During Heritage Open Weekend there was an exhibition upstairs in Unit 25 Bury Street about 60 years of fusion research at Culham, near Abingdon. This is my simplified understanding …

In the early 1960s the UK Atomic Energy Authority put all its fusion research on the site at Culham. It opened in 1965 with scientists trying out different ideas to make fusion work.

Nuclear fusion is the process that powers the Sun. It works by heating and forcing together atoms so they fuse into a heavier atoms, releasing energy. To make fusion happen on Earth, the fuel must be heated to extremely high temperatures so that it becomes a state of matter called plasma. Plasma is like a gas whose atoms have been split into charged particles. Because plasma is charged, it can be held and shaped by magnetic fields which keep it away from walls long enough for fusion to happen.

In the 1970s, experiments in the USSR showed that a doughnut-shaped magnetic machine called a tokamak could hold very hot plasma better than other designs. Culham scientists built equipment to test and check these results.

In the 1980s, Culham was chosen for Europe’s biggest fusion experiment: the Joint European Torus (JET). Work started in 1978 and the first plasma was formed in 1983.

In the 1990s, Culham scientists developed a more compact form of tokamak, called the spherical tokamak. Their test device, START, ran from 1991 to 1998, and showed that this shape gave better performance for a smaller size.

In the 2000s, Culham scientists built MAST (Mega Amp Spherical Tokamak) – a bigger spherical tokamak machine. That machine, and its later upgrade were used to find out how to handle extreme heat and control plasma.

In the 2010s–2020s, JET broke records. In 2022 it produced 59 megajoules of fusion energy in 5 seconds using a fuel mix of deuterium-tritium (two types of hydrogen). They fuse to form helium and release energy.

JET ended experimentation in December 2023 and is now being decommissioned.

Meanwhile the UK is planning its first prototype fusion power station, STEP (Spherical Tokamak for Energy Production), to be built at West Burton, Nottinghamshire, a former coal-fired power station. Meanwhile, ITER, a European tokamak reactor is being built in France. Both are based on the research done and still being done at Culham.