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Fusion milestones: what has happened and what is promised

The milestones that mark progress towards fusion power, which have been reached and when, and what fusion organisations say they will do next, in their own words.

Guide · Updated

Fusion announcements use a handful of words, such as “breakeven”, “ignition” and “net energy”, that sound like one milestone but can mean several. This guide sets out the steps in order, says which have been reached, with device and date, and then lists what organisations say comes next. Everything in the final section is a claim by the organisation named, not a result.

The milestones in order

1. First plasma. A new machine makes its first plasma. It shows the machine works, not that it performs. JET’s first experimental campaign began on 25 June 1983.

2. Fusion in deuterium-tritium fuel at scale. Running the real power-plant fuel, with the tritium handling and neutron shielding that requires. Done by TFTR in the United States and JET in the United Kingdom in the 1990s, and by JET again in 2021 and 2023.

3. Scientific breakeven. Fusion energy out exceeds the energy delivered to the fuel: a target gain above 1 for laser fusion, a plasma gain above 1 for magnetic fusion. Reached for laser fusion in December 2022. Not yet reached for magnetic fusion.

4. Ignition. The fusion reactions heat the fuel enough to keep themselves going. The word is used in more than one sense. Lawrence Livermore National Laboratory defines it physically, as the point where heating by the fusion reactions’ own alpha particles “overcomes the cooling effects of x-ray losses, electron conduction, and implosion expansion”, and says NIF reached it in December 2022. The US Department of Energy’s announcement of that shot used a simpler test, “more energy from fusion than the laser energy used to drive it”, which is the same as scientific breakeven for laser fusion. In magnetic fusion, ignition means a plasma that needs no external heating at all; no magnetic device has reached it.

5. Engineering breakeven. The whole plant produces more electricity than it consumes, including everything it uses to run itself. This is engineering gain above 1. Not reached. No fusion device has yet produced any electricity, so every device’s engineering gain is zero.

6. Net electricity to the grid. A plant exports electricity for sale, reliably. Not reached.

7. Commercial operation. A plant runs for years at a cost buyers will pay. Not reached.

The fusion gain guide explains why steps 3 and 5 are so far apart: NIF’s first target gain of 1.5 came from a shot for which the facility stored about 400 MJ of electricity, a wall-plug gain of about 0.0078 at most.

Results to date

Each item below is in the dataset, and links to the device. The full list, year by year, is on the timeline.

1994. TFTR reaches a plasma gain of 0.28 with deuterium-tritium fuel (shot 76778, 27 May).

1995. TFTR records a triple product of 7.9 × 10²⁰ keV·s·m⁻³ (shot 83546, 17 February), still the highest measured value for a magnetic-confinement device in the dataset. It is about a quarter of the level needed for ignition.

1997. The Joint European Torus reaches a plasma gain of 0.63 (shot 42976, 31 October). It remains the highest plasma gain in the dataset.

2021. JET releases 59 MJ of fusion energy in a single pulse (pulse 99971, 21 December).

2022. The National Ignition Facility reaches a target gain of 1.5: 3.1 MJ of fusion energy from 2.05 MJ of laser light (shot N221204, 5 December). The first target gain above 1, and the only shot in the dataset whose results are held as achieved.

2023. Wendelstein 7-X runs a plasma for 480 seconds (15 February). EAST holds a high-confinement plasma for 403 seconds. JET releases 69.26 MJ in one pulse over five to six seconds (pulse 104522, 3 October), the largest single-pulse fusion energy in the dataset, and ends operation on 18 December with pulse 105842.

December 2023 to February 2024. KSTAR in Korea sustains ion temperatures of 100 million degrees (about 8.6 keV) for 48 seconds. The Korea Institute of Fusion Energy said the same campaign held high-confinement mode for 102 seconds; the dataset does not hold that figure as a separate record. A separate report of 102 seconds at 100 million degrees in 2026 is held as disputed.

2025. EAST sustains a high-confinement plasma for 1,066 seconds (20 January). WEST in France holds a hydrogen plasma for 1,337 seconds (12 February), the longest plasma in the dataset; the record does not state its confinement mode. NIF reaches a target gain of 4.13 with 8.6 MJ of fusion energy (shot N250406, 7 April).

Two things stand out. First, every measured gain above 1 has come from laser fusion, and none from magnetic confinement, whose best plasma gain is still 0.63 from 1997. JT-60U’s often-quoted gain of 1.25 from 1998 is an equivalent gain: a calculation of what a deuterium plasma would have done with D-T fuel. Second, records in energy and duration have kept coming while magnetic-confinement gain has not risen: JET’s 2023 energy record came at a scientific gain of 0.37, according to the Wurzel and Hsu compilation.

What organisations say comes next

These are the organisations’ own statements. The benchmark holds a target as planned, never as achieved, and keeps it off every leaderboard. Where an earlier promise has fallen due, that is noted. Named plants and the one dated purchase of fusion electricity are in the commercial timeline of fusion power.

Commonwealth Fusion Systems says its SPARC tokamak, under construction, will in 2027 “produce more energy from fusion than it needs to power the process”, which it calls Q > 1. The peer-reviewed SPARC design overview (2020) sets the mission as a plasma gain above 2, with a projection of about 11 under nominal assumptions. CFS says a successor plant, ARC, will “put power on the grid”. See Commonwealth Fusion Systems.

Helion Energy announced on 10 May 2023 an agreement to supply Microsoft with electricity from a fusion plant “expected to be online by 2028”, delivering “50 MW or greater after a 1-year ramp up period”. The same announcement said its seventh prototype was “expected to demonstrate the ability to produce electricity in 2024”. That date has passed, and the dataset holds no measurement of electricity from any Helion machine. In February 2026 Helion said that prototype, Polaris, had produced measurable D-T fusion. See Helion Energy.

ITER, the international tokamak under construction in France, is designed to produce 500 MW of fusion power from 50 MW of heating, a plasma gain of 10. Under the baseline schedule presented in 2024, research operation starts in 2034, operation at full magnetic energy follows in 2036, and deuterium-tritium operation begins in 2039. The previous schedule had deuterium-tritium operation four years earlier. See ITER.

How the benchmark treats dates

A result enters the dataset with the date of the shot, not the press release. KSTAR’s 48-second result, for example, is dated to its campaign ending in February 2024, not to the announcement in March 2024. A date in the future is a plan. A plan that passes its date without a result stays in the record, because records are never deleted to tidy up a missed date.

Sources

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