NATIONAL IGNITION FACILITY Reflector), invented by Sandia National Supporting stockpile Laboratories (SNL) in the 1970s and matured at LLNL for NIF. In 2019, a stewardship through joint LLNL–SNL team successfully commissioned a line-imaging diagnostic a wide range of at Sandia’s Z Pulsed Power Facility, where high magnetic fields and electrical experiments and currents compress targets to HED conditions. Technology transfer of the pursuit of diagnostic was challenging because of space constraints and the Z machine’s fusion ignition, more difficult operating environment. and operating as a PROGRESS IN PURSUING FUSION IGNITION national user facility Achieving fusion ignition and energy gain at NIF is a grand scientific challenge. for high-energy- Significant progress is being made through a combination of data from density science experiments, greatly improved 3D simulations, and machine-learning (ML) NUCLEAR SURVIVABILITY OF COMPONENTS techniques. Using the data from many Target area operators remove a diagnostic assembly with six samples after a target implosion simulations, an LLNL- test. NIF provides a critical capability for testing the survivability of components developed leading-edge ML tool is able from nuclear weapons and other military assets that may face real-world HED SCIENCE EXPERIMENTS to determine the range of simulation nuclear environments. Researchers subject parts, such as electronics, and other National Ignition Facility (NIF) high- input parameters that reproduce the materials to intense doses of x rays and , and in other experiments, they energy-density (HED) science experiments measured results from any selected probe material properties at extreme pressures and . in FY 2019 provided crucial support past experiment. With this information, to the W80-4 life-extension program. scientists have identified principal These tests helped weapons designers barriers to achieving ignition and can evaluate replacement options for aged Engineering technical associates work better gauge uncertainties. Importantly, are combining improvements in the on the Thomson scattering diagnostic DISCOVERY SCIENCE AT NIF materials in the W80 warhead that meet for recording time-resolved spectra. this new capability to fuse experiments, design of the fuel capsule and the Discovery Science experiments at high standards for safety, security, and high-fidelity simulations, and ML helps surrounding hohlraum, proper pulse NIF provide unique opportunities to effectiveness. Such experiments will guide decisions about target design, shaping and beam energy balance, and answer challenging questions about also be vital to the success of the W87-1 future experiments to conduct, and to the extent possible, increased NIF HED science and advance knowledge modification program (see p. 4). Moreover, wide-ranging physical phenomena Ramp compression is important to upgrades to codes and diagnostics. laser energy. The NIF team must also in nuclear physics, physics, HED science experiments at NIF explore central to stockpile stewardship. Many several types of HED materials science reduce hydrodynamic instabilities in materials science, and astrophysics. In tests jointly address challenges arising experiments: equation of state (EOS), 2014 2018 the imploding capsule and the mix of many cases, experiments have required in stockpile modernization, the pursuit x-ray diffraction to study crystalline materials into the fuel’s central hot spot. development of new types of diagnostics of inertial confinement fusion (ICF) structure, and material strength. In To this end, engineers from LLNL and that have become very useful for ignition, and developing a deeper these experiments, x rays from a laser- General Atomics developed and tested national security applications or have led understanding of physics issues pertinent heated holhraum gradually compress a fill tube 2 micrometers in diameter. to significant scientific breakthroughs. to stockpile stewardship. The shots a material sample so that it remains The 10-micrometer-diameter fill tube In FY 2019, LLNL researchers and provide information about the properties relatively cool as it is squeezed to has been a significant source of hot- collaborators published results of of materials at extreme conditions, extreme pressure conditions—up to spot degradation. Engineers are also proton-acceleration experiments in the radiation hydrodynamics and transport, 50 megabars for diamond. Materials exploring ways to produce more uniform journal Physics of Plasmas. Using NIF thermonuclear processes, and material now being tested range from diamond capsules to reduce instabilities and jets and ARC, the team produced beams of mixing. The data are used to improve and and iron (for planetary science) to of materials into the hot spot. As for protons with 10 times more energy than validate 3D simulation models of materials of special interest for stockpile diagnostic improvements, the advanced expected—14 to 18 million . weapons performance. stewardship. In April 2019, researchers Improvements in ICF capsule implosions radiographic capability (ARC) short- Such beams can be precisely targeted conducted the first ramp compression replicated in 3D simulations pulse, high-intensity laser obtained on materials and provide new ways for RAMPING-UP PRESSURE experiment with plutonium-242 (a low- the first radiographic images of an studying extreme states of matter, such ON MATERIALS radioactivity isotope). Scientists are examining ways to imploded fuel and shell. The images as that found in stellar and planetary In FY 2019, Laboratory researchers made For EOS experiments, the principal make high-velocity implosions more confirmed the presence of low-mode interiors. Proton acceleration has A millimeter-size ramp compression target seen significant advances in capabilities to diagnostic is line-imaging VISAR spherical. To better manage problematic asymmetries, which had been inferred potential for many other applications through a cone-shaped perform ramp compression experiments. (Velocity Interferometer System for Any laser–plasma instabilities, researchers from other detectors. in HED science and ICF research. shield

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