John ‘Jack’ Connor is a theoretical physicist whose theories have advanced our understanding of fusion plasmas. This is essential to the development of fusion power, a nuclear technology with the potential to produce cleaner energy on a large scale.

Jack and his colleagues demonstrated that plasma, magnetically confined in a toroidal chamber known as a ‘tokamak’, is able to produce its own current — the ‘bootstrap current’. This allows the steady state operation of a fusion power plant and is now a key element of most modern devices, including the International Thermonuclear Experimental Reactor (ITER). He has also established confinement scaling laws based on plasma physics that help determine how large a tokamak needs to be to produce self-sustaining fusion reactions.

In addition, Jack has developed methods for calculating the stability of a tokamak. This includes the ‘ballooning modes’ that limit the achievable plasma pressure, which is important for the economics of a fusion power plant. Jack was awarded the Hannes Alfven Prize in 2004 and the Payne-Gaposchkin Medal and Prize in 2008.