Experience in integrated control of the multi-megawatt electron cyclotron heating system on the TCV tokamak: the first decade

The ECH system on the TCV tokamak consists of six gyrotrons (82.6 GHz/0.5 MW/2 s) used for X2 and electron Bernstein wave (EBW) ECH/ECCD with individual low-field-side launchers. Three additional gyrotrons (118 GHz/0.5 MW/2 s) are used for X3-ECH in a top-launch configuration to provide central heating of high-density plasmas, at nearly 3 times the cutoff density of X2. The X2 subsystem was installed by the end of 1999 and the X3 subsystem by the end of 2003, making 4.2 MW available for experiments. The installation work provides data related to testing, repair and reliability of a complex ECH system designed to allow the highest possible degree of automation, integration and flexibility in the experimental programme. Its effective integration into the TCV plant is evidenced by the fact that the mean time between shots when operating with ECH increases roughly in proportion to the increase in the resources required to prepare, monitor and record the experimental sessions. Each of the X2 and X3 subsystems is routinely individually operated by one person. This gives confidence that with proper layout, planning and integration, the EC systems of future fusion experiments, such as ITER, can routinely provide reliable actuators, on demand