Ultra-Low Density Foam Targets for Enhanced Laser-Plasma Proton Acceleration

The application of ultra-low density targets in high-power laser interactions with solid materials has received significant attention due to their advantages in ion acceleration. These targets enable efficient energy transfer from the laser pulse to the target by forming a near-critical density plasma, which enhances maximum ion energies. We present a method for creating ultra-low density carbon targets on a thin aluminum foil substrate, supported by detailed characterization and experimental validation using a femtosecond pulsed laser with mJ energy per pulse. The targets' characteristics were assessed through high-speed imaging of their laser interactions, focusing on plasma plume formation and ejection at the target surface, and further analyzed using Langmuir probe diagnostics to measure plasma dynamics. Compared to bare aluminum foils under similar laser conditions, significant differences in plume generation were observed, highlighting the potential for enhanced ion acceleration.