Proof of principle experiments that demonstrate utility of cocktail hohlraums for indirect drive ignition

Abstract

This work is a summary of experiments, numerical simulations, and analytic modeling that demonstrate improved radiation confinement when changing from a hohlraum made from gold to one made from a mixture of high Z materials (“cocktail”). First, the results from several previous planar sample experiments are described that demonstrated the potential of cocktail wall materials. Then a series of more recent experiments are described in which the radiation temperatures of hohlraums made from uranium-based cocktails were directly measured and compared with a gold reference hohlraum. Cocktail hohlraums meeting the oxygen specification (<5% atomic fraction oxygen) demonstrated an increase in radiation of up to 7 eV, agreeing well with modeling. When applied to an indirectly driven fusion capsule absorbing ∼160kJ of x-ray energy, these data suggest that a hohlraum made from a suitably chosen uranium-based cocktail would have about 17% less wall losses and require about 10% less laser energy than a gold hohlraum of the same size.