Fast ion acceleration from thin foils irradiated by ultra-high intensity, ultra-high contrast laser pulses

Ion acceleration resulting from the interaction of ultra-high intensity (2 × 10²⁰ W/cm²) and ultra-high contrast (∼10 ¹⁰) laser pulses with 0.05-10 m thick Al foils at normal (0) and 35 laser incidence is investigated. When decreasing the target thickness from 10 m down to 0.05 μm, the accelerated ions become less divergent and the ion flux increases, particularly at normal (0°) laser incidence on the target. A laser energy conversion into protons of ∼6.5% is estimated at 35° laser incidence. Experimental results are in reasonable agreement with theoretical estimates and can be a benchmark for further theoretical and computational work.