As the fiducial foils heat, they go through several different ionization stages. Each ion stage absorbs different frequencies from the x-ray backlighting spectrum. The streak camera records the ionization history of each of the fiducial foils in the tube. From this, the time history of the temperature of each foil can be inferred. 10 presents an example of a streak-camera data record of backlight passing through a tube in the experimental setup shown in Fig.
Time runs horizontally and the spectrum is vertical.
At early time the silicon K-alpha lines are seen. As the radiation flows up the tube, at late time, the aluminum K-alpha lines rise up. These initial experiments have also been extended using smaller hohlraums that create hotter radiation sources capable of driving longer and more complex two-dimensional geometries. The radiative drives from these hotter sources have also been well-characterized. These advances have brought us to a position where detailed radiation hydrodynamics simulations are available and detailed kinetics models can be produced, with some effort.