Additional heating power supplies: Design concept and first operation

Two additional heating methods are used in JET, e.g. the Neutral Injection (NI heating) and the Ion Cyclotron Resonance Heating (RF Heating). In the RF heating, 10 generators each deliver 3MW to their antenna; for the NI heating 16 ion sources each delivering 4.8MW ion beam are installed. In order to minimize the internal dissipation in the generator and hence to obtain the maximum output power of the RF generators under the varying load conditions given by the plasma, the high voltage on the anode of the tetrode is varied. This is one of the main features of the power supply. The requirements for the NI power supply are different to the ones for the RF power supply. The accelerating grid (G1) power supply has to be very stable and must be able to switch off in 10 microsec in case of a breakdown in the accelerating structure and re-apply within 50 ms. Both these functions, voltage regulation and switching on and off are performed by a high power tetrode (protection system). In addition to the accelerating grid power supply, other power supplies (Aux PS) are necessary. They are the arc power supply, the filament power supply, the suppression grid (G3) power supply, the gradient grid (G2) power supply and the bending magnet power supply