The UW Plasma Physics Group Clint Sprott, Paul Terry, Ellen Zweibel, Stas Boldyrev, Dalton Schnack, Cary Forest, Stewart Prager Presented to Introductory Seminar for New Graduate Students on September 6, 2007

Plasma Physics n What is a Plasma? u Ionized gas (kT > a few eV) u The fourth state of matter u 99% of the universe n History of Plasma Physics u 1920’s - Langmuir (vacuum tubes) u 1930’s - Appleton (ionosphere) u 1950’s - Nuclear Fusion u 1960’s - Solar wind, stellar interiors u 1980’s - Industrial applications

Wisconsin Plasma Physics Program n Began in 1962 by Donald W. Kerst n Present Physics Faculty u Clint Sprott (computational dynamics) u Paul Terry (theory) u Ellen Zweibel - joint with Astronomy (theory) u Stas Boldyrev (theory) u Dalton Schnack – part-time (computational) u Cary Forest (experimental) u Stewart Prager (experimental) n Plasma Research in other UW Departments u Stellarator/Torsatron (ECE) u Spherical Tokamak (EP) u Fusion Technology Institute (EP) u Plasma Theory & Computation (EP) u Plasma Processing (EP)

Plasma Physics Group n Composition u 7 faculty u 11 scientists u 9 postdocs u 28 graduate students u 27 support staff u + frequent and long-term visitors u ==> ~ 80 people total n Funding (~$8M year) n ~80 Ph.D. graduates over 40 years u 50% at National Labs u 25% at Universities u 25% in Industry n

Nuclear Fusion n D + T  4 He (3.5 MeV) + n (14 MeV) n “Inexhaustible” Source of Energy u D 2 in oceans will last 3 x 10 8 years u 1 gal H 2 ) = 1/8 g D 2 = 300 gal gasoline n Must contain DT kT > 10 keV for n  > sec/m 3 (Coulomb barrier) n Scientific Feasibility Essentially Proven n Much Work Remains u Physics u Technology

What to do if Interested n Come around and get Acquainted n Take Plasma Courses u 525 introduction u 526 plasma lab (EP) u 527 confinement devices u 528 plasma processing u 724 waves & instabilities u 725 plasma kinetic theory u 726 magnetohydrodynamics n Plasma Seminar: 12:05 Mon (1227 Engr) n Group Meeting: 4:00 Thurs (5280 Ch) n Summer Jobs Available n Pass Qualifiers

Paul Terry

Turbulence in fusion and astrophysics Interests (organizing principles): Physics of coherent structure formation in turbulence Role of symmetry-breaking waves Role of strongly inhomogeneous background (e.g., shear flow) Applications: Transport in fusion plasmas Interstellar medium

Ellen Zweibel

Stas Boldyrev

Why to Study Plasma Physics? Almost all Galactic volume and Universe volume are filled with a plasma! Controlled fusion – practically infinite source of energy! It is just fun – astrophysical plasma flows exhibit regimes that have never been investigated in terrestrial experiments!

What is special about plasma? n Very hot, ionized gas. n How to confine it? n Plasma consists of electrons and ions weakly interacting with each other. Can sustain currents -> can interact with magnetic fields.

Plasma in Magnetic Field Good confiment Magnetized plasma is usually unstable and turbulent

Plasma Turbulence 10 –4 10 –8 10 –12 P( n ) (T 2 ) Toroidal Mode, n ~ n –3/2 ~ n –5/3 Standard Reduced-Tearing Solar wind MST, UW-Madison

Plasma Turbulence Interstellar medium

Plasma Turbulence n One of the main topics of our theoretical group. Goals: n Explain turbulence in MST experiment n turbulence in the Solar wind n turbulence in the Interstellar Medium

Dalton Schnack Computational Physics Fluid models of plasmas Plasmas in astrophysics

Research Interests n Magnetohydrodynamics (MHD) n Extended MHD (2-fluid/FLR effects) n Fluid models for tokamak plasmas (closures) n Plasma relaxation/dynamo n Large scale computations for fluid plasmas n MHD/RF interactions n Anomalous angular momentum transport in magnetized plasmas n Structure and heating of the solar corona n Accretion disk coronae

Cary Forest

The MST Experiment (Madison Symmetric Torus) a “reversed field pinch (RFP)”

MST minor radius = 0.5m current < 0.5 kA, T ~ 10 7 k, n ~ cm -3

The confining magnetic field is weak Plasma is relatively unstablean advantage for fusion energy Magnetic fluctuations are largeneed to reduce energy loss Energy is lost rapidly

The purpose of MST research n Fundamental plasma physics n The RFP as a fusion concept n Fundamental plasma physics in common with astrophysics

Magnetic self-organization MST toroidal magnetic flux heat flux (MW/m 2 ) rotation (km/s) ion temperature (keV) dynamo magnetic fluctuations energy transport momentum transport ion heating time (ms)

for fusion energy learn to suppress magnetic self-organization for astrophysics understand magnetic self-organization common to lab and cosmos

Plasma properties measured with n Lasers n Neutral atom beams n Ion beams n Spectroscopy and more

plasma controlled with n EM waves n Induced electric fields n Neutral beams

Graduate student research on MST n MST is a team effort with strong scientific and technical interactions; very dynamic n Many mentors available for graduate students n Each student “owns” a physics problem n Many physics and instrumentation opportunities

Stewart Prager

Purpose: To understand major plasma physics problems critical to laboratory and astrophysical plasmas Unites Laboratory and astrophysical scientists Experiments, theory, and computation Tests Astrophysical ideas that can be studied in the lab The NSF Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas

Magnetic Self-Organization Magnetic field (and related quantities) spontaneously rearranges itself Solar surface

Physics Topics n Dynamo n Magnetic reconnection n Angular momentum transport n Ion heating n Magnetic chaos Spans plasma phenomena in solar wind, sun, accretion disks, galactic clusters…

Institutions The University of Wisconsin Princeton University The University of Chicago Science Applications International Corp Swarthmore College Lawrence Livermore National Laboratory Los Alamos National Laboratory University of New Hampshire Includes experiments at UW, Princeton, Livermore, Swarthmore