Big Ideas Lab podcast zooms in on tiny targets

At the end of an inertial confinement fusion (ICF) experiment at Lawrence Livermore National Laboratory’s National Ignition Facility (NIF), the target, measuring just two centimeters, is mostly obliterated. The gold plating, the high-density carbon and months of meticulous assembly vanish in an instant.

That’s the point. In that flash, the target becomes what NIF is built to produce: experimental data that helps ensure the safety, security and effectiveness of the nation’s nuclear deterrent and deepens our understanding of high-energy-density physics.

The latest episode of the Big Ideas Lab podcast focuses on these tiny targets: marvels of design, engineering and precision manufacturing that are no bigger than a pencil eraser. Follow one from its start as a high-density carbon shell right to its final destination in the NIF Target Chamber. Listen on Apple or Spotify.

“It has to be as perfect as possible,” LLNL target fabrication program manager Michael Stadermann said.

Targets consist of a fuel capsule just 2 millimeters across — much smaller than a peppercorn — suspended inside a tiny, gold-plated cylinder called a hohlraum. The parts that hold it all together are machined to within an accuracy of 1 micron, with sub-microscopic features no larger than 100 nanometers. For perspective, a human hair is about 80 microns or 80,000 nanometers, wide.

These ICF targets are so specialized that fabrication begins in Germany, continues at General Atomics in San Diego and finishes at LLNL. Along the way, technicians scrutinize every fuel capsule to make sure it meets NIF’s standards. A divot smaller than a bacterium can be enough to render a capsule unusable. That characterization also strengthens the science, giving experimental physicists the detailed measurements they need to interpret results.

“We basically create a Google Earth of the entire capsule. We zoom in on any defect or feature and provide a histogram to the physicists,” said Jared Hund, General Atomics’ LLNL contract manager.

While ignition targets draw the most attention, NIF uses many target designs, tailored in shape and materials to each experiment. Some targets don’t even contain fuel. Manufacturing processes also differ — for some targets, the work all happens in Livermore. But every NIF target is a science and engineering wonder.

Listen to the episode on Apple or Spotify.