A leap forward for fusion power

Scientists have been trying to tweak these designs since the 1960s to find ways to put less energy into triggering fusion, or to extract more energy

The holy grail of sustainable energy is nuclear fusion. This is a potentially inexhaustible source and it has no dangerous side-effects. Fusion causes no poisonous radiation. There are no emissions of carbon compounds, or any other pollutants. 

This is the process by which stars generate energy. Atoms of some element are squeezed to fuse into a heavier element. Some leftover particles are released and converted into energy. The commonest stellar reaction squishes hydrogen (the lightest and most abundant element) till it forms helium (the second-lightest element). Stars also squeeze helium and other elements to create successively heavier elements — this