ONE of the nation’s most challenging scientific endeavors of the past two decades has been the National Nuclear Security Administration’s (NNSA’s) Stockpile Stewardship Program, the science-based effort to ensure the safety, security, reliability, and effectiveness of the nation’s nuclear weapons without additional explosive nuclear testing. The program’s outstanding success has been due in large part to the enduring expertise of stockpile stewards at the three NNSA national security laboratories—Lawrence Livermore, Los Alamos, and Sandia national laboratories—in addition to the extraordinary capabilities of high-performance computing and the unsurpassed experimental research facilities maintained by NNSA.
Lawrence Livermore’s National Ignition Facility (NIF), the largest and most energetic laser in the world, is NNSA’s preeminent high-energy-density (HED) stockpile stewardship experimental facility. For a few millionths of a second, NIF’s 192 lasers duplicate the same temperatures, densities, and pressures found in the interiors of stars and planets and detonating nuclear explosives.
Even before NIF began operation in 2010, researchers recognized that in addition to stockpile stewardship, fusion energy research, and national security applications, NIF would be invaluable in advancing fundamental HED science and that a portion of experimental time should be devoted to such research. As a result, Lawrence Livermore launched an experimental research effort that evolved into the Discovery Science Program in 2014. This program enables scientists from academic institutions and government laboratories from within the United States and abroad to perform HED experiments under conditions that only NIF can generate. These experiments include studies of material properties, hydrodynamics, and the interactions of intense radiation fields with matter. As described in the feature article, Laser Experiments Illuminate the Cosmos, the studies have direct applications to disciplines such as astrophysics and planetary physics.
Approximately 8 percent of NIF shots are dedicated to the Discovery Science Program. Thanks to a concerted effort to increase operational efficiency, NIF scientists are currently conducting more than 400 shots a year—more than doubling the annual number of shots from only three years ago. This achievement makes more shots available for Discovery Science experiments than ever.
Competition for time on NIF is keen. Out of 26 proposals received this year, only about 6 will be accepted for shot time in fiscal year 2018. Once a proposal has been accepted, NIF scientists provide feedback on all aspects of the experimental design. Because every experiment is unique, experts in a broad array of fields—including target fabrication, laser configuration, and diagnostics—typically become involved to help guide the researchers. Teams often conduct preparatory experiments at Livermore’s Jupiter Laser Facility or at the Omega laser at the University of Rochester’s Laboratory for Laser Energetics.
NIF’s Discovery Science experimenters bring with them new ideas for experimental techniques, targets, and diagnostics, and their enthusiasm is infectious. Stockpile stewardship scientists at Livermore sometimes join a Discovery Science team, gaining the opportunity to publish their findings in the open literature, strengthen ties with colleagues in academia and other national laboratories, and keep current with the latest scientific discoveries all over the world.
Discovery Science experimenters often include young scientists who are among the best and the brightest researchers of their generation. These talented people are a natural pipeline for future stockpile stewards, and in fact so far about 10 young researchers from Discovery Science projects have been hired by the NNSA national security laboratories. Many other Discovery Science researchers form long-lasting relationships with Livermore colleagues. They can often be found on academic “red teams” charged with evaluating the Laboratory’s scientific findings and experimental approaches.
Lawrence Livermore is excited to be helping grow the international HED community. One important element is the NIF User Group, to which more than 500 scientists around the world belong. In February 2016, the annual NIF User Group meeting took place here, bringing together nearly 180 people from around the world, including 41 graduate students and postdoctoral researchers.
Thanks to NIF, the Laboratory is expertly assessing the nuclear stockpile and re-creating remote parts of the universe with experiments once considered impossible. National security—and fundamental science—are indeed fortunate to have such an extraordinarily powerful and versatile facility.