Lowering fusion ignition temperature using turbulent flows

Nuclear fusion requires subjecting fuel to extreme temperatures and pressures to reach a critical point. When exploring the potential of sustained fusion as a source of power generation, one challenge is generating the ignition condition as efficiently as possible.

Henry Fetsch and Nathaniel Fisch had previously discovered that, counterintuitively, certain shear flows could increase the fusion reactivity of hot plasma.

“Contrary to the standard picture, where the temperature of a plasma is the only thing that affects fusion reactivity, we realized that fast ions — the ones that are actually responsible for fusion reactions — care not just about the thermal temperature but also about the flows in the plasma,” said Fetsch.

This time, the duo generalized the longstanding fundamental ignition condition in inertial confinement fusion, showing how new ignition regimes are in fact possible by driving small-scale turbulence.

The researchers employed analytical calculations to demonstrate that inducing small-scale, internal turbulent flows inside the plasma can not only lower ignition temperature but reduce the overall input energy needed to reach ignition. This is true even when factoring in the thermal energy in the plasma that is replaced with turbulent kinetic energy.

Having illustrated the theoretical underpinnings of their idea, the duo are now looking to develop strategies to induce turbulence in fusion devices while avoiding turbulent mixing that introduces impurities and degrades plasma confinement.

“We now know what kind of flows we would like to get and when we would like to get them,” said Fisch. “Now, the trick is to engineer the scales that we want at the time that we want.”

Source: “An ignition criterion for inertial fusion boosted by microturbulence,” by Henry Fetsch and Nathaniel J. Fisch, Physics of Plasmas (2026). The article can be accessed at https://doi.org/10.1063/5.0295335 .