New College DPhil student wins American Physical Society’s top thesis prize for fusion plasma research

Richard Nies, a DPhil student at New College, has been awarded the American Physical Society’s 2026 Marshall N. Rosenbluth Outstanding Doctoral Thesis Award for research on how turbulence behaves inside fusion reactors.

Nuclear fusion, the process that powers the Sun, requires fuel heated to temperatures over a hundred million degrees. Reaching those temperatures in a reactor is difficult because turbulent mixing carry heat away. Turbulent swirls, just as they mix milk and coffee together, also mix the hot plasma core with the cold plasma edge. Controlling this turbulence is essential to developing fusion energy.

Richard’s thesis, Turbulence and flows in toroidal fusion plasmas, examines the two leading  reactor designs: the symmetric doughnut-shaped tokamak and the three-dimensional, “twisty” stellarator. Combining pen-and-paper theory with numerical simulations, he showed that the curvature of the doughnut causes turbulence-generated flows to travel across the plasma. These flows play a central role in setting how strong the turbulence becomes, and therefore how much heat it carries away.

“It is a great honour to have my thesis recognised by the American Physical Society,” Richard reflected. “Marshall Rosenbluth, often called ‘the pope of plasma physics’, shaped so much of the field that it is particularly meaningful to receive a prize in his name.”

He paid tribute to his adviser, Prof. Felix Parra Diaz, formerly of Oxford, who won the same prize in 2011. “I couldn’t have wished for a better adviser,” he said, “in whose footsteps I now gladly follow.”

Richard is now exploring whether the travelling flows could explain “turbulent avalanches” seen in simulations and experiments for decades, although more research is needed to confirm this. He is also studying turbulence in other regimes. “In the longer term, my goal is to reach a deeper understanding of plasma turbulence, and to leverage this understanding to help bring about fusion energy.”