Electron Cyclotron Waves

An introduction is given to plasma heating and current drive with electromagnetic waves in the electron cyclotron range of frequencies, with emphasis on application in tokamak plasmas. Propagation and absorption of these waves is generally well described by linear theory, a short overview of which is given. Electron cyclotron absorption is limited to regions of the plasma where the gyromotion of electrons is in resonance with the wave frequency and can be well localised, even in smaller experiments. Apart from being able to provide global heating and non-inductive current drive, ECRH and ECCD are therefore important tools to study and manipulate locally instabilities in the plasma which are electron temperature gradient or current driven. Important potential control applications in a reactor grade plasma include mode stabilisation to prevent disruptions, transport manipulation (e.g. to maintain burn) and correction of the bootstrap current profile. The use of EC waves in major tokamak experiments has in the past been restricted due to the lack of suitable sources. These sources are, however, now rapidly becoming available.