On February 12, 2025, the WEST tokamak at the CEA (Commissariat à l’énergie atomique et aux énergies alternatives) facility in Cadarache, southern France, sustained a plasma at 50 million degrees Celsius for 1,337 seconds — 22 minutes and 17 seconds. It is the new world record for plasma duration in a fusion reactor, achieved with a heating power of just 2 megawatts.
The previous record had stood for less than a month. On January 20, 2025, China’s EAST tokamak — the Experimental Advanced Superconducting Tokamak — had clocked 1,066 seconds, or 17 minutes and 46 seconds, at temperatures exceeding 100 million degrees Celsius — six times the temperature at the Sun’s core. That result had already more than doubled EAST’s own previous record of 403 seconds, set in 2023. The progression is nearly exponential: from 403 to 1,066, then to 1,337 seconds within thirteen months. WEST improved on the Chinese benchmark by 25%.
The two experiments measure different aspects of the same challenge. EAST pushed for extreme temperatures — above 100 million degrees — in high-confinement mode, the operating regime that commercial reactors will need to replicate. WEST demonstrated that a plasma can remain stable over extended periods without the reactor’s internal surfaces eroding or becoming contaminated. Keeping a fusion reaction alive is not just a matter of heat: it is a matter of sustained stability. Song Yuntao, director of the Institute of Plasma Physics at the Chinese Academy of Sciences, has set the bar plainly: a fusion reactor must operate stably for thousands of seconds for the plasma to circulate autonomously. One thousand seconds, then, is the floor, not the ceiling.
Both results feed directly into ITER, the international experimental reactor under construction at Cadarache. Data gathered by WEST will inform the operational playbook for ITER’s first plasma cycles. China has been an ITER partner since 2006, contributing 9% of construction and operational costs, and EAST serves as a testbed for the technologies ITER will rely on. In 2024, ITER reached 100% of its construction targets; in April 2025, the first vacuum vessel sector module was lowered into the tokamak pit, three weeks ahead of schedule. The current timeline calls for deuterium-deuterium plasma operations beginning in 2035 and deuterium-tritium operations from 2039. Upcoming WEST campaigns will aim for sessions that cumulatively accumulate several hours of plasma time, with temperatures rising progressively.
What is unfolding is a productive global competition among laboratories: every new record raises the ambition of the entire field. China, in July 2025, launched China Fusion Energy, a state-owned company capitalised at $2.1 billion, with the goal of bringing the China Fusion Engineering Test Reactor online by the end of the decade. On the private side, more than 77 startups worldwide have collectively raised $15 billion. The question is no longer whether fusion works — it does, and the numbers prove it. The question is how quickly plasma seconds will translate into kilowatt-hours on the grid.
