Akira Hasegawa's Legacy in Laboratory Dipole Physics

Akira Hasegawa peacefully passed away on June 22, 2025, and he is remembered around the world for his many discoveries in plasma physics and nonlinear optics. This poster recounts his time as an adjunct professor at Columbia University and his 1987 proposal to confine a high-temperature plasma by a levitated superconducting dipole magnet [1]. This invention lead to two successful demonstrations of high-pressure plasma confinement: at the Levitated Dipole Experiment (LDX) built jointly by Columbia University and MIT and at the Ring Trap-1 (RT-1) device built at the University of Tokyo. I will recount the science discoveries from the Columbia University "Collisionless Terrella Experiment" and from the Columbia-MIT experiment with a strong levitated dipole, LDX. These experiments established the conditions for chaotic radial transport, nonlinear frequency chirping, the centrifugal interchange instability, inward and outward turbulent transport, and the robust production of high plasma beta with broad profiles characteristic of Hasegawa's 1987 invention. Gratefully acknowledging many colleagues who shared in this research and support from the AFSOR, NSF, and DOE-FES.

[1] A. Hasegawa, "A dipole field fusion reactor." Comments Plasma Physics and Controlled Fusion; 11, no. 3 (1987).