Electron heating in a magnetically confined plasma by microwaves. If the frequency of the electromagnetic wave is equal to the frequency at which an electron gyrates about a magnetic field line, i.e. electron cyclotron frequency, this electron absorbs energy from the wave. High frequency waves, tens to hundreds of gigahertz, are used, selecting a frequency corresponding to multiples of the cyclotron frequency of the electrons in the device. The heated electrons then transfer their energy to the ions by collisions, thus heating the plasma. It is also possible to heat only a specific part of the plasma. The microwave radiation for heating the electrons is supplied by gyrotrons.