Explosive-pusher-type laser compression experiments with neon-filled microballoons

Laser-irradiated targets filled with pure neon have been used to directly measure the peak density ρ and ρR product (density X radius) using spectrally and spatially resolved neon x-ray line emission. In agreement with theoretical predictions for the explosive-pusher mode, we find peak densities in the range 0.25-0.5 g/cm³ which are almost independent of laser power or fill pressure. In addition, ρR values increase from 2 ×{} 10^-4 to 6 ×{} 10^-4 g/cm² as the fill pressure increases from 2 to 56 atm. Using these methods for the density measurement as well as other experimental signatures (such as x-ray pinhole imaging, x-ray streak photography, and x-ray line emission from the glass microballoon), we systematically investigated the explosive-pusher mode of target dynamics for various fill pressures. These and similar methods may become crucial in diagnosing future higher-compression implosions.