Strengths and weaknesses of KrF lasers for inertial confinement fusion applications learned from the AURORA laser

Abstract

The AURORA KrF laser at Los Alamos became operational in August 1989. AURORA is the first integrated system for demonstrating the capability of a KrF laser to perform target physics experiments for inertial confinement fusion (ICF) and is currently configured as a 5-kJ, 5-ns, 96-beam device. Both laser physics and ICF target physics experiments have been performed over the last year. Of the four major amplifiers in the AURORA laser system, one performed better than expected, one performed about as expected, and two performed below expectations. The causes of the variability in the amplifier performance are now well enough understood that this information can be used to improve the detailed design of the NIKE laser currently under construction at the Naval Research Laboratory. High-dynamic-range pulse shapes have been propagated with minimal distortion through the AURORA amplifier chain, verifying theoretical predictions. Target physics experiments have been performed with intensities greater than 100 TW/cm 2 , pulse lengths ranging from 2-7 ns, and sp<">t-size diameters from 500-1100 /xm. The analysis of this first-generation kjclass KrF laser target physics facility identified the strengths and weaknesses of KrF lasers for ICF applications. Detailed measurements of amplifier performance led to a better understanding of issues for KrF laser-fusion systems, and design studies for future KrF lasers for ICF applications incorporate improvements based in part on AURORA experience.

GARPUN-MTW: A hybrid Ti:Sapphire/KrF laser facility for simultaneous amplification of subpicosecond/nanosecond pulses relevant to fast-ignition ICF concept

“…laser-plasma interaction during the past two decades at 0.1-10.0 kJ-class single-shot KrF facilities AURORA (Los Alamos National Laboratory; LANL) (Rosocha et al, 1986(Rosocha et al, , 1987Harris et al, 1993), NIKE Naval Research Laboratory (NRL) (Obenschain et al, 1996;Pawley et al, 1997Pawley et al, , 1999Aglitskiy et al, 2002), SPRITE (RAL) National Institute of Advanced Industrial Science and Technology (Shaw et al, 1993(Shaw et al, , 1999Divall et al, 1996), ASHURA National Institute of Advanced Industrial Science and Technology (AIS & T) (Owadano et al, 1989(Owadano et al, , 1993(Owadano et al, , 1999(Owadano et al, , 2001 and GARPUN Lebedev Physical Institute (LPI) (Basov et al, 1993;Zvorykin & Lebo, 1999;Zvorykin et al, 2001Zvorykin et al, , 2004Zvorykin et al, , 2006aWang et al, 2002), and especially at rep-rate Electra laser (NRL) (Sethian et al, 1998Wolford et al, 2006) have proved that e-beam-pumped KrF laser might be the best challenge for direct-drive ICF power plant. To satisfy physical and economical requirements, they should be scaled to output energies of 30-60 kJ per one module, operating all together with the total laser energy of $2 MJ at rep-rate of 5 Hz and overall system efficiency of 7.5% (Svyatoslavsky et al, 1992;Von Rosenberg, 1992;McGeoch et al, 1997;Sethian et al, 2003).…”