“I attribute our success to an innovative, diverse team of scientists that share their varied technical backgrounds to solve a highly multi-disciplinary challenge.”
—Materials scientist Michael Bagge-Hansen
As the pursuit of fusion ignition and other research continues on NIF, LLNL researchers are conducting increasingly challenging experiments. And a key to the success of these experiments is the hard work and dedication of the talented members of the NIF Target Fabrication Team. Their expertise in developing and refining intricate, precisely fabricated targets that meet the researchers’ needs has made a vital contribution to NIF’s progress over the last 10-plus years.
While some target designs can be used more than once, the majority must continually be revamped in response to experimental results and ever-more sophisticated diagnostics. Targets designed for inertial confinement fusion (ICF) and high energy density (HED) experiments, for example, include a variety of hohlraum shapes, sizes, and linings as well as target capsule materials ranging from plastic to beryllium and high-density carbon, or diamond.
“The team really comes together to work through challenges and meet new requirements. We have a fun team environment and the work is never boring.”
—Becky Butlin, Target Fabrication interface manager
Targets for the wide range of NIF experiments, such as ICF, equation of state, complex hydrodynamics, and radiation transport, provide information on such things as shock timing, capsule implosion shape, implosion velocity, and the extent to which the colder deuterium-tritium fuel in the capsule mixes with the hot spot in the core. For example, to reduce implosion instabilities, researchers are investigating several different methods of suspending the target capsule inside the hohlraum and decreasing the size of micro-thin fill tubes used to inject fusion fuel into the capsule.
NIF targets are marvels of design and manufacturing precision; some components must be machined to an accuracy of one micron with surface features no larger than approximately 10 nanometers. The Target Fabrication Team has developed a number of new measurement instruments and metrology techniques to help ensure the highest standards of quality and precision are met.
Following the example of the automobile industry and other mass-production facilities, the team uses robotics and automated systems to reduce assembly effort hours on time-consuming processes.
These and other efficiency improvements reduced the average fabrication time for cryogenic targets from almost 100 hours per target in 2013 to 83 hours at the beginning of 2015. By the end of 2016, that average was down to 55 hours.
Despite the challenges of designing, manufacturing, and testing a constant stream of these complex targets, the Target Fabrication Team and its partners at General Atomics, Gryphon Schafer, Los Alamos National Laboratory, and the UK’s Atomic Weapons Establishment have consistently increased production to keep pace with NIF’s steadily rising shot rate.
“Scientists Encouraged by Initial Frustraum Experiments at NIF,” NIF & Photon Science News, July 29, 2020
“Focusing Targets Give Over 10x Performance Boost to NIF’s ARC,” NIF & Photon Science News, February 12, 2020
“Bobbing Shells Key to Future NIF Targets,” NIF & Photon Science News, March 20, 2019
“Big Ideas for Tiny Targets,” Science & Technology Review, March, 2018
“Target Fab’s ‘Fantastic 42’ Process Improvements,” NIF & Photon Science News, July, 2017
“A Growing Family of Targets for the National Ignition Facility,” Science & Technology Review, January-February, 2016
“Target Fabrication Steps Up to the Challenges,” NIF & Photon Science News, July, 2015
Next Up: Diagnostics