Geometric scaling of laser-driven proton focusing from hemispherical foils

Abstract

We systematically characterize the focusing behavior of laser-driven proton beams from hemispherical targets of various diameters using mesh radiography. The proton focal location is inferred to be near the geometrical center for the smallest tested hemisphere ($\hat{I}¨=D_{hemi}/D_{Laser}=6.1$). However, larger hemispheres ($\hat{I}¨=14.6$) degrade the focusing behavior and behave more like flat foils with focal location significantly inside the hemisphere. We also infer a tight virtual focus of $9\pm 3\hat{I}¼$m through a mesh transition analysis.

9 pages, 9 figures