Laser Wavelength Dependence of Electron and Ion Acceleration Mechanisms in High Intensity Laser-Solid Density Plasma Interactions

We investigate the generation of relativistic electrons and the subsequent ion acceleration due to target-normal sheath acceleration (TNSA) when ultra-intense (I >10¹⁸ W/cm²) short pulse (t_Laser < 10 ps) lasers are incident onto solid density targets as laser wavelength is varied. Scaling laws for the hot electron temperature, T_hot, and the maximum ion energy, E_max, are recast a function of laser wavelength. These predictions are compared to results from Particle-In-Cell (PIC) computer simulations in a variety of geometries, including cases where realistic plasma density profiles as determined by a radiation hydrodynamics code are used. It is found that the wavelength dependence observed in simulation is less pronounced than what is predicted from the well-established scaling laws. An assessment of how switching to longer laser wavelengths, specifically 2 mm Tm:YLF technology, would impact current High Energy Density Science applications and diagnostics is made.