A StarDriver-Class Laser Achieving 1 % Beam Uniformity in 1 ns

Abstract

StarDriver was recently proposed as a highly flexible laser driver for inertial confinement fusion and high energy density physics. It envisions a laser drive consisting of many beamlets at an aperture where optical technology is well-developed, and each beamlet has energy ~100 J in a several times diffraction limited beam. Each beamlet has ~1.5THz of 2D SSD smoothing, but the ensemble of lasers has frequency bandwidth 2–10 %, thereby providing significant control of both hydrodynamic and laser-plasma instabilities. In this paper we illustrate the attractive features of the StarDriver concept with detailed calculations of beam smoothing for control of hydrodynamic instabilities in a direct drive ICF target, using a full 3D simulation of the laser drive. We describe here a StarDriver-class laser with 5120 physical beamlets disposed about the target chamber in 80 evenly spaced ports, each port containing 64 beamlets, each beamlet having about ~1.5THz of 2D SSD bandwidth and suitable phase plates, an aperture of ~65 mm, an energy of 80 J, and frequency-converted to ~351 nm. The drive at the target is ~400 kJ, has a well-behaved low L-mode spectrum, and smoothes very rapidly, reaching an asymptotic smoothness of <1 % in less than 1 ns. 2 MJ of drive at the same smoothing performance may be obtained by increasing the number of beamlets. An attractive feature of StarDriver is that the tolerances on the individual beamlet parameters are quite relaxed.