Heating experiments

Additional heating of tokamak plasma is performed by neutral beam injection and radio frequency heating. Various ranges of frequencies are used for the radio frequency heating. Mainly (i) the ion cyclotron frequency range (ICRH ≈ 10 to 150 MHz) where powerful tetrodes are used as power sources and where electron and ion heating is possible; (ii) the lower hybrid frequency range (≈1 GHz to 10 GHz) which is used mainly for current drive (LHCD) and where the power is delivered by Klystrons: (iii) the electron cyclotron frequency range (ERCH ≈ 30 to 200 GHz) where electron heating is performed and which uses gyrotrons as power sources. This last frequency band requires the simplest structures inside the tokamak achieving the highest rf power density but still requires the development of CW gyrotrons in the MW range of compare with the ICRH method. ICRH together with neutral beam injection are the most widely used methods on large machines and this lecture will concentrate on these two heating methods. If not, otherwise stated the described experimental results will be taken from the TEXTOR tokamak.