. We ionize barium on a hot rhenium surface. Although barium is not a nice metal to work with it does have very useful optical properties. In particular, singly ionized barium--which is produced by contact ionization--has a single electron in its outer orbit and this permits its excitation by an appropriate laser beam. We have been developing optical diagnostics, called Laser Induced Fluorescence (LIF) for a long time and, by now, have refined it to the point where we can use it for the non-perturbing diagnostics of plasmas. We can measure ion velocity distributions; follow particles, experimentally, in phase space; and tag particles so that we can follow them in space, time, and velocity space. We use this powerful technique to probe the transport properties of plasmas directly, i.e. we measure, rather than infer, as much as possible about diffusion and other transport mechanisms. We do this in plasmas that are "quiet" and that are turbulent. This has led to some exciting insights into plasma behavior. We are continuing this program and, in addition to the investigation of transport, we are also looking at what happens to a charged particle beam when it is injected into a plasma. A second program in which we are involved is the construction of an electron-positron (positronium) plasma. This is an "equal mass" plasma with some unusual properties. The experiment is currently under way and we have already trapped a positron in a magnetic mirror. We are now working toward a higher density positronium plasma with a stronger positron source.
A Novel Extension to Laser Induced Fluorescence, (with T. Ross and D. Newsham) Rev. Sci. Instrum. 67, 3117 (1996).

Slowing Down Of An Ion Beam In A Background Plasma, (with D. Newsham and T.J. Ross) Phys. Plasmas, 3, 2824 (1996).

Direct Measurement of Velocity Space Transport in a Plasma, (with J. Bowles and R. McWilliams) Phys. Plasmas 1, 3814 (1994).
Conservation Laws and Transport in Hamiltonian Chaos (with F. Skiff, F. Anderegg, T.N. Good, P.J. Paris, M.A. Tran, R.A. Stern) Phys. Rev. Lett. 61(18), 2034, (1988).
Determination of Plasma Ion Transport Coefficients by Direct measurement of Ion Velocity Distributions, to be published in the Proceedings of the 1995 Cambridge Symposium/ Workshop, February 20-25, 1995, Bermuda, Tom Chang, Editor.
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