Diapositive 1

1
Shock ignition modelling elements and target
robustness M. Lafon, X. Ribeyre and G. Schurtz
Centre Lasers Intenses et Applications,
Université Bordeaux 1- CNRS - CEA
Iso-thermonuclear energy curves
Run series of CHIC 1D using radial rays and total
energy absorption at critical
Ribeyre, X et al., Plasma Phys. Cont. Fusion, 51,
015013 (2009)
How does it work ?
Ignition pulse robustness
Spike power time shape
Laser time rise TR TF 200 ps
If spike duration decreases about 50,
thermonuclear energy only decreases about 15
Pulse duration at FWHM TM?TTD
The spike power remains constant PScte
The ignition mainly depends on the spike power
and not on the spike energy

• A strong convergent shock is produced by
  ignition pulse
• The ignitor shock catches up the compression
  shock reflected at the center of the target near
  the inner interface of the shell
• The resulting assembly shows that the hot spot
  pressure is greater than the surrounding fuel
  pressure that leads to ignition

Non-isobaric configuration
For all targets
In the shock ignition scheme, the high
nonisobaric nature of the final fuel leads to
achieve the ignition conditions
The intensity threshold required for ignition is
not homothetic Pshock is not varying by h²
The required spike power strongly increases when
the implosion velocity decreases (lt 240
km/s) Beyond 350 km/s, the HIPER target
self-ignites
There is to reach a compromise between the
target intensity and the implosion velocity
In the shock ignition scheme, the implosion
velocity field is optimal for the range
240 lt Vimp (km/s) lt 290

• Runs of simulations 1D shows the robustness of
  the shock ignition scheme
• The spike impulsion leading to ignition mainly
  depends on spike power and not on spike energy
• The Rosen model study shows the influence of the
  non-isobaric parameter at constant mass, the
  laser energy required for ignition is lower for
  the shock ignition scheme than for the classical
  isobaric configuration scheme
• The shock ignition pressure evolution is
  well-described by the Guderley model during
  convergence
• The required spike laser power family is not
  homothetic with the target size for a family of
  homothetic targets the power threshold does not
  increase as much as the homothetic factor of the
  target size
• An optimal domain of use might be defined by
  making a compromise between the intensity on
  target and the implosion velocity
• A study on 2D effetcs will be performed
• The analytical model has to be detailed and
  improved using the Guderley model in order to
  best describe the shock dynamics
• Hydrodynamic instabilities have to be evaluated
  according to the target irradiation symmetry
• The limiting factors of laser-plasma interaction
  must be defined, especially concerning the
  parametric instabilities