Pulsed-power Driven Nuclear Fusion
Early in the history of controlled nuclear fusion research, Lawson demonstrated that fusion reactions can generate net energy when the product of the density (n) and plasma energy confinement time (t) exceeds nt> 10^20 s/m^3, with a temperature of 25 keV. This remarkable result has two profound consequences: firstly, at 25 keV the fusion fuel (typically isotopes of hydrogen) will be in the plasma state, which is very hard to create and confine, and secondly, a huge range of solutions are permitted, from very dense, short-lived plasmas, to very sparse, long-lived plasmas. This wide parameter space has led to a diverse range of fusion reactor concepts, the most successful of which use large, superconducting magnets to confine sparse (n~ 10^20) plasmas for seconds or use intense laser pulses to transiently compress the plasma to very high densities (n~10^30) for fractions of a nanosecond.
These two approaches, respectively called magnetically and inertially confined fusion, both require expensive drivers to reach the required temperatures and densities. Pulsed power offers a third and potentially far cheaper path, in which the application of intense electrical current is used either to Ohmically heat the plasma or to apply intense magnetic pressure to compress it. However, the plasma physics in this intermediate regime is not well understood; instabilities within the plasma, caused by the interaction of the plasma with the magnetic field, hydrodynamic instabilities, or localized runaway cooling, may reduce the plasma lifetime below the value needed for net energy gain. In this talk, I will discuss the role that university-based experiments play in understanding this physics, providing data to test the theories and validate the simulations used to design novel fusion reactor concepts, as well as how developments in pulsed power can lead to new applications for clean energy.
Bio: Jack Hare is an assistant professor in the School of Electrical and Computer Engineering at Cornell University. He studied natural sciences at the University of Cambridge, graduating in 2011, followed by a master’s degree in plasma physics at Princeton University in 2013. His doctoral research on the MAGPIE generator at Imperial College London was supervised by Sergey Lebedev, and he was awarded his Ph.D. in 2017. Following this, he held postdoctoral appointments at Imperial College (2017-2019 and 2020) and the Max Planck Institute for Plasma Physics in Garching, Germany (2019). In 2021, he started a new research group as an assistant professor at MIT, based around the PUFFIN pulsed-power generator, and he moved to Cornell University in 2025. He received the NSF CAREER award in 2023, and the Thomas H. Stix Award for Outstanding Early Career Contributions to Plasma Physics Research in 2025.