Inside a fusion reactor, matter is heated to temperatures hotter than the Sun and confined by powerful magnetic fields. But keeping this superheated plasma stable long enough to produce usable energy remains one of the field’s toughest challenges.

One major problem is that the plasma edge can unleash violent bursts of energy capable of damaging reactor walls, while the exhaust system must also withstand enormous heat loads comparable to those on a spacecraft during reentry.

Now, researchers in China may have found a way to tackle both issues at once.

A team led by Professor Guosheng Xu at the Institute of Plasma Physics, part of the Hefei Institutes of Physical Science under the Chinese Academy of Sciences, has demonstrated a new plasma operating regime on the EAST fusion device that simultaneously reduces heat striking reactor components, suppresses damaging instabilities, and maintains strong energy confinement. The achievement, sustained for roughly a minute in a metal-wall environment, was recently published in Physical Review Letters.

Fusion Challenges: Heat Loads, ELMs, and Stability
Fusion reactors work by confining plasma — an extremely hot, electrically charged gas — inside magnetic fields. For fusion power plants to operate continuously, they must maintain high temperatures and strong confinement while safely removing excess heat and particles from the plasma edge.

One of the most vulnerable regions is the divertor, a specialized exhaust system that handles escaping heat and particles. Under normal conditions, the divertor can experience immense heat fluxes that threaten to erode reactor materials. Scientists often inject small amounts of impurity gases to cool this region through a process called detachment, where the plasma partially separates from the divertor surface. However, excessive cooling can also reduce the plasma’s performance.

Another major issue involves edge-localized modes, or ELMs, sudden eruptions of heat and particles from the plasma edge that behave somewhat like solar flares. These bursts are common in high-confinement, or H-mode, plasmas, which are otherwise desirable because they trap energy efficiently. Eliminating ELMs without sacrificing confinement has long been considered a key hurdle for future fusion reactors.

In the new study, the researchers precisely controlled the injection of light impurity gases inside the EAST tokamak to create what they call the Detached divertor and Turbulence-dominated Pedestal (DTP) regime.