Increased hot electron production from the addition of a gas cell in sub-picosecond laser–foil interactions

Abstract

A number of recent experiments at the VULCAN laser at the Rutherford Appleton Laboratory involving high intensity (1019 W/cm2) sub-picosecond laser pulses incident on thin (∼10 μm) metal foils for use as a proton probe have suggested that the addition of a gas cell behind the foil results in a significant increase in the production of hard x rays, particularly in the direction counter to the incident laser direction. In this paper, we consider two mechanisms that might contribute to this effect. Analysis of these two mechanisms indicates that there are plausible physical mechanisms that could give rise to the observations, and thus the physics of these gas-cell targets merits further study.