Development of a Broadband VIS/NIR Reflectivity Diagnostic for Dynamic Shock Compression Experiments

Broadband reflectivity measurements provide detailed information about the optical and electronic properties of shocked matter, complementing other spectroscopic techniques and increasing the accuracy of pyrometric measurements, which is vital for improving models of planetary cores. A time resolved broadband VIS/NIR reflectivity diagnostic was constructed and recently tested at the Jupiter Laser Facility at Lawrence Livermore National Lab and determined to be a viable technique for obtaining spectrally resolved reflectivity data during shock compression. A 50-100 fs 800 nm pulse was first sent through a pulse stacker and then an intense white light pulse with wavelengths from ~400 nm to ~1200 nm was generated by focusing the stacked pulses into a calcium fluoride crystal. The white light pulses were then sent into the chamber and reflected from the target surface. The reflected light was dispersed using a custom spectrometer which was coupled to a ROSS streak camera with an S1 photocathode, allowing for light collection across the entire wavelength band listed above. Reflectivity measurements were obtained for various targets during the aforementioned campaign with one ns time resolution and 0.53 nm wavelength resolution.