Electric field measurements in picosecond laser-produced plasma via X-ray spectroscopy

High resolution, spatially resolved spectroscopy is used to study the interaction of a short 3.4 ps pulse laser at intensities between 1014 and 1017 W/cm2. The detailed lines shapes show a series of regular intensity modulations, or dips, across the spectral line. We present the analysis of the helium-like emission from these aluminium plasmas, and compare the Heβ transition to calculation. Assuming the intensity dips result from the interaction of quasi-monochromatic electric field of a strong plasma wave, we are able to infer the field strengths present and electron density. This suggests that the intensity dips are driven by the strong growth of laser-driven parametric instabilities at quarter critical density. The development of high resolution spectroscopy for the interpretation of parametric driven instabilities in short pulse laser-produced plasma is discussed.