Experiments on energy redistribution by thermal radiation in cylindrical cavities

Experiments are presented that demonstrate the process leading to isotropization of the radiation field in a cavity heated by thermal x rays. Gold, cylindrical cavities 500 {μ}m in diameter were heated from one side by {}154 eV thermal radiation from a laser plasma. The effect of the reemission in transporting energy along the cylinder axis was ascertained by comparing the axial temperature profile of ``open'' and ``closed'' geometry targets. The results are in good agreement with a theoretical model for the redistribution of energy via absorption and re-emission of thermal radiation.