Enhancing Positron Production using Front Surface Target Structures

Abstract We report the first experimental results and simulations that demonstrate a substantial effect of large-scale front-surface target structures on high-intensity laser-produced positrons. Specifically, as compared to a flat target under nominally the same laser conditions, an optimized Si microwire array target yielded a near 100% increase in the laser-to-positron conversion efficiency and produced a 10 MeV increase in positron energy. Full-scale particle-in-cell simulations that modeled the entire positron production and transport process starting from laser-plasma interactions provided additional insight into the beneficial role of target structuring. The agreement between experimental and simulated spectra suggests future target structure optimization for desired positron sources.