HOLLOW CATHODE PROFILE AND BLAST WAVES

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HOLLOW CATHODE PROFILE AND BLAST WAVES

• Alberto MAROCCHINO1,2, J. P. Chittenden1, A.
  Ciardi1,2, C. Stehle2, S. V. Lebedev1, F. A.
  Suzuki Vidal1, S. Bland1, S. Bott1,4, G. Hall1,
  J. Palmer1,3, A. Harvey1
• 1 Plasma Physics Group, Imperial College of
  London
• 2 Observatoire astronomique de Paris, Meudon,
  France
• 3 AWE, U.K.
• 4 UCSD, San Diego, California, USA
• JETSET school Torino 2007

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Layout

• Introduction
• Hollow cathode
• Geometry
• Physics
• Simulations
• Some diagnostics
• Comments
• Blast waves
• Introduction
• Theoretical results
• First simulations
• Future plans
• Summary and Conclusions

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Suggestion!
Astrophysicists may find a nice inspiration from
the laboratory astrophysics. A simple situation
allows us to have more control about the
underlying physics.
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Hollow cathode geometry

• From Lab. Astrophysics (Lebedev at al. Ciardi et
  al.) it is possible to generate a jet using a
  particular Z-pinch configuration
• The new geometry allows us to generate two
  different and quasi-symmetric jets
• The importance of the simulation is also linked
  with basic shock-waves theory and plasma fusion
• Lay-Out
• Cathode radius12.5 mm
• Anode radius 2 3 4 mm
• Anode thickness 1 mm

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Physics (?)

• The Hall force produced by the anode and cathode
  pushes upward the plasma
• The new geometry drives the hall force to
  compress on axis the ablated plasma
• The plasma is pinched on axis and the precursor
  breaks
• Two jets are formed
• The main one is upward, the downward is smaller
  (the two videos will show clearly this
  phenomenon)
• Lebedevs formula to study the mass forming the
  precursor (1 mm)

Ciardi et Al. Journal of Ast.
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Simulations

• 3D Resistive Radiative MHD Simulations

Marocchino A. IC transfer rep.
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Simulations

• 3D Resistive Radiative MHD Simulations Section

Marocchino A. IC transfer rep.
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Post Processing

• First ablation plasma generates uniform
  background.
• After the wires breakage (200 ns) a bigger
  quantity of mass is released and pinched (mass
  7.0 10-5 g).
• The plasma column breaks (260 ns)
• The entering mass depends on the cathode
  dimension
• If too far away the pinching is even more
  difficult
• The more space traveled by the plasma implies
  longer time to the pinch time
• Approximately we have a 4.0 10-5 g entering the
  hollow cathode

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Post Processing

• For the formed jets we have the following
  parameters
• ß 2
• Ma 50
• ReM 18(?) 24(?)
• Pe 40(?) 20(?)
• ? ???
• The dimensionless parameters denote that the
  laboratory astrophysics is in the same range than
  astrophysics

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Laser Cluster
LASER CLUSTER INTERACTION
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Blast Waves

• Studying different shocks waves
• Coulomb Explosion induced in a Cluster material
  by a Laser
• Cluster H Ar Kr Xe
• Laser IC facility 335 mJ
• Laser spot 75 µm
• For 3D simulation 3.5 mm thickness
• 2D simulation Cylindrical
• 3D simulation 2 conical blast waves colliding

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2D Blast waves

• Theoretical results predict for a cylindrical H
  Blast Waves R(t)t-0.5
• Our simulations predict a value of 0.44
• Encouraging results for Kr Xe
• Work in progress Corner fluxes, new flux
  limiter routines, X-ray tracing

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Conclusions

• Radial array
• New geometry under investigation
• Comparison with astrophysical jets thru
  dimensionless parameters
• New routines
• Precursor modeling
• Blast waves
• Numerical problems to solve (corner fluxes,
  thermal instabilities)
• Code validation

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this is the end
THE END