Efficient laser-proton acceleration from an insulating foil with an attached small metal disk

Efficient proton acceleration by the interaction of an intense femtosecond laser pulse with a solid foil has been demonstrated. An aluminum coating (thickness: 0.2 μm) on a polyethylene (PE) foil was irradiated at 2 × 10¹⁸ W/cm² intensity. The protons from the aluminum-disk (diameter: 150 μm to 15 mm) foil were accelerated to much higher energy in comparison with conventional targets such as PE and aluminum-coated PE foils. The fast electron signal along the foil surface was significantly higher from the aluminum-coated PE foil. The laser-proton acceleration appeared to be affected to the size of surrounding conductive material.