Numerical Modeling of Radiation for the NRL ArF* Laser

The US Naval Research Laboratory (NRL) is the world leader in the development of high energy excimer laser science and technology [1] . The argon fluoride (ArF*) laser can be scaled in power and energy to become a good candidate for direct or indirect driver for inertial confinement fusion (ICF). The deep UV light (193 nm) provides uniform target irradiation and broad native bandwidth (5 to 10 THz), suppresses laser plasma instabilities, and has intrinsic efficiency of more than 16 %. In this work we present the progress in modeling the kinetics and radiation of an electron beam ( e -beam) pumped ArF* laser relevant to NRL Electra facility. The modeling is based on the NRL Orestes suit of codes. The most important parameters used for guiding the experiments and monitoring the Orestes predictive capabilities are the laser yield and ASE. Here we present some numerical simulations for 0.5–1 MW⁄cm 3 e -beam power and total pressure 12–20 psi. We scan the range of pressures for which experiments are typically performed [2] . The ASE is a small fraction of the laser yield, on the order of 1-10 %. The numerical simulations show that the laser yield is not very sensitive to total pressure, which should be close to 1 atm, but very sensitive to F 2 content: maximum lasing is observed at 0.5±0.2% F 2 in Ar. The laser yield increases with e -beam power deposition until it reaches an optimum e -beam power beyond which the lasing decreases because most of the ArF* molecules are dissociated by electron impact or lost in neutral-neutral collisons with Ar and F 2 .