Probing High Density Plasmas with Soft X-Ray Lasers

Collisionally pumped x-ray lasers are ideal for a wide variety of plasma diagnostics. They have been demonstrated over a wavelength range extending from 3.5 nm to 40 nm and have output energies as high as 10 mJ in 150 ps pulses. The beam divergence is less than 15 mrad and the linewidth λ/∆λ~10 provides sufficient longitudinal coherence for interferometry. Using various arrangements constructed with multi-layer XUV reflective optics we have carried out a variety of experiments with the yttrium x-ray laser operating at 15.5 nm. Initial experiments involved x-ray laser backlighting and Moiré deflectometry, while later work demonstrated interferometric determinations of plasma density profiles in various targets. We have also studied hydrodynamic imprinting of laser speckle patterns on directly driven thin foils with 1-2 μm spatial resolution. These detailed plasma diagnostic capabilities provide an important means to benchmark hydrodynamic calculations of dense plasma flows.