Extension of the multi-frequency ECRH system at ASDEX upgrade

A multi-megawatt Electron Cyclotron Resonance Heating (ECRH) system is in routine operation at the ASDEX Upgrade (AUG) tokamak. It applies four step-tunable gyrotrons at 105 and 140 GHz with 10 s pulse length and output powers close to 1 MW. An upgrade with four more gyrotrons is underway which will double the installed power. The first two-frequency gyrotron of the new series has recently been installed. The final goal is to have around 6.5-7 MW at 140 GHz (or 5.5 MW at 105 GHz) from 8 units available in the plasma during the whole AUG discharge (10 s).