Fusion reactors generate energy by combining atomic nuclei inside a hot electron gas called a plasma. Forcing atoms together releases huge amounts of heat which can be used to make electricity.
The plasma has to be incredibly hot. Powerful (megawatts) millimetre wave beams are used to help heat the plasma and start a reaction. Millimetre wave diagnostic systems are also used to image the plasma and help scientists understand how to keep the reaction going
Iter (featured in these photos) is the world's largest fusion reactor and the plasma temperature is 10,000,000 °C!
Reaching the temperature required for fusion while also controlling the instabilities in the resulting plasma are the main challenges that must be overcome before fusion energy can sustainably produce energy. When this becomes a reality, fusion power could solve the global energy crisis and cut carbon emissions to a small fraction of their current levels.
Visit the ITER website