France's WEST tokamak holds a plasma for 22 minutes, a duration record

CADARACHE, France, February 2025 — CEA's WEST tokamak held a hydrogen plasma for 1,337 seconds, about 22 minutes, on Feb. 12, 2025, beating the tokamak record for plasma duration. Here's what happened, what it cost, and what went wrong.

Cost and outcome (as of February 18, 2025)

Outcome: 1,337 seconds of plasma, a 25% improvement on the previous record set by China's EAST a few weeks earlier. (CEA)
Inputs: 2 MW of heating from a single antenna; 2.6 GJ of energy injected and extracted. (CEA-IRFM)
Temperature: 50 million degrees. (CEA)
Cost: not stated by CEA.
Status: an experimental plasma, with no fusion power produced or claimed.

How the shot went

The two days of experiments, Feb. 12 and 13, aimed to exceed 1,000 seconds, one of WEST's main goals. The campaign that ended in December 2024 had already reached 824 seconds. (CEA-IRFM)

On Feb. 12, a first hydrogen plasma ran 819 seconds. The next, plasma number 61299, ran 1,337 seconds. Heating power was adjusted in real time to hold a plasma current of 215 kA. (CEA-IRFM)

It wasn't flawless. Around 1,040 seconds, one of the seven klystrons powering the heating antenna stopped, and the plasma "reorganized into a new regime" until the heating system stopped at second 1,337, ending the shot. CEA said much of the data is still being analysed. (CEA-IRFM)

The next day, focused on deuterium, the best plasma lasted 921 seconds. (CEA-IRFM)

Why duration matters

CEA says durations like this are a crucial milestone for ITER, which will have to hold fusion plasmas for several minutes. The goal is to control a naturally unstable plasma while the components facing it survive its radiation without failing or polluting it. (CEA)

"WEST has achieved a new key technological milestone by maintaining hydrogen plasma for more than twenty minutes through the injection of 2 MW of heating power," said Anne-Isabelle Etienvre, CEA's director of fundamental research. (CEA)

What it took to control

Plasma density was controlled by injecting hydrogen through piezoelectric microvalves. CEA-IRFM says plasmas this long need real-time control systems that can react to events in the plasma and in the components facing it, "including unexpected overheating." (CEA-IRFM)

WEST hosts researchers from around the world, CEA says, drawn by the superconducting coils and actively cooled components that allow long plasmas. CEA counts it alongside JET, Japan's JT-60SA, China's EAST, South Korea's KSTAR and ITER. (CEA)

What comes next

CEA-IRFM wants to raise heating power from 2 MW to 10 MW, still over roughly 1,000 seconds, which it says corresponds to fusion power on the order of a gigawatt in an ITER-sized machine. That would test how long the tungsten components last. (CEA-IRFM) CEA also said it would aim for very long plasmas, "up to several hours combined." (CEA)

The record context

CEA notes that JET in the UK, closed in late 2023, holds the record for fusion energy, and that JET showed fusion power of 15 MW for several seconds. WEST's record is for duration, not energy. (CEA)

What went wrong

No fusion power. The record is for holding a plasma, not producing fusion energy; CEA doesn't claim any.
A heating fault mid-shot. One of seven klystrons failed around 1,040 seconds. (CEA-IRFM)
CEA's own caution. CEA says it is "unlikely that fusion technology will make a significant contribution to achieving net-zero carbon emissions by 2050," and that economic feasibility "must still be demonstrated." (CEA)
What we don't know yet: the cost of the campaign, and whether the record has since been beaten.

Our follow-up question for CEA

Has WEST since run at higher heating power over 1,000 seconds, and what did it show about tungsten component lifetime?

Sources

CEA, “Nuclear fusion: WEST beats the world record for plasma duration!,” Feb. 18, 2025. cea.fr
CEA-IRFM, “WEST sets a new plasma duration record,” February 2025. irfm.cea.fr

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