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Andrea MACCHICNR/INO, PisaandDipartimento di Fisica “Enrico Fermi”, Università di Pisa
www.df.unipi.it/~macchi
Plasma Physics C: Noninear Plasma Processes and Applications
commons.wikimedia.org/wiki/File:Plasma_lamp_touching.jpg
There's a large variety of Plasmas ...
[Da: T.Killian, Science 316 (2007) 705]
… and an unifying viewpoint
Essential theoretical description: many-body system , dominated by collective dynamics, in most cases of interest far from thermal equilibrium
General problem: understand the coherent dynamics and self-organization of the system and achieve its control to develop applications.
Such control is complex (and challenging) due to the strongly nonlinear nature of the dynamics.
The course aims to focus on some nonlinear phenomenology and related nonlinear models (the most accessible ones ...) with possible emphasis on those problems of most general relevance because of either broad relevance for plasma physics , crossover interest or as examples of general techniques of nonlinear physics
Main Topic: Intense Laser-Plasma Interactions
Laser-Matter Interactions: Extreme Intensities
Plasma is the “only” state of matter in such fields (laser field largely exceeds atomic field => instantaneous ionization)
“Relativistic” plasmaproduced routinely
a0 << 1
- linear response
- effects of magnetic force are negligibile
a0 >> 1
- nonlinear response
- effects of magnetic force are non-negligibile
Relativistic Domain
Applications 1: electron accelerators
principle: “surfing” of electrons on a longitudinalwave with proper phasevelocity
the ”perfect wave”: “wake” of a laser field
T.Katsouleas, Nature 431, 515 (2004); 444, 688 (2006)
Applications 2: ion accelerators
intense research since 2000 based on several schemes:- expansion of a hot plasma- radiation pressure boost- acceleration by shock waves
Review paper:
A. Macchi et al, Rev. Mod. Phys. 85, 751 (2013)
Applications 3: “relativistic engineering”
Idea: “coherent control” of laser-plasma dynamics (e.g. “moving mirrors”) to create/manipulate EM pulses(atto/zeptosecond pulses, high armonics, ultra-high fields ...)
Applications 4: Nuclear Fusion
Glenzer et al., Science 327 (2010) 1228;
O. A. Hurricane et al, Nature (2014), doi:10.1038/nature13008
First results from Laser-Driven Inertial Confinement Fusion experiments at the National Ignition Facility (USA) (lasers.llnl.gov)show scaling of “hohlraum” heating consistent with reaching ignition (fusion energy = input energy)of D-T pellet
Controlled Fusion: a long story ...
Dr Octopus trying to control his fusion experiment in “Spiderman 2” (2004)©Marvel, Columbia Pictures
Strip image from Amazing Spider-Man, #44 ©Marvel comics
Laboratory Astrophysics
S.V.Bulanov et al, Eur. Phys. J. D 55 (2009) 483
Example of relativistic plasma in “exotic” astrophysical environment:Pulsar Magnetosphere
Idea: create similar conditions on a different spatio-temporal scale in the laboratory
LabAstro examples - I
S.V.Bulanov et al, Eur. Phys. J. D 55 (2009) 483
S.V.Bulanov et al, Eur. Phys. J. D 55 (2009) 483
LabAstro examples - II
Towards QED Plasmas and Ultimate Fields?
Ultrahigh fields open up the possibility to investigate exotic effects: radiation friction, pair plasmas, Unruh effect, QED cascades...
Ultimate frontier: approach the QED Schwinger field
Ecr=m
e
2c3/eħ corresponding to I>1029 W/cm2
Physical meaning: eEcrλ
c=m
ec2 => pairs are created from vacuum
two-fold interest for laser-plasma interactions: - use the plasma as an active optical medium for extreme focusing and laser field amplification- describe QED effects in a collective regime
Basic Equations for Collisionless Modeling
Continuity equation in 6D phase space (r,p) for each species a
coupled via momenta of fa to Maxwell's equations
(“natural” units are used!)
Dully approaching this system is often unfeasible analytically and computationally: one needs- models- numerical simulations
Plasmas and Numerical Simulations
Plasma physics offers key and challenging projects for supercomputing with parallel machines(e.g. 2 over 10 starting projects for the Petaflop ROADRUNNER)
“Plasma physics is just waiting for bigger computers”
Back to the roots: plasma discharges
In principle there was the discharge tube …(Faraday, Langmuir, …)
“There are more things between cathode and anode than are dreamt in your philosophy” (H. Raether)
From: J.Reece Roth, “Industrial Plasma Engineering” (IOP, 2004)
“The positive column ... is what I. Langmuir had in mind when he defined plasma”
Nonlinear physics in discharges
Sheath formation near electrodes and ion acceleration:connection with laser-plasma ion accelerators
Stochastic acceleration of electrons in an AC-driven sheath:connection with electron heating in intense laser-solid interaction
Two plasma discharge applications...
Nature: lightning , chemicalreactions in the atmosphere
Industry: microprocessors production by plasma etching
... and many more
Low-temperature discharge plasmas are the basis for many technological and industrial applications: - light sources- electronics (plasma displays)- space propulsion- semiconductor etching for microcircuit production- nanofabrication- surface chemistry: industrial processing of textile or plastic materials - medical applications, sterilization- waste treatment and fuel recovery by plasma cracking- …
Apart from funding opportunities these applications may offer interesting problems
Images selected by T.Andreussi,Dipartimento Ingegneria Aerospaziale,
Università di Pisa