Jason Parisi is a Principal Scientist at Marathon Fusion, where he develops the science and technology needed to scale nuclear fusion from today’s systems to terawatt capacity. A theoretical physicist, his work spans plasma physics, neutronics, fusion neutron-driven transmutation, and tritium fuel cycle. His core thesis is that fusion neutrons are a transformative resource, enabling isotope production, new energy-conversion pathways, and early revenue streams that accelerate commercialization. Prior to Marathon, he held research roles at Princeton Plasma Physics Laboratory and the Culham Centre for Fusion Energy. Jason holds a PhD from Oxford and a BS from Yale.