Fusion history: an interactive timeline
Why has the road from the first idea of fusion energy to a fusion power plant taken more than a hundred years?
Prior knowledge
- Secrecy, Huemul, ZETA and the Geneva conference of 1958chapter Secret beginnings: fusion research to the 1950s
- The T-3 results and the Culham measurement of 1969chapter Science across the Iron Curtain
- The big machines and the Geneva summit of 1985chapter Big machines and world politics: 1970s to 1985
Core path: follow the steps in order. Tasks marked Optional give extra practice. Optional tasks: 1.
Think about it
In 1920 Arthur Eddington told an audience in Cardiff that the stars shine by turning hydrogen into helium, and that people might one day control this energy. In this chapter you have followed the story through secret laboratories, false claims, a measurement in Moscow and a summit in Geneva. Now you will see the whole road at once, from the first ideas of modern physics to the machines being built today.
What patterns appear when you look at a hundred years of fusion history at once?
Think about it: what do you remember?
Without looking back, write down three events from fusion history that you remember from this chapter, each with its year (a guess is fine) and one word about why it mattered. Then compare with a partner: did you choose the same events?
Sentence starters
- In …, … happened. It mattered because …
- We both chose …
- The most important event was …, because …
Pair work: compare your lists for one minute and agree on the most important event.
Model answer
Geneva, 1958: fusion research was declassified. The Culham measurement of T-3, 1969: independent verification made the tokamak the main design. Reagan and Gorbachev in Geneva, 1985: the rivals agreed to cooperate, which led to ITER.
Assess your own answer
Tick the points your own answer already contains.
Review the theory summary.
Hint 1: a guiding question
Think of one event from the secret years, one from the tokamak race and one from the 1980s.
Predict
Make your predictions before investigating 2 questions
Prediction 1: where does the story happen?
Prediction 2: how long is a step?
Investigate
How to use the timeline
The timeline below tells the whole story of this course in about a hundred events, from the discovery of X-rays in 1895 to the construction of ITER today. Every event is a card. A closed card shows its year, place and title; open it to read a short text, the people involved and the sources it was checked against.
- Eras. The buttons above the timeline choose one of four eras: The birth of modern physics (1895–1938), The nuclear age and secrecy (1938–1958), The tokamak race (1958–1985) and From Geneva to ITER (1985–2026). All eras shows everything.
- Themes. Each event has one theme, shown by a colour and a shape on the year strip: scientific discovery (circle), machines and experiments (square), politics and society (diamond) and people (triangle). The Theme menu shows one theme only.
- Search. The search box finds a word in the titles, texts, names, places and countries, for example Culham, Sakharov or Geneva. The line under the year strip says how many events are shown.
- People and the map. Some cards have a short biography behind Who was …?. When an event is about a machine, Show on the map opens it in the unit Global Fusion Explorer, the world map of fusion facilities.
The events were checked on 1 November 2026. Facts that change, such as ITER's schedule, carry their date. The timeline is a selection, not a complete list of fusion history.
The timeline
Choose an era, a theme or a search word. Click a mark on the year strip to open its card. Some tasks below have their own small timeline with only the events they need.
Exploration sheet
Work in pairs with one device. Do the five tasks below. Tasks 1 and 4 use the big timeline above; Tasks 2, 3 and 5 have their own small timelines with only the events they need. Write your answers on paper or in the boxes, and use the sentence starters when you explain.
Word bank
an era · a theme · an event · a turning point · a claim · to withdraw a claim · to confirm · a trend · a pattern · most / fewest
Sentence starters
- In the era …, the most common theme is …
- Most of the events take place in …
- The claim was checked by …, who found that …
- This event was a turning point, because …
- One pattern we found is …
Task 1: themes by era
The list gives the number of events of each theme in each era. Check one row yourself: choose The tokamak race with the era buttons, then each theme in turn in the Theme menu, and compare the count under the year strip with the list.
- The birth of modern physics (1895–1938), 26 events: science 19 · machines 5 · politics 0 · people 2
- The nuclear age and secrecy (1938–1958), 23 events: science 5 · machines 7 · politics 9 · people 2
- The tokamak race (1958–1985), 15 events: science 4 · machines 8 · politics 3 · people 0
- From Geneva to ITER (1985–2026), 40 events: science 6 · machines 26 · politics 8 · people 0
After the question, discuss with your partner: why might the authors have chosen so many machine records in the last era?
Task 2: three claims and one check
The small timeline below holds only the events of this task: Huemul, ZETA, cold fusion and T-3. Open the cards. For each of the four, write one sentence: what was claimed, who checked it and what they found. Then write one sentence on the difference between the first three and the fourth.
Sentence starters
- In …, … claimed that …
- It was checked by …, who found that …
- Unlike the first three, T-3 …
Pair work: each partner takes two of the four cases, then explain them to each other.
Model answer
Huemul (1951): Perón announced that Richter had produced controlled fusion; Balseiro's team inspected the laboratory in 1952 and found no nuclear reactions. ZETA (1958): British scientists suggested that its neutrons came from fusion; Basil Rose's measurements showed that the neutrons flew mostly in one direction, so they came from accelerated ions, and the claim was withdrawn. Cold fusion (1989): two chemists announced fusion at room temperature; laboratories around the world could not repeat it. T-3 (1968): Soviet scientists reported a temperature of about ten million degrees; the British Culham team measured it with a laser in 1969 and confirmed it. The first three claims were made public before others could check them and failed the check, while T-3 was doubted but passed an independent check.
Assess your own answer
Tick the points your own answer already contains.
Review the theory summary.
Hint 1: a guiding question
Open the cards in the small timeline; most cases have two cards.
Hint 2: what is the connection
For T-3, read both Surprise results at Novosibirsk and The Culham Five confirm T-3.
Task 3: from the timeline to the map
The small timeline below holds the cards of T-3, JET and JT-60. Open them. On each card, use Show on the map, which opens the machine in the unit Global Fusion Explorer. For each machine, note its country (then and now), its site and its status today. Then write two sentences: what do these three machines show about who did fusion research in this era?
Sentence starters
- … was built at … in …
- Today it is … (status, as of …)
- These machines show that in this era …
Pair work: one partner reads the timeline card, the other the map panel.
Model answer
T-3 was at the Kurchatov Institute in Moscow, in the Soviet Union (today Russia); it is no longer operating. JET was at Culham in England, a European project, and it closed at the end of 2023. JT-60 was at Naka in Japan; it was upgraded and rebuilt, and its successor JT-60SA made its first plasma in 2023. The three machines show that in the tokamak race fusion research was led by a few rich powers and groups of countries in Europe, the Soviet Union and Japan, as well as the United States.
Assess your own answer
Tick the points your own answer already contains.
Review the theory summary.
Hint 1: a guiding question
The link is at the end of each card, after the sources.
Hint 2: what is the connection
The map panel shows the status and the date it was checked.
Task 4: turning points
A turning point is an event after which the story goes in a new direction. Choose three events from the timeline that you think were the biggest turning points for fusion research. For each, write its year and one sentence: what changed after it? Then compare your three with another pair and agree on one.
Sentence starters
- … was a turning point, because after it …
- Before …, …; after …, …
- We agreed on …, because …
Group work: two pairs compare their choices and agree on one turning point.
Model answer
1958, Geneva: after the declassification, fusion research changed from secret national programmes to an open international science. 1969, the Culham Five confirm T-3: after this, laboratories everywhere built tokamaks, and the tokamak became the main road to fusion. 1985, Reagan and Gorbachev in Geneva: after this, the Cold War rivals started working together on one machine, which became ITER.
Assess your own answer
Tick the points your own answer already contains.
Review the theory summary.
Hint 1: a guiding question
Look for events after which the next events are of a different kind.
Hint 2: what is the connection
Compare the eras: what event starts each new era?
Task 5a: check Prediction 1
The small timeline below holds only the events since 2015. Open the cards and note the country of each. In the 1950s the timeline's events take place in five countries: the United States, the United Kingdom, the Soviet Union, Argentina (Huemul) and Switzerland (the Geneva conference).
Task 5b: check Prediction 2
The small timeline below holds two cards: the first tokamak and JET's record. Open both and note the years.
Theory summary
What the timeline shows
From open science to secrecy, and back. Until 1938 fusion was open science about the stars. From the discovery of fission to 1958, the nuclear age, politics is the most common theme: bombs, secret programmes and false claims. In 1958 the files were opened at Geneva, and from 1985 the story becomes one of cooperation, which led to ITER.
A wider world. In the 1950s almost all events take place in the United States, Britain and the Soviet Union, with Argentina's false claim and the conference in Switzerland. Since 2015 the events come from seven countries in Europe, North America and Asia (China, France, Germany, Japan, South Korea, the United Kingdom and the United States). Fusion research has spread from a few rival powers to a worldwide network. (The map unit shows many more facilities than the timeline.)
Claims and checks. The Huemul claim (1951), ZETA's neutrons (1958) and cold fusion (1989) were announced before others could check them, and all failed when others checked them. Only ZETA's team withdrew its claim; Huemul was exposed by an inspection, and other laboratories could not repeat cold fusion. The T-3 result (1968) went the other way: it was doubted, then confirmed by an independent measurement in 1969. In every case, checking by others decided.
Slow steps. The first tokamak, T-1, started in 1958. Almost forty years later, in 1997, JET produced $16\ \text{MW}$ of fusion power, still with less fusion power out than heating power in. Each step needed a bigger and more expensive machine, so progress came in decades, not years. From Eddington's idea in 1920 to ITER's planned deuterium–tritium operation in 2039 (the plan as of November 2026) is about 120 years.
Common misconception
"History is a straight line of progress." The timeline shows dead ends (Huemul, ZETA's claim, cold fusion), designs that were put aside and came back (the stellarator, set aside after 1969 and revived in Wendelstein 7-X), and long pauses while big machines were built. A second mistake is to treat a planned date as an event: ITER's dates after 2026 are plans of the ITER Organization, not results.
Back to your predictions
Compare your two predictions with what you found in the timeline. Then answer the opening question in two sentences: why has the road to a fusion power plant taken more than a hundred years?
Would you change your prediction?
Apply
What does each event show?
Find the error
Optional Extension: write your own timeline card
The timeline is a selection. Choose an event from this chapter that is not in it, for example Scylla I at Los Alamos (1958, a theta pinch), T-7, the first superconducting tokamak (1979), or T-15 (1988). Write a card in the style of the timeline: title, year, place and country, a text of three or four sentences, the people involved and at least one reliable source. Your teacher can suggest it for the course timeline.
Sentence starters
- In …, at …, …
- It was the first …
- It mattered because …
- Source: …
Check your understanding
1. Which event ended the secret years?
2. Chronology
3. Using a timeline as a source
4. The chapter's big question
Answer the big question of this chapter in five or six sentences: How did the Cold War influence scientific research? Use at least three events from the timeline, with their years, and say both how the Cold War slowed or distorted fusion research and how it pushed it forward.
Sentence starters
- At first, the Cold War …
- For example, in …
- On the other hand, rivalry also …
- So, the Cold War both … and …
Model answer
The Cold War first made fusion research secret. Around 1950–1951 Britain, the Soviet Union and the United States all started classified programmes, because fusion was linked to the hydrogen bomb and to neutrons for bomb fuel, so scientists could not share or check results. At the same time, rivalry brought money: Perón's false Huemul claim in 1951 helped persuade the United States to fund Spitzer's stellarator. When the plasma problems turned out to be hard for everyone, the files were opened at Geneva in 1958. In 1969 British scientists crossed the Iron Curtain to verify the Soviet T-3 result, which shows that evidence could matter more than politics. Finally, in 1985 Reagan and Gorbachev called for cooperation on fusion, which led to ITER. So the Cold War both slowed fusion with secrecy and pushed it forward with funding and, in the end, with cooperation.
Assess your own answer
Tick the points your own answer already contains.
Review the theory summary.
Hint 1: a guiding question
Think of the three meetings: Geneva 1958, Moscow 1969, Geneva 1985.
Hint 2: what is the connection
What did secrecy prevent? What did rivalry pay for?
Summary
- The timeline has four eras: modern physics (to 1938), the nuclear age and secrecy (1938–1958), the tokamak race (1958–1985) and cooperation from Geneva to ITER (1985–2026).
- Politics dominates the secret years; machines dominate the years of cooperation.
- Fusion research spread from three rival powers in the 1950s to a worldwide network.
- Claims that others could not check (Huemul, ZETA, cold fusion) failed; a doubted result that was independently checked (T-3) changed the field.
- Progress came in steps of decades, because each step needed a bigger machine; as of November 2026, ITER plans deuterium–tritium operation in 2039.
Le coin français
A timeline is une frise chronologique in French: une frise is a long decorated band on a wall. Listen, repeat, and then say the last sentence to your partner.