Transcript Laser in protons out

Line broadening / Atomic physics in plasmas
Ladislav Kocbach
University of Bergen,
Bergen, Norway
Atomic physics in laser plasmas
and
line broadening in laser plasmas
Laser-matter interaction
High power laser stories ("Laser in protons out")
Some basic relations
Laser plasmas as source of X-rays
Atomic physics in laser plasmas
Line shapes, broadening
Lorentz, Doppler, Voigt profiles
Stark broadening
Microfields
electron broadening
Simulations
Why are simulations important
Pulse + prepulse
How are simulations done
Laser-matter interaction
what is special
Einstein's "error"
ATI
(High Harmonics)
"Laser light in, protons out"
Photoeffect (photoionization):
The kinetic energy of the electrons is given by the
energy of the photons
and does not depend on the intensity of the light
Multiphoton and Above Threshold Ionization (MPI/ATI)
ATI of rare gas atoms, by 800 nm, 100fs pulses with 1013-1014 W/cm2.
Example of a typical kinetic energy spectrum of photoelectrons
produced by ATI of Xenon.
High power laser stories
"Laser in protons out"
(Future) Medical applications
Nuclear beams without accelerators
VULCAN
NOVA
PETAWATT
NIF - Monster Lasers
Laser Light In, MeV Protons Out (1999)
Livermore's Petawatt, the world's most powerful laser, impinges upon a
target to generate 30 trillion protons from a tiny spot only 400 microns in
size. (Livermore)
Table Top Terawat Laser
NOVA system
Prague Asterix Laser System
PALS
Laser plasmas as source of X-rays
Radiation from laser plasmas
Pulse, prepuls
Spectrum of soft X-rays from Al-plasma
Soft X-ray emission enhanced by a prepulse
Spectrum of x-ray in keV-range from Al-plasma
6
Photon energy [keV]
1.55
1.60
16
2
Intensity [arb.]
Im = 2.3´10 W/cm
1.50
Ka (Al0+– Al4+)
4
2
Hea (Al11+)
Al5+
Al6+
0
0.78
0.80
0.82
Wavelength [nm]
0.84
X-ray emission enhanced by a prepulse
Atomic physics in laser plasmas
Laser-electron interaction, heating
Heating - high degree ionization
Electron-ion collision: ionization
recombinations
light emission and reabsorption
optical thickness
Electron temperature
Ion temperature
Ionization degree
Line shapes, broadening
Line Broadening: Lorentz, Doppler, Voigt
profiles
Stark broadening
electron broadening
Stark broadening
due to the fields of neighbouring ions
Ion microfields
Distribution of microfields (static)
Holtsmark 1919
Microfields determine states of the emiter
n=2 in hydrogen-like ion (atom)
n=3 in hydrogen-like ion (atom)
Holtsmark function used to evaluate the
distribution of electric field strength due to ions.
b is scaled electric field strength.
Stark brodened n=2 to n=1 in hydrogenic ion
(model, from Holtsmarks distribution)
Lya
Stark brodened n=3 to n=1 in hydrogenic ion
(model, from Holtsmarks distribution)
Lyb
Broadening due to electron impact
Which means also
due to the presence of unbound electrons
Classical motion (semiclassical model)
Quantal: Baranger’s formulation
(coherent broadening - single emitor)
The perturbing system:
Continuum electrons present
in the neighboourhood
Their density of states
Their distribution over these
states
This makes the multiparticle
manifold of perturbing states
Generalized formulations
several approaches exist
(fully quantal, semiclassical)
Density matrix formulation
(can incorporate both coherent
and incoherent broadening)
Line shape modeling of multielectron ions in plasmas
P.A. LOBODA, I.A. LITVINENKO,
G.V. BAYDIN, V.V. POPOVA,
and S.V. KOLTCHUGIN
Russian Federal Nuclear Center
All Russian Institute of Technical Physics
Snezhinsk, Chelyabinsk region, Russia
Laser and Particle Beams 18 (2000), 275–289.
Simulations
Why are simulations important
Pulse + prepulse
How are simulations done
Simulations
The plasma dynamics is described via
one-fluid two-temperature Lagrangian "hydrodynamics" codes.
Contains a detailed model of the laser-plasma interaction.
Laser absorption is calculated by numerical solution of
Maxwell’s equations for laser radiation.
A simplified model of atomic physics is included
to calculate the mean ion charge Z.
The populations of the ion charge states
are calculated
from the set of atomic rate equations.
The rates of the collisional ionization,
radiative and three-body recombination,
include the depression of the
ionization potential in dense plasmas.
(one dimensional and
2-dim with cylindrical symmetry)
Results
Ne, Te, Zav, Ti,
Ni (Z)
As function of position
Spectral codes
From
Ne, Te, Zav, Ti,
(more sofisticated can use Ni (Z) )
Evaluate the spectra
1. evaluate detailed configuration populations
2. evaluate line profiles of all the lines
3. combine the spectra from different positions
Conclusion
Line shapes, broadening
Line Broadening: Lorentz, Doppler, Voigt
profiles
Stark broadening
electron broadening
Atomic physics in laser plasmas
Laser-electron interaction, heating
Heating - high degree ionization
Electron-ion collision: ionization
recombinations
light emission and reabsorption
optical thickness
Electron temperature
Ion temperature
Ionization degree
Soft X-ray emission enhanced by a prepulse
Thanks to
Dr. Jiri Limpouch
Prof. Ladislav Drska
Czech Technical University
Eric W. Weisstein
http://www.treasure-troves.com/physics/
Thanks, this is the end
Thanks, this is the end
Thanks, this is the end