Colliding beam fusion reactor, computer artwork. This is one design for a nuclear fusion reactor that could be used for producing power. The reactor is cylindrical in shape, and powerful magnetic fields contain a high-temperature plasma (ionised gas, pink). Two beams of ions are fired into this reactor, one of protons (red, upper left) and one of boron-11 nuclei (red/blue, upper right). Neutrons are blue here. The magnetic compression of the gas allows these to fuse into helium-4 nuclei (left and right), with the production of energy. This reaction is advantageous as it does not produce neutrons, which can be damaging to the reactor and nearby humans.