STRONGLY COUPLED PLASMAS

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STRONGLY COUPLED PLASMAS
Nearly Perfect Fluids 2009
MICHAEL S. MURILLO LOS ALAMOS NATIONAL LABORATORY

• Special thanks to
• Prof. John Goree (Univ. Of Iowa)
• Prof. Tom Killian (Rice Univ.)

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Plasma Physics Spans a Wide Range of Conditions
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Strongly Coupled Plasmas - What Are They?
Coulomb Coupling Parameters
ion-sphere radius

• Strong coupling is some combination of
• high charge
• high density
• low temperature

There are other, embellished Coulomb Coupling
Parameters.
degeneracy parameter
Quantum (Pauli exclusion)
Screening
warm dense matter
E.g., ions screened by electrons.
E.g., electrons or very dense ions.
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Strongly Coupled Plasmas - Some Examples
giant planets
non-neutral
neutral
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Dusty Plasmas
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What is a Dusty Plasma?
Laboratory experiments motivated by what was a
problematic situation.
Today, this situation is created carefully and
purposefully.
Dusty plasmas occur widely in the universe.
A dusty plasma is a normal plasma with
micron-sized impurities.
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How Are Dusty Plasma Experiments Performed?
Konopka U et al. PRL 84, 891 (2000)
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Two-Dimensional Crystallization Studies
Structure factor
Raw images
Solid
Plaser 1.4 W
Liquid
Plaser 4.4 W
g(r)
Voronoi tessellation
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Collective Excitations in Dusty Plasmas
no excitation
How are Ion-Acoustic Waves (IAWs) changed under
strong coupling conditions?
and many others
laser excitation
Transverse waves are a signature of strong
coupling.
and many others
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Wave Behavior in 2D Dusty Plasmas
BDBrownian dynamics (MD)
(accepted PRE)
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Ultracold Plasmas
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Neutral Plasmas Near Absolute Zero Impossible?
Ionization Potential
Rydberg Levels
Photoionization 412 nm
1P1
Cooling laser 461 nm
Start with a millimeter-size cloud of laser
cooled atoms
1S0
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Absorption Yield Spatial and Ion Doppler
Information
plasma
422 nm laser
y
z
false-color camera image
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Plasmas Near Absolute Zero Impossible?
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Rapid Heating Disorder-Induced Heating
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Temperature Oscillations
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Ultracold Plasmas as Ultrafast Optically-Modified
Many-Body Systems
Then, the system (plasma) evolves on a different
energy surface.
optical modification of U(rN)
Initially, the system (cold gas) evolves on this
energy surface.
To have a temperature oscillation, this quantity
must change sign. Therefore, the flow of current
relative to the force must change sign.
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Molecular Dynamics Confirm Prediction
Note points
ballistic blast
ballistic blast
rebound
overshoot
overshoot
rebound complete reversal of current
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Dense Plasmas
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Inertial Confinement Fusion
One of the two major efforts toward controlled
fusion energy is inertial fusion, which
utilizes high density and highly transient
conditions.
Tokamaks are low density, long confinement
machines.

• ICF is made possible by very large, usually
  laser, drivers
• NIF at LLNL
• Omega at Univ. of Rochester
• Z-machine at SNL
• HIF at LBNL
• Etc.

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Inertial Confinement Fusion Turbulent Mixing and
Viscosity
Imperfections, such as drive asymmetries and
material inhomogeneities, mixes fuel with drive
layers.
Rayleigh-Taylor mixing
The growth of such instabilities is characterized
by the Reynolds Number
Viscosity plays a key role.
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A Simple Dense Plasma Viscosity Model
Step ! Atomic physics, finite temperature and
pressure
cell model
solve finite-temperature Thomas-Fermi in cell
Step !I From the solution compute ionization
level and screening length this defines a
Yukawa model

• Features
• Finite radius includes pressure ionization
• Fermi statiistics describes bothbound and free
  states
• Easy to compute at any temperature

Fit to MD results
data

• Liquids metals are good test case
• very strongly coupled
• Thomas-Fermi will be at its worst
• there is experimental data

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Can The Viscosity Be Measured? Can Anything Be
Measured?
Probing dense, SCP is very difficult, but X-ray
Thomson scattering (XRTS) shows promise X-rays
can enter and exit the material
In general, x-rays scatter mainly from electrons
(bound and free). This problem is very well
studied in the context of liquid-metal research,
and the main result is
atomic form factor (FT of bound density)
screening cloud (FT of free density)
uniform portion of free electrons
core electrons
ion diffusive motion
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Modified Navier-Stokes Form Of Ion Dynamical
Structure Factor
From the (longitudinal) Navier-Stokes equation
(plus continuity equation)
One can construct the ion DSF
The Navier-Stokes form violates basic sum rules
S(q) is the Fourier transform of g(r)
nonlocal compressibility
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Ion-Acoustic Waves in WDM
Consider warm, dense Be
Viscosity affects wave dispersion at short
wavelengths.
Viscosity greatly damps the IAW - providing a
possibility of a measurement with XRTS.
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SUMMARY, CONCLUSIONS, AND OUTLOOK

• Strongly coupled plasma physics is a diverse
  subset of plasma physics.
• Dusty plasmas are strongly coupled plasmas that
  have high charge.
• Dusty plasmas allow us to address the classical
  many-body problem.
• A strength of dusty plasmas is the ability to
  actually measure all particle motions.
• Ultracold plasmas are strongly coupled plasmas
  that have very low average kinetic energy.
• Ultracold plasmas allow us to carefully explore
  the physics of non-equilibrium systems.
• Because they are dilute, timescales are
  effectively slowed because the density is low.
• Dense plasma are strongly coupled because the
  inter-particle separation is small.
• Dense plasmas, beyond astrophysical interest,
  are of great importance to fusion energy.
• An important aspect of dense plasmas is
  temperature and pressure ionization (atomic
  physics).

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Ultrafast Systems in General The Bigger Picture

• Ultrafast dynamics occurs widely
• artificial molecular machines
• M. A. Garcia-Garibay, Nature Materials 7, 431
  (2008)
• photo-isomerization processes in biology
• B. Perman et al., Science 279, 1946 (1998)
• non-thermal melting
• C. W. Siders et al., Science 286, 1340 (1999)
• A. M. Lindenberg et al. Science 308, 392 (2005)
• B. J. Siwick et al., Science 302, 1382 (2003)

photoactive yellow protein
Ge
QGP?
InSb
Al