Tiny parts and absolute meticulousness define Suhas Bhandarkar's award-winning 20-year career at Lawrence Livermore National Laboratory (LLNL). As group leader for Target Fabrication Science and Technology (S&T), he leads a team that helps transform LLNL's physicists' bold ideas into reality at the National Ignition Facility (NIF).
Bhandarkar's path began with a B.S. and Ph.D. in chemical engineering from the University of Rhode Island, followed by a decade at Bell Labs working in optical materials. In 2006, LLNL brought him on board for his expertise in photonics and fiber optics - but target fabrication quickly became his calling.
"When I arrived, the need of the hour was in targets," he said. "So that was where I ended up, and I've never left."
Target fabrication stands among the Seven Wonders of NIF, the technological achievements that made the one-of-a-kind facility possible. At the heart of inertial confinement fusion (ICF) experiments is a tiny fuel capsule, suspended inside a hohlraum that receives the energy of 192 lasers. The goal is to implode the capsule, causing the deuterium-tritium fuel to fuse and ignite. Continued advances in target fabrication are essential to the repeated achievement of fusion ignition on NIF.
These targets face extreme temperatures and pressures, so they require flawless design, fabrication, assembly and materials. The scale is astonishing, especially in contrast to the three-football-field size of NIF. The fuel capsule measures just 2 millimeters across and the hohlraum about 9 millimeters long and 5 millimeters wide, no bigger than a pencil eraser.
"When I joined, target fabrication as we now know it was just starting with one person making about four ICF targets a year, each of which did not quite cross the finish line due to a combination of difficult challenges," said Bhandarkar. "Today, we produce well over 350 targets each year with a 95% success rate."
As the Target Fabrication team grew, they pioneered new manufacturing and evaluation techniques for target assemblies with dozens of intricate parts and built the infrastructure needed for success. They partnered with Diamond Materials in Germany for the fuel capsule shells and strengthened collaboration with General Atomics in San Diego on characterization and component manufacturing.
"The tolerances on NIF targets are near-impossibly high," Bhandarkar said. "Coming from industry, it seemed like mission impossible. But if you put your mind to it and do the work, you can solve these problems."
Precision is everything. Components must be machined to within microns or better. For scale, a human hair is about 80 microns in diameter. Many features are well under 100 nanometers, which is 0.1 microns.
Inside these boundaries, Target Fabrication S&T keeps innovating to improve implosion quality and deepen understanding of the physics involved. Experimental physicists bring the ideas; Bhandarkar's team helps bring them to fruition.
"The starting point continues to be, well it's not impossible," said Bhandarkar.
From that spark, the team tackles feasibility and execution, sometimes over years of dedicated effort - often with big results.
About a decade ago, Target Fabrication S&T created a cryogenically frozen fuel layer about 15 microns thick, over three times thinner than the typical 65-micron layer. This breakthrough enabled better study of the fuel and ice layer mixing during implosions, leading to crucial improvements.
Another challenge was the tiny fill tube used to inject fuel into the capsule, with the associated hole in the capsule wall also serving to leach out the mandrel material. Despite being only 10 microns in diameter, it left a footprint on the capsule surface that caused asymmetry in implosions. Working with General Atomics, the team shrank the fill tube to just 2 microns with a precisely designed shape.
Other projects have included improving the depleted uranium lining on hohlraums and creating foams on interior walls of the hohlraum. Most recently, fine-tuning the fuel capsule's outer layers has helped several experiments achieve ignition.
Bhandarkar credits his team's success, in part, to their diversity of experience and expertise.
"We've got physicists, chemists, materials scientists and mechanical engineers," he said. "Target Fabrication S&T draws from all of these areas. It takes a well-rounded, collaborative team."
In 2024, Bhandarkar received the Larry Foreman Award for innovation and excellence in ICF target fabrication. The award was named in memory of the late Larry Foreman, a renowned Los Alamos National Laboratory fusion physicist who was also an Edward Teller Award recipient. Previous LLNL recipients include Steve Letts, Masaru Takagi, Russell Wallace, Robert Cook, Carlos Castro and Abbas Nikroo.
"I am honored to receive this award. I think it's really a testament to this group," he said. "I'm so grateful for the opportunity afforded by the Lab to sustain these projects, enabling teams to work on hard problems over years and solve complex problems. And we can see that effort paid off with achieving and repeating ignition. That success is the ultimate reward."
