This requires exacting procedures that provide the temperature, density, and gradient scale lengths on a single experiment. The x-ray absorption of opacity samples was measured by the method of point projection spectroscopy, which is illustrated in Fig. 7 . In this experiment, eight of the laser beams at Nova are used to heat the opacity sample. Other x-rays from the same point backlight bypass the sample, but are still diffracted from the crystal onto the film record. Because the crystal disperses the spectrum, the result is an image that is both spatially and spectrally resolved.
Temporal resolution is provided by backlight duration.
Schematic of point projection spectroscopy method for measuring opacity. Proper collimation allows a highly quantitative analysis of the spectrum. Careful attention was paid to the sample conditions. It was required that the sample be uniform throughout in both temperature and density. Uniformity of temperature was attained by heating the sample in a special hohlraum.