Planar Laser-Induced Fluorescence Developed for Laser Plasma Accelerator Targets

The ability to precisely shape gas jets for controlled injection of electrons in laser plasma accelerators (LPAs) is crucial for developing high quality electron beams. Verifying tailored density profiles has called for more detailed gas density diagnostics than those traditionally used. Most diagnostics give line-of-sight measurements, integrating over and blurring sharp asymmetric features. In this study, planar laser-induced fluorescence (PLIF) has been prototyped for characterizing laser plasma accelerator gas jet targets. PLIF has the distinct advantage of isolating a two-dimensional slice of the jet plume using a laser sheet. As a demonstration, gas jets whose flows were intercepted by a razor blade were characterized with PLIF. Fluorescent slices of the gas jet resulted in high resolution images which revealed changes in characteristic flow parameters with change in blade position. It was shown that PLIF is able to resolve thin features such as gas density shocks and other features on scales relevant for tailored LPA gas jet targets.