Implosion Symmetry of

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Implosion Symmetry of Laser-Irradiated
Cylindrical Targets
R. Ramis, J.Ramirez
E. T. S. I. Aeronáuticos. Univ. Politécnica
Madrid (SPAIN)
G. Schurtz
CELIA, Univ. Bordeaux 1 (FRANCE)
Paper O2.023, 32nd EPS Plasma Physics Conference,
Tarragona, 27 June- 1 July 2005
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OCTALIL cylindrical target
Preliminary design to be shoot at the Ligne
d'Intégration Laser, upgraded with two
qauadruplets. Expected to take place in Burdeaux
in 2008-2009
50 kJ in 5 ns 8 beams in octahedric configuration
CH shell 0.6 mm of radius 40 mm thickness
Filling DD at 30 bars
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Issues on experiment planing

• Complex laser plasma interaction
  (hydrodynamics, transport, absorption, ...)
  determine the implosion characteristics.
• Static irradiation (no motion) codes give only an
  estimate of the implossion uniformity based on
  simple scaling laws (i.e. Pa I ? )
• This aproach can be justified a the begining of
  the irradiation.
• Numerical simulation is needed for later times

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- 2
2
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Numerical approach code MULTI

• Includes basic physics of laser plasma
  interaction in 1D or 2D (poster P5.107 in this
  conference)
• Hydrodynamics (Lagrangian/Eulerian)
• Unstructured grids
• Heat transport (Spitzer flux limiter)
• Laser deposition (Bremstrahlung, 3D-ray tracing)
• Radiation transport
• Two temperatures (in 1D version only)
• Additional plug-ins for fusion reactions and
  a-transport
• 3D version not yet available.

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MULTI aplications
1D cylinder
Ablative non-linear RT instability
2 ns
1 ns
3 ns
4ns
0 ns
r (g/cm3)
R(cm)
Fast ignition
Hohlraum target
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MULTI environment

• MULTI is writen using a special computer language
  (r94) and C
• User interface
• Graphic program to plot
• Curves
• Surfaces
• Isocontours
• Runs on Linux
• Current version
• multi2002.tar.gz
• 1107920 bytes

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MULTI web server
http//server.faia.upm.es/multi
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Longitudinal uniformity issues

• In the best case (uniform irradiation), only a
  section of the target implodes.
• End effects (jets ?) take place.
• How long is the cylindrical part ?
• How are related Xlaser and Xcore?

jet
jet
Xcore
Xlaser
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Longitudinal 2D simulations
s
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Longitudinal simulation
Initial
Density
Temperature
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Longitudinal simulation
0.5 ns
Density
Temperature
12
Longitudinal simulation
1.0 ns
Density
Temperature
13
Longitudinal simulation
1.5 ns
Density
Temperature
14
Longitudinal simulation
2.0 ns
Density
Temperature
15
Longitudinal simulation
2.5 ns
Density
Temperature
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Longitudinal simulation
3.0 ns
Density
Temperature
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Longitudinal simulation
3.5 ns
Density
Temperature
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Longitudinal simulation
4.0 ns
Density
Temperature
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Longitudinal simulation
4.5 ns
Density
Temperature
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Longitudinal simulation
5.0 ns
Density
Temperature
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Longitudinal simulation
5.5 ns
Density
Temperature
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Two configurations have been identified
The position of right and left beam rings can be
adjusted for
A) Maximum compression
B) Maximum uniformity
1 mm
Too separated
Too close
2.5 mm
Optimum
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Deuterium reaches 1-5 g/cm3
4 g/cm3
2.2 g/cm3
CH ablator
Option A
Option B
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Azimuthal uniformity issues

• In the best case (infinite cylinder), the finite
  number of beam directions can produce azimuthal
  distortions.
• The attainable density is limited by this fact.
• An optimum beam radius has to be found.

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Transversal 2D simulations

• Planar 2D geometry
• 2D ray tracing
• ½ grid (by technical reasons)
• Gaussian beams

s
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Transversal simulations
Initial
Density
Temperature
Grid
Power density
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Transversal simulations
0.5 ns
Density
Temperature
Grid
Power density
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Transversal simulations
1.0 ns
Density
Temperature
Grid
Power density
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Transversal simulations
1.5 ns
Density
Temperature
Grid
Power density
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Transversal simulations
2.0 ns
Density
Temperature
Grid
Power density
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Transversal simulations
2.5 ns
Density
Temperature
Grid
Power density
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Transversal simulations
3.0 ns
Density
Temperature
Grid
Power density
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Transversal simulations
3.5 ns
Density
Temperature
Grid
Power density
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Azimuthal symmetry
s0.03 mm
s0.06 mm
s0.12 mm
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Final configuration for sr
Thermal wave front
CH
DD
Density g/cm3
cm
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Summary

• Cylindrical target experiments proposed for
  OCTALIL have been analized.
• Two design points have been identified
• High compresion (1 mm at 4 g/cm3)
• Long configuration (2.5 mm at 2.2 g/cm3)
• Cross section 2D simulations show reasonable
  symmetry