Transcript Extreme Light: Future Tools for the Shop

Ultra-High-Intensity Laser-Plasma
Interactions: Comparing
Experimental Results with ThreeDimensional,Fully-Relativistic,
Numerical Simultations
Donald Umstadter
Scott Sepke
“Moore’s Law” for Peak Laser
Intensity
eE  mp c 2
Relativistic protons
Peak Intensity (Watts/cm2)
1024
Relativistic nonlinear
optics (free electrons)
eE   me c 2
1018
Nonlinear optics
(bound electrons)
eEr0  e2 / r0
Chirped-pulse
Amplification
(1988)
Mode-locking
103
1
Linear optics
X-ray tube
1900
Laser (1960)
2000
Intense optical laser light can generate
radiation across the entire spectrum
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Type
THz
Infrared
X-rays
Electrons
Positrons
Protons
Neutrons
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Characteristics
Femtosecond
Tunable
Collimated
Synchronized
Bench-top
Bright
Micron source
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Applications
Non-destructive
testing
Radiography
Lithography
Micro-machining
Ultrafast reactions
Metrology
Beam divergence found to be reduced
with increasing laser intensity
LANEX
Plaser =30 TW
E = 180 MeV
Relativistic self-channeling leads to
collimation of the laser beam, which
leads to collimation of the electrons.
r = 1010 e-
tlaser= 30 fs
D ~ 0.25o
tlaser= 400 fs
D = 1°
Laser wakefield plasma waves can accelerate
electons to energy 100 MeV in a single millimeter
F ~I
t 0
Emax at t~/p
t  2 /  p
tl
“Monoenergetic” electrons with energy
exceeding 150 MeV
experimental
result
PIC code
prediction
•J. Faure et al., Nature 431, 541 (2004)
•C.G. R. Geddes et al., Nature 431, 538 (2004)
•S.P.D Mangles et al., Nature 431, 535 (2004)
Particle-in-Cell Laser-Plasma
Simulations
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An exact field and particle motion solver.
Maxwell’s
Equations
E,B Fields
(r, J)
Equation
of Motion
• LSP is a hybrid fluid/particle-in-cell code:
¤ Models include plasmas, lasers, ionization, particle
beams, QMD equations of state, TE and TM modes…
¤ Allows migration between fluid and kinetic solvers.
¤ Uses explicit and stable implicit particle and field solvers.
LSP Particle-in-Cell Simulations
•Fully relativistic 1,2,3D
Cartesian and cylindrical
geometry
•Self-consistent laser-plasma
interactions
Self-injected electrons
Average Velocity
PrairieFire Beowulf Cluster
256 2.2 GHz Opteron (64-bit) processors
128 nodes each containing 4 GB of RAM
Plasma
wave
Plasma
“bubble”
30fs laser
pulse
Longitudinal Electric Field
UNL soon to have a laser with peak powerrate of 1 PW-Hz, highest of any in the US
Peak Power Rate (PW-Hz)
1
30-fs pulse duration
3-J energy per pulse
100-TW peak power
10-Hz repetition rate
Diffraction limited laser focusing
requires exact-field solutions
• Electron deflection experiment/simulations show that
accurate laser fields are essential.
• We have derived exact solutions for arbitrary, focused
Gaussian and super-Gaussian laser profiles.
• These models are complex and must be solved numerically.
Ey
Ez
Ex
Concluding Remarks
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High-intensity laser-plasma interactions (including laser
accelerators) is one of few physical systems in plasma
physics (which is a many-many-body problem) that can
be numerically modeled with reasonable accuracy.
The computing power required for 3-D modeling was
reached only in the last decade.
The availability of greater computing power will enable
simulations with larger domains and longer durations,
which can more accurately model larger interaction
regions and higher plasma densities.
The simultaneous rapid increases in laser and computer
power are good example of technological convergence.