Tuesday, September 24, 2019
Abstract: The Advanced Radiographic Capability (ARC) at the National Ignition Facility (NIF) in Lawrence Livermore National Laboratory (LLNL) is a new Petawatt-class short-pulse laser that is utilized frequently in support of high energy density physics experiments. In contrast to most short pulse laser facilities, ARC operates in an unusual laser parameter space in that it delivers high energy (kilojoule scale) laser beams in long pulse lengths (multi-picoseconds) and large focal spot sizes (~10s of microns). Recent results have demonstrated that ARC can generate protons via the Target Normal Sheath Acceleration (TNSA) with energies that are higher than predicted by the well-known Fuchs proton scaling. [D. Mariscal, et al. POP 2019]. In an effort to investigate proton acceleration in the unique laser parameter regime that ARC inhabits, a series of experiments were performed with the TITAN laser at the Jupiter Laser Facility (JLF). TITAN is a high repetition rate laser, which allowed for a detailed study of how accelerated proton energies scale with key laser parameters like pulse length, laser energy and laser focal spot size. This work details the results of this study and presents a new preliminary scaling for accelerated proton energies via TNSA for multi-ps lasers.