Transonic Radiation Flow in Aerogel Foams as a New Power Diagnostic on Z

Summary form only given. The Sandia Z dynamic hohlraum radiation drive produces high radiation powers and energies. Using these high powers and energies, a new in-situ diagnostic has been developed and tested, that uses the super-sonic to sub-sonic transition of a Marshak radiation wave in a cylindrical block of SiO₂ aerogel foam. When this transition takes place, a shock is launched, with a velocity much less than the preceding Marshak wave, and the resulting density enhancement in the foam can be radiographed. This process is analogous to the creation of a radiation "fireball" which results in a "blast wave" shock. A successful demonstration of this diagnostic technique was achieved in the Z-1430 experiment on 25 Jan 2005. Data and simulations of this experiment are presented and the sensitivity to drive power and other variables is indicated.