> 65 MeV Protons From Laser-Micro-Cone Target Interactions

We have conducted two sets of laser-ion acceleration experiments at the LANL 200 TW Trident short-pulse laser at ~1020 W/cm² (1 μm, 80-100 J and ~600 fs) at high (>1010) and low (>108) contrast, comparing regular size flat foils (~2 mm by 2 mm), reduced mass targets (200 μm to 500 μm diameter) and new Cu micro-cone targets in three separate geometries (flat-top or pizza-top, funnel, and snub-nose) to elucidate the production of hot electrons [1] and ions in these targets.
Results from the latest experiment show proton energies in excess of ~65 MeV for the pizza-top cones, compared to ~55 MeV for reduced mass targets and ~45 MeV for regular flat foils for high contrast. Data from a Cu Kα 2D imaging crystal, an X-ray single hit CCD, proton beam images on RCF film stacks, and an electron/proton spectrometer are presented and compared, showing the importance of not just generating hot electrons, but in the case of ion acceleration, efficiently propagating these hot electrons to the accelerating “tip”, where they can then be efficiently converted to ion energy, as well as the importance of the micro-cones’ supporting foil size.