Electron Acceleration from the Interaction of VULCAN 100TW Laser with Au Foils and its Dependence on Laser Polarisation

Electrons as well as ions can be accelerated to high energies (MeV) by high intensity laser interactions with solid targets. An overview of an experiment on the Vulcan laser (pulse length c$\tau\sim 150\mu\rm{m}$, energy on target $\sim 60 \rm{J}$), will be presented. In this experiment electron acceleration from thick overdense plasmas is investigated by conducting thickness scans using Au foil targets ranging from 10 to 100 $\mu$m. The electron spectra, of the most energetic electrons produced in the interaction, are measured along the laser direction and extend up to 40MeV. Surprisingly the electron acceleration depends on target thickness. Simultaneously rear surface proton beam profiles show a dependence of target thickness. Both effects are attributed to electron recirculation. In addition the effects of polarisation was investigated. A decrease in number and effective temperature of energetic electrons is observed for circular polarisation as compared to linear polarisation.