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In this talk, I will describe a series of experiments carried out over the last decade to study magnetic reconnection. Reconnection is a ubiquitous process throughout the Universe, in which sheared magnetic field lines come together within a plasma, generating an intense sheet of electrical current which breaks the frozen-in condition of ideal magneto-hydrodynamics. Within this current sheet (or reconnection layer), magnetic field lines change their topology and reconnection, and magnetic energy is dissipated in the form of heat, fast outflows, and energetic particles.
Reconnection has been extensively studied in theory, simulations, astronomical observations, by in-situ spacecraft and in the laboratory. Pulsed-power-driven experiments heat initially solid wires to produce hot [10 eV], dense [10^18 cm^-3], fast-moving [50 km/s] plasma flows with embedded magnetic fields [3 T] on centimeter scales, in a beta ~ 1 regime which complements other experiments.
The first of these experiments studied anti-parallel reconnection with different plasma compositions. Aluminium plasmas led to rapid radiative cooling at relatively low Lundquist numbers, whereas carbon plasmas produced plasmoids within the reconnection layer, associated with anomalously fast heating. More recently, we have explored guide-field reconnection, and observed quadrupolar density structures associated with two-fluid effects.
I will also discuss experiments scaled to use the Z Machine at Sandia National laboratories, the world's largest pulsed-power generator. In these experiments, we were able to produce plasmoids in a reconnection layer undergoing strong radiative cooling. We observed that the X-ray emission was localised to the plasmoids, which were rapidly extinguished as they radiatively cooled.
Prof. Jack Hare is an assistant professor in the Cornell School of Electrical and Computer Engineering. He graduated with First Class honours in Natural Sciences at the University of Cambridge in 2011, followed by a Master’s degree in Plasma Physics from Princeton University in 2013. His doctoral research on the MAGPIE generator at Imperial College London was supervised by Prof. Sergey Lebedev, and he was awarded his PhD 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 APS Thomas Stix Award in 2025.
