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Lab Spotlight: DOE - SNOWFLAKE and LEOPARD

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For our energy issue this month, we’ve featured a number of fascinating things that the labs are working on. Here are two more from the Department of Energy, specifically Lawrence Livermore National Laboratory (LLNL).

1. The Snowflake Power Divertor, developed by LLNL researcher Dmitri Ryutov with researchers at Princeton Plasma Physics Laboratory and the Center for Research in Plasma Physics in Switzerland, uses a previously unknown configuration of the divertor magnetic field whose shape is reminiscent of a snowflake. The resulting magnetic field lines spread the exhaust over a larger wall area and reduce the exhaust heat flux to manageable levels. Installing the Snowflake in a newly built fusion facility does not lead to any cost increase. The Snowflake Divertor already has demonstrated large heat-flux reduction in tokamaks in Princeton, N.J., and Lausanne, Switzerland, and will be installed in several facilities under design.

2. LLNL’s Laser Energy Optimization by Precision Adjustments to the Radiant Distribution (LEOPARD) consists of 48 customized “programmable spatial shapers” that have been installed in the preamplifier modules (PAMs) at the front end of the National Ignition Facility (NIF) laser system. At the heart of each spatial shaper is an optically addressable light valve (OALV) that can obscure laser light at programmed locations within the beam profile to prevent the otherwise harsh laser fluence (energy per unit area) from exacerbating small, isolated flaws on downstream optical components. The ability to temporarily "shadow" these isolated flaws from high-fluence laser pulses protects the laser system and enhances operational flexibility. The obscurations that produce the shadows, called “blockers,” are introduced in the PAMs feeding NIF’s beamlines in the laser’s low-fluence, 1,053-nanometer (infrared) region upstream of the main amplifier chain. Imaging and aligning the shadows onto flaws in the output 351-nanometer (ultraviolet) optics ensures that these flaws are protected with only a modest loss of beam area. The LEOPARD system saves an estimated $5 million annually.

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