Scientists from South Korea managed to maintain plasma gas at a temperature of 100 million Kelvin for 20 seconds without significant instabilities. This is considered a significant step forward in the search for a sustained nuclear fusion reaction, reports The Register.

Nuclear fusion is a process in which two or more atomic nuclei combine to form a heavier nucleus, releasing large amounts of energy. Despite progress in the field, a sustainable reactor that produces more energy than it consumes is still in the future. One of the barriers was maintaining the stability and temperature of the plasma – the fourth state of matter, consisting of unbound ions or charged atoms.

The Korean Advanced Research Superconducting Tokamak, or KSTAR, operates using hydrogen plasma confined by a magnetic field. However, researchers have not yet been able to achieve stable fusion operation, which requires high temperatures of more than 100 million Kelvin and sufficient instability control to ensure stable operation on the order of tens of seconds. Now researchers at the facility report that they have crossed the threshold.

“Here we report experiments at the Korea Superconducting Tokamak Advanced Research device producing a plasma fusion regime that satisfies most of the above requirements,” the research paper, published in Nature says.

“A low plasma density combined with a moderate input power for operation is key to establishing this regime by preserving a high fraction of fast ions. This regime is rarely subject to disruption and can be sustained reliably even without a sophisticated control, and thus represents a promising path towards commercial fusion reactors,” the authors said.

This year saw other breakthroughs on the way to a sustainable fusion reaction. In January, researchers from National Laser Fusion Facility (NIF) at Lawrence Livermore National Laboratory in California described how they achieved a burning plasma — where the heat from nuclear fusion becomes the primary source of fuel heating — in four experiments, each producing more than 100 kilojoules of energy. The result marked an important step toward nuclear fusion, but it is not true ignition, where a self-sustaining reaction produces more energy than is consumed.

In February, scientists and engineers running the Joint European Torus (JET) facility in Oxford announced a record 59 megajoules of thermal energy from fusion, more than double the previous record, achieved by JET. However, some experts remain ambiguous about the prospects for the commercialization of nuclear fusion as an energy source in the next two to three decades.