3D wall motion in hohlraum

Inside a hohlraum, the plasma blow-off of the wall heated by laser beams is a serious concern as this determines how the laser beams propagate through the hohlraum and where they subsequently deposit their energy in the hohlraum. In turn, this determines the X-ray drive that an ICF capsule sees, and therefore impacts the symmetry of the implosion. It is clear that there is here a need to benchmark wall motion in simulations with experimental measurements. Recently, a series of experiments have been carried out on the Omega laser facility to examine such an issue. In an open cylinder, the motion of the laser-driven plasma bubbles was observed with proton radiography. A nearly uniform irradiation of the 59° laser cone with 10 laser spots was compared to the classic irradiation with 5 laser spots for which more 3D effects are expected

We present here 2D and 3D calculations of these experiments. The impact of the 3D is demonstrated: the 3D-calculated bubbles move faster than the 2D-calculated ones. Radial velocities are supersonic (Mach=3-5) and exceed 1000 km/s. However, the 3D calculations still underestimate the experimentally measured bubble motion.