9 research outputs found
Shock impedance matching experiments in foam-solid targets and implications for "foam buffered ICF"
We studied the influence of foams on laser produced
shocks. Experiments were performed at LULI using a Nd laser
converted to second harmonic, and at MPQ (Max Planck Institut
fĂĽr Quantenoptik) using the iodine Asterix laser converted
to third harmonic. In both cases, sub-ns lasers with pulse
energies of several tens of joules were focused on large
focal spots (hundreds of microns) to reduce 2D effects.
The laser beams were optically smoothed with phase zone
plates (PZP) and directly focused on layered targets made
of a foam layer on the laser side and a stepped Al layer
on the other side. A visible streak camera was used to
detect shock breakthrough at the base and at the step of
the Al target, allowing shock velocity to be determined.
Using the well known SESAME Al equation of state, we determined
shock pressure. A stronger pressure increase was measured
when foam was present, compared to what was obtained by
focusing the laser beam directly on the Al target. This
was due to the impedance mismatch effect at the Al-foam
interface
Design, simulation and application of phase plates
In this paper we analyze the use of phase plates to obtain
homogeneous laser intensity profiles. We studied the dependence of
intensity distribution on phase plates characteristics, we
obtained analytical solution for the intensity profile in the
focal plane for plane waves and developed a numerical simulator to
calculate the intensity distribution with a generic initial beam
and at any propagation plane. We defined criteria to evaluate the
quality of profiles produced by different phase plates. Finally we
compared experimental results obtained at the Max-Planck Institut
fĂĽr Quantenoptik of Garching with our numerical simulations
Production of high quality shocks for equation of state experiments
In this paper we describe the quality requirements that a shock wave must fulfil to make equation of state (EOS) measurements possible: planarity, no-preheating and stationarity of the shock. Experimental measurements have been performed at the Max Planck Institut fĂĽr Quantenoptik (Garching). We also present simple analytical models that allow to verify shock stationarity and absence of preheating