Lawrence Livermore National Laboratory (LLNL) physicists Hye-Sook Park and George Swadling, along with Anna Grassi of France's Sorbonne University and former Lawrence Fellow Frederico Fiuza of Portugal's Técnico Lisboa, received the 2024 Lev D. Landau and Lyman Spitzer Jr. Award for Outstanding Contributions to Plasma Physics.
The award is jointly sponsored by the Plasma Physics Divisions of the American Physical Society and the European Physical Society.
The team was cited for "critical advancement in the understanding of the particle acceleration physics in astrophysically relevant shocks through theoretical analysis and experiments at the National Ignition Facility."
"It is an honor to receive this award," Park said. "We have been studying collisionless shocks in the laboratory using high-power lasers such as NIF and Omega by creating similar conditions in dimensionless units. We were particularly interested in how cosmic ray particles are accelerated to very high energy."
Many theories exist, but observing the exact mechanisms is difficult.
"The physics of collisionless shocks is fascinating," Swadling said. "They are common in astrophysics, forming, for example, at the interface between expanding supernova explosions and the interstellar medium. Only with the laser power and energy available at NIF are we able to design experiments at the spatial and temporal scales required to study their formation in the laboratory."
This work showed that the electrons in the high-velocity plasma gain enough energy through the interplay of self-generated magnetic fields and the shock front, and these electrons are injected into another acceleration mechanism called a first-order Fermi process. The novel diagnostics on NIF measuring particle acceleration and the plasma conditions with novel simulations enabled these findings.
"This project could not have been successful without critical contributions from a broader team of experimental and theoretical physicists, both at LLNL and at a range of international research institutions who have supported this work," Swadling said. "It also is important to recognize the NIF operations and diagnostics teams for their support and guidance in bringing our experiments to fruition."
The experiments on NIF were part of the Discovery Science program, which provides opportunities for a broad range of users to perform high-energy density physics research on the world's most energetic laser. Results of this experimental campaign were previously published in Nature Physics and in The Astrophysical Journal Letters in 2023.
The Landau-Spitzer Award recognizes an individual or group of researchers for outstanding theoretical, experimental or technical contributions in plasma physics and for advancing the collaboration and unity between Europe and the United States by joint research or research that advances knowledge that benefits the two communities in a unique way. The award was presented at the 50th European Physical Society Conference on Plasma Physics, held in July 2024 in Salamanca, Spain.
