Laser driven flash X-ray radiography of shocked materials

Short-pulse laser driven x-ray radiography offers the potential to improve spatial and temporal resolution for imaging of shockwaves within materials. Previous studies have primarily used x-rays ⪅10 keV to image internal shockwaves or shock-induced fragmentation. Here x-rays in the tens to hundreds of keV are used to image a chromium foil with an internal shockwave of ~100 μm width and a factor of two increase in density. Performance of two experimental configurations was compared for both static and dynamic flash x-ray radiography at the OMEGA-EP facility. Experimental results are compared to synthetic radiographs generated using a combination of Particle-In-Cell and MCNP simulations and a ray-tracing program. Configuration one used a Ta cube target and displayed poor image quality due to presence of a dual x-ray source and high background. Configuration two had much better image quality using a Compound Parabolic Concentrator (CPC) cone with a Ta wire target to physically limit x-ray source, a magnetic field to deflect electrons, and a Cu casing to shield the sides and back of the image plate pack. By varying the short pulse beam delay driving the flash x-ray source spatial-temporal variations in shockwave dynamics (i.e., position, width, density profile) were resolved within the Cr foil, yielding results consistent with corresponding one-dimensional Helios hydrodynamic simulations. This supports extension of this technique to conduct shockwave diagnostics for cases less amenable to 1D modelling.