The national ignition facility: laser performance status and performance quad results at elevated energy

Abstract

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is the first of its kind megajoule-class laser facility with 192 beams capable of delivering over 1.8 MJ and 500TW of 351 nm light for high accuracy laser-matter interaction experiments. It has been commissioned and operated since 2009 to support a wide range of missions including the study of inertial confinement fusion, high energy density physics, material science, and laboratory astrophysics. In the first section of this paper we discuss the current status of laser performance obtained during the 408 target experiments completed in 2017. The performance spanned a wide range of laser energies, powers and pulse durations as requested for these target experiments. A special emphasis is given on energy delivery and cone power accuracy in the UV, as these are key parameters for successful experiments. In the second section of the paper, the results obtained during the 2017 performance quad campaign are briefly described. During this campaign a series of laser-only shots were taken to perform tests at elevated energies on a single NIF quad. These tests were designed to assess laser performance limits and operational costs against predictive models. This campaign culminated with the delivery of ~54 kJ of UV on a single quad of NIF, and 14 kJ on a single beam aperture, which are both to our knowledge the largest energies achieved to date for a neodymium-glass, frequency tripled architecture.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

“…(e.g., smaller LEHs, interior LEH shields [120,121], lower surface area to volume frustum-shaped "Frustraum" hohlraums [122]) and/or increasing NIF energy [123]. Further research tracks are aimed at improving compression of HDC and hence maximum attainable density and yield [124] by modifying laser pulse and dopant profile [125], using thicker ablators, revisiting high compression CH or other amorphous ablator designs in low gas-fill hohlraums with symmetry control by beam staggering [126] and adding magnetically assisted confinement [127].…”

Silica-Based Sol-Gel Coating with High Transmission at 1053 and 527 nm and Absorption at 351 nm for Frequency-Converting Crystals in High-Power Laser System

“…As for dual-wavelength coating system, the transmission could exceed 99.5% at both 1ω and 2ω, while the transmission at 3ω was about 96%. However, the transmission at 3ω still needs further reduction because about 2-10% of the original 3ω laser energy could be reflected according to different hohlraum structures [16,17], and this energy is yet quite harmful. Since UV curing has been applied for the coatings in high-power laser system [18], the UV PI is considered not only to be able to cure the HRI coating but also to absorb the reflected 3ω laser energy.…”

The importance of the laser pulse-ablator interaction dynamics prior to the ablation plasma phase in inertial confinement fusion studies

“…In order to investigate the interaction at the thermoelastic, melting and ablation regimes, laser fluences from 0.1 to 5.0 J cm −2 are used. Such fluences appear at the very early heating moments of the nanosecond ICF low intensity pulse which illuminates the ablator [45,46]. To monitor permanent damages at later times and to evaluate the ablation depth of the target during the melting and ablation regimes, a white-light interferometric method is implemented accompanying the three-dimensional whole-field method, also based on a Michelson interferometry layout [40].…”