Japanese-American plasma physicist who led the development of the National Spherical Torus Experiment (NSTX) at Princeton — demonstrating the spherical tokamak as a viable path to compact fusion.
ReviewedLast reviewed: 9 Aug 2026·Category: Scientists & Pioneers
Career
Masahiro Ono is a principal research physicist at Princeton Plasma Physics Laboratory who has been the driving force behind the spherical tokamak program in the United States. He proposed, designed, and led the construction of NSTX, which achieved first plasma in 1999 and became the world’s highest-performance spherical tokamak.[1]
NSTX innovations: Under Ono’s leadership, NSTX demonstrated high beta (plasma pressure vs magnetic pressure) exceeding 40%, coaxial helicity injection for start-up without a central solenoid, and the compatibility of lithium wall conditioning with high-performance plasmas — all critical advances for the compact fusion reactor path.
Contributions
Ono pioneered the concept of using liquid lithium plasma-facing surfaces in spherical tokamaks, demonstrating dramatic improvements in plasma performance. He also contributed to the NSTX-U upgrade, which doubled the magnetic field and plasma current. His work on magnetic reconnection experiments using NSTX has advanced understanding of this fundamental plasma process.[2]
Recognition
Ono is a Fellow of the American Physical Society and has received multiple PPPL Distinguished Research Fellow awards. He has published over 300 papers in fusion science.[3]
Sources
Ono, M. et al. "Exploration of spherical torus physics in the NSTX device." Nuclear Fusion, 40, 557, 2000.
Ono, M. et al. "Liquid lithium loop system to solve challenging technology issues for fusion power plant." Nuclear Fusion, 57, 116056, 2017.