The research into nuclear fusion started around 1920. In that year the physicist F.W. Aston discovered in highly accurate experiments that four hydrogen atoms are heavier than one helium atom. The importance of this discovery was immediately recognised by the brilliant English astrophysicist Sir Edmund Eddington, who realised that the difference in mass meant that the sun was able to burn by converting hydrogen into helium, whereby the difference in mass of 0.7% was converted into energy according to Einstein’s famous relationship between mass and energy, E = mc2. Calculations showed that, in this way, the sun will have enough fuel for billions of years. As early as in 1938, experiments were set up in the US to try and confine a hot plasma using magnetic fields.
Shortly after World War Two there was an international wave of interest in controlling nuclear fusion, and experiments were set up in many countries. As it was thought that the research had military significance, most experiments were secret and there was no international collaboration at the time. This changed in 1958 during the ‘Atoms for Peace’ conference in Geneva. At this conference, many countries including Russia and the US revealed the results of their fusion programmes. They realised that controllable fusion energy was possible, but they also understood that, due to plasma instabilities and other issues, it would not be an easy task.
In order to tackle the technological and scientific issues, in the late 1950s it was decided to organise the research entirely on an international level. In Europe, associations were established between the European Atomic Agency EURATOM and the scientific institutes of the member states. The Rijnhuizen FOM Institute for Plasma Physics was established in the Netherlands in 1958 with the aim to research nuclear fusion.
A breakthrough in nuclear fusion research occurred in 1968 when Russian researchers announced that they had achieved unprecedented results with a tokamak: a special geometry in the shape of a torus. In 1969, still during the cold war, a British team travelled to Moscow and confirmed the results of their Russian colleagues. From that moment on, tokamak experiments were quickly designed and put into operation all over the world.
The current generation of modern, large tokamaks was designed during the 1970s. The Joint European Torus (JET), located near Oxford in England, was put into operation in 1983. Other large tokamaks are located in Germany, France, Japan and the US. In the current generation of tokamaks, fusion plasmas of hundreds of millions of degrees Celsius are routinely generated and maintained for several minutes.
The design of JET, the largest fusion experiment in the world, started in 1973. Construction commenced in 1979 and the experiment was put into operation in 1983. JET was the first tokamak in the world in which real fusion fuel, deuterium and tritium, was used. JET still holds the world record for the generation of fusion energy: in 1997, 16 megawatts were generated during 1 second, and a continuous fusion capacity of 4 MW during 4 seconds. JET is currently a European user facility where hundreds of scientists from Europe, Japan, the US and Russia visit to carry out research .