Hot electrons produced from long scale-length laser-produced droplet plasmas

Abstract

Microplasmas produced from 15 μm methanol droplets irradiated by 100 fs laser pulses in the intensity range 10¹⁴–10¹⁶ W cm⁻² are investigated via measurements of the hot electron temperature and X-ray yields under different conditions of intensity, polarization state and plasma scale-length. The scale length of the drop-let plasma is increased with an intentional prepulse that is 10 ns ahead of the main pulse. Hot electron temperatures up to 48 keV have been measured at intensities of 2.5 × 10¹⁵ W cm⁻² and the scaling of temperature as a function of intensity is determined for a long scale-length droplet plasma. The polarization and ellipticity dependence of the hard X-ray yield from the microdroplet plasmas are used to probe the shape of the droplet after irradiation by a prepulse.