Proton Beam Focusing Using Novel Structured Targets

For proton cone-guided FI, the proton source foil is placed within a cone, which can affect the proton beam properties (i.e. focusing, conversion efficiency and maximum energy). The effect of a surrounding structure on the proton beam properties has been investigated using the Trident laser at LANL delivering 80 J in 0.5 ps. High-density carbon hemispherical shells (600 $\mu m$ diameter, 10 $\mu m$ thick) were placed at the end of an aluminum structure, where the segment capped a cylindrical or conical hole and were compared to ``freestanding'' shells. A stack of RCF and a Cu mesh placed rear target normal was used to diagnose the beam properties. Results show that surrounding the hemisphere with a structure not only changed the maximum proton energy but also reduced the conversion efficiency. Comparison of experimental results with LSP modeling will be discussed.