Techniques to raise the temperature of magnetically confined plasma to values where thermonuclear fusion can take place. The most commonly used are neutral beam injection, electron cyclotron resonance heating and ion cyclotron resonance heating. Tokamaks then use the Joule heat effect at the start of the discharge, where the weakly ionised plasma is heated by the passage of an electric current, but this method of heating does not allow fusion temperatures to be reached. Neutral beam injection injects accelerated neutral particles into the plasma, which rapidly ionize and transfer energy to the plasma by collisions. The resonance heating method transfers energy to the particles via microwaves of the same frequency as the particles circle the magnetic field lines.