Inference of electron density in NIF capsules from krypton helium-β Stark lineshapes*

The dHIRES x-ray spectrometer measures Kr Heα and Heβ spectra from NIF compressed capsules with 10-eV spectral and 30-ps temporal resolution. Theoretical calculations of the Stark-broadened lineshape of the Heβ complex (3 ³P₁, ¹P₁, ¹D₂) show monotonic variations with density of the line widths, line energies, and intensity of the 3 ³P₁ and 3 ¹D₂ lines relative to the main, 3 ¹P₁ peak. Comparison of the measured Kr Heβ complex line profiles with the theoretical lineshapes provides a measure of the time history of the electron density. These comparisons will be shown for four NIF shots with Kr-doped capsules