Radiation confinement in x-ray-heated cavities

The confinement of high-temperature thermal radiation in x-ray-heated cavities was studied by relative measurements of the radiation temperature in ``closed'' and ``open'' cavities simultaneously heated by x rays generated in a common laser-heated cavity. The experimental observations provide direct evidence of radiation enhancement due to radiation confinement. We have developed a simple model based on the theory of the radiatively driven heat wave. The predictions of the model are in good agreement with the experimental results.