LLE Review 87

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Highlights

LLE Review 87, covering April-June 2001, features an article on the 60-beam streak camera system used on the OMEGA laser system. This article (cover and p. 109) describes the system and focuses on the hardware and software calibration techniques that maximize its utility. The system can diagnose each of the beams on every target shot and can measure beam energies with 8% accuracy, and timing at 7 ps rms. Beam-to-beam power variations of less than 5% can be detected.

Additional highlights of research presented in this issue include the following:

• The evolution of shell modulations near the point of peak compression in spherical, direct-drive implosions is examined using both modeling and shot data. The effect of two different levels of beam smoothing is described. Both the model and the experiment show that modulations in the shell areal density decrease during compression and increase during decompression.
• The first multibeam laser-plasma interaction experiments with a critical density surface present at all times are reported. These plasma conditions are tailored to resemble future direct-drive-ignition laser fusion implosions on the NIF. The results show strong evidence of electromagnetic (EM) wave seeding of SBS backscatter as well as evidence of strongly driven, common, symmetrically located ion waves. The expected SBS scattering levels for NIF direct-drive ignition experiments are well below 1%. This gives confidence that good direct-drive target performance will be achieved.
• The main aspects of nonequilibrium hot-electron phenomena in superconducting films are reviewed. Various theoretical models developed to describe the hot-electron effect are presented. The article describes a number of radiation-sensing devices that have been fabricated and tested and demonstrate significantly improved performance over conventional implementations
• The issues associated with determining the minimum drive energy needed to achieve ignition in inertial confinement fusion implosions are explored on a theoretical basis. A new model that consistently incorporates two competitive scaling approaches is developed. Topics covered include hot-spot dynamics, two approaches to shell modeling, derivations of ignition scaling, and verification of initial assumptions. Good agreement with other published results is shown.