The US federal office that funds and directs the nation's fusion energy research — supporting both foundational plasma science and the push toward a fusion pilot plant.
The Office of Fusion Energy Sciences (FES) is a program office within the US Department of Energy's Office of Science. It is the primary federal agency responsible for funding magnetic and inertial confinement fusion research, plasma science, and enabling technologies in the United States. FES supports research at national laboratories, universities, and through public-private partnerships aimed at making fusion energy practical.[1]
FES has a dual mission: advancing the fundamental understanding of plasma — the fourth state of matter — and developing the science and technology needed to deliver fusion as an energy source. Its portfolio spans burning plasma physics, materials science under extreme neutron environments, fusion nuclear science, advanced computing for plasma simulation, and the development of next-generation confinement concepts.[2]
FES funds and oversees major experimental facilities including DIII-D at General Atomics (the largest operating tokamak in the US), the National Spherical Torus Experiment Upgrade (NSTX-U) at Princeton Plasma Physics Laboratory, and numerous smaller devices at universities across the country. It also supports the US contribution to ITER, managed through a dedicated US ITER Project Office at Oak Ridge National Laboratory.[1]
In recent years, FES has expanded its focus to include public-private partnerships with the growing commercial fusion sector. The Milestone-Based Fusion Development Program, launched in 2022, provides cost-shared funding to private fusion companies to accelerate the path toward a pilot plant. Initial awards went to companies pursuing both magnetic and inertial confinement approaches.[3]
The 2020 report of the National Academies, "Bringing Fusion to the U.S. Grid," recommended that the US pursue a fusion pilot plant producing net electricity by the 2040s. FES has adopted this goal as a guiding objective, reorienting its programs to emphasize technologies needed for a pilot plant, including advanced magnets, materials that can withstand fusion neutron damage, tritium fuel cycle systems, and integrated plasma scenarios compatible with power plant requirements.[2]
Beyond energy applications, FES supports fundamental plasma science research relevant to astrophysics, space weather, advanced manufacturing, and national security. This basic science portfolio, while smaller than the fusion energy component, has produced foundational advances in understanding turbulence, magnetic reconnection, and plasma self-organization that benefit the broader scientific community.