Hi! Welcome to the Laboratory for Basic Plasma Physics Research here at USD! Below you will find links to descriptions of the plasma state of matter (the hottest state in the universe :) and to readings and resources that will help you see what's going on our lab.

My current research interests are these: basic plasma physics, low temperature plasma physics, the physics of sheath formation, ion dynamics in the plasma boundary layer, plasma diagnostics, laser-induced fluorescence, and the use of tunable diode lasers for ion dynamics diagnostics. My research work has been supported by the National Science Foundation and the US Dept. of Energy from 1997-2001, and from 2003 to the present. I have an ongoing collaboration with the Hershkowitz Plasma Physics research group at the University of Wisconsin-Madison, in the College of Engineering, department of Engineering Physics (where I am an Honorary Research Fellow). I also do work in area of the design of lower division and upper division physics laboratory experiments, and in the exploration of relationships between Science and Faith.

I became fascinated with the plasma state of matter during a visit to the Plasma Physics Laboratory at UCLA (Prof. Al Wong, Director) where I was an undergraduate. I eventually worked for Walter Gekelman, and Guy Dimonte while I was there (and for Mell Plummer and Onnik!. Manuel Urrutia was a good friend and compatriot during our student days---he now is an outstanding research scientist there). One day I looked inside a vacuum chamber in which a plasma was confined. It was both luminous and transparent, and just, just....awesome! I was able to see right through it, but also I could see the glow emitted from every cubic centimeter of the plasma -- an amazing sight (really, you have to take a look). That such a state of matter could one day, perhaps, become the medium in which sustained and controlled fusion reactions could occur that might be used to create enormous amounts of clean power without a negative impact on global warming (no one was talking about that in the 70's) was also very fascinating. After a Ph.D in plasma physics, and a transition to the world of the liberal arts undergraduate university, with small departments and smaller budgets (but with great opportunities to teach and to get to mentor very bright, curious, undergraduate students!), I was amazed to find that there are some very cool, very fundamental problems in basic plasma physics still unsolved, after all this time! I am working on one of those problems: the formation of the plasma sheath. It is a very cool problem. More on this presently!

• General safety guidelines
• Research student safety training form (required for getting key access to the lab)

How to build a Langmuir Probe

Plasma physics readings

• So, what is plasma?
• 80th anniversary of the creation of the field of plasma physics
• Introduction to Fusion energy and plasma
• The International Thermonuclear Experimental Reactor (ITER)
• The US ITER website
• introduction to gas discharges
• A short course on plasma physics (2012), from the National Undergraduate (Fusion) Fellowship, Princeton Plasma Physics Laboratory; of particular interest is the introduction to plasma physics, and the experimental methods lectures
• Ion Acoustic Waves
• Cool intro to the basics of vacuum systems.
• sketch of Langmuir Probe experiment
• Langmuir probes

Research journal articles

• An introduction to the problem of sheath formation, and the Bohm Criterion
• How to use diode lasers as a diagnostic (via laser-induced fluorescence, LIF) for plasma ion motion (Ar+)
• How to use diode lasers as an LIF diagnostic for plasma ion motion (Xe+)
• Bohm's criterion and sheath formation for two-ion species plasmas--this result was a surprise to the plasma physics community and began a new research journey for me. This work was done while I was on sabbatical, visiting Noah Hershkowitz in 2001. A number of papers followed, for example...
• the first direct test of the Bohm Criterion for a two-ion species plasma (Ar+, Xe+), both ions diagnosed via LIF, and
• the first direct experimental test of an new theory of sheath formation in general (multiple-ion species) plasmas. The kinetic theory of Dr. Scott Baalrud, and our work too, has attracted both interest and controversy!

Recent conference papers and posters

• Experimental Studies of Kr+ with Laser-Induced Fluorescence, G.D. Severn, T. Welsh, and Noah Hershkowitz, Poster presented at the 65th Annual Gaseous Electronics Conference, 21-26 October 2012, Austin, TX
• What’s missing from the traditional explanation of NMR experiments? G.D. Severn, J.P. Bolender (Professor of Chemistry, USD), 2012 ALPha Conference on Laboratory Instruction Beyond the First Year of College, University of Pennsylvania and Drexel University, Wednesday, July 25 - Friday, July 27, 2012
• Will a magnet fall freely in a superconducting tube? G.D. Severn, T. Welsh, 2012 ALPha Conference on Laboratory Instruction Beyond the First Year of College, University of Pennsylvania and Drexel University, Wednesday, July 25 - Friday, July 27, 2012

CV 2012