Exploring 2ω laser-plasma interactions on the HELEN laser system

We report on an extensive series of experiments using 2ω light on a variety of gaseous targets at the HELEN laser facility at AWE. The aims of the experiments were to investigate laser-plasma interactions and hot electron generation for 2ω light, and to test schemes for efficiently producing multi-keV X-rays. The experiments were diagnosed by an extensive suite of optical and x-ray instrumentation, including streaked SRS and SBS spectrographs, hard X-ray and Dante measurements. The targets used to data have been filled with C5H12, CO2 and Kr. These three targets give very different backscatter, including almost no backscatter from the Kr targets, showing that plasma composition can also be used to minimize backscatter losses. These data also indicate that is possible to produce or quench hot electron production by varying the plasma composition, even near quarter critical density.