High-Intensity Laser Induced Ion Acceleration from Heavy-Water Droplets

Fusion neutrons from a heavy water droplet target irradiated with laser pulses of $3\times {10}^{19}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$ and from a deuterated secondary target are observed by a time-of-flight (TOF) neutron spectrometer. The observed TOF spectrum can be explained by fusion of deuterium ions simultaneously originating from two different sources: ion acceleration in the laser focus by ponderomotively induced charge separation and target-normal sheath acceleration off the target rear surface. The experimental findings agree well with 3D particle-in-cell simulations.