Stimulated Brillouin scattering pulse compression for excimer inertial fusion energy drivers

摘要

Abstract: A key requirement for the development of commercial fusion power plants utilizing inertial confinement fusion (ICF) as a source of thermonuclear power is the availability of reliable, efficient laser drivers. These laser drivers must be capable of delivering ultra-violet (UV) optical pulses having energies of the order of 5 MJ to cryogenic deuterium-tritium (D/T) ICF targets. Excimer lasers are a leading candidate to fill these demanding ICF driver requirements. However, since excimer lasers are not storage lasers, the excimer laser pulse duration is determined primarily by the length of the excitation pulse delivered to the excimer laser amplifier. Pulsed power associated with efficiently generating excimer laser pulses has a time constant that falls in the range, 30 $tau$-p$/ $LS $tau$-pp$/ $LS 100 $tau$-p$/. As a consequence, pulse compression is needed to convert the long excimer laser pulses to pulses of duration $tau$-p$/. These main ICF driver pulses require longer, lower power precursor pulses delivered to the ICF target before the arrival of the main pulse. Computer simulations have shown that a `chirped,' self-seeded, stimulated Brillouin scattering (SBS) pulse compressor cell using SF$-6$/ at a density, $rho approximately 1 amagat can efficiently compress krypton fluoride laser pulses at $lambda $EQ 248 nm. In order to avoid the generation of output pulses substantially shorter than $tau$-p$/, the optical power in the chirped input SBS `seed' beams was ramped. Compressed pulse conversion efficiencies of up to 68% were calculated for output pulse durations of $tau$-p$/ approximately 6 ns. Techniques for generating a variety of temporally complex output pulse shapes are discussed. !14