Comparison of laser ion acceleration from the front and rear surfaces of thin foils

The comparative efficiency and beam characteristics of high-energy ions generated by high-intensity short-pulse lasers (∼ 1-6 × 10 ¹⁹ W/cm²) from both the front and rear surfaces of thin metal foils have been measured under identical conditions. Using direct beam measurements and nuclear activation techniques, we find that rear-surface acceleration produces higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. Our observations are well reproduced by realistic particle-in-cell simulations, and we predict optimal criteria for future applications.