Conditioning and High Power Operation of the Lower Hybrid Current Drive Launcher in JET

The full Lower Hybrid Current Drive (LHCD) system on the Joint European Torus (JET) has been operational since the start of the pumped divertor phase of JET in 1994. By a campaign of vacuum conditioning in the beginning of operation, the power transmission and conditioning of the full launcher was speeded up, as compared with the prototype launcher used in 1990/91. After vents of the tokamak, the conditioning can be recovered by ~300 vacuum pulses over 3-4 days. Even after extensive conditioning and with efficient pumping, the power handling of the full LHCD system on plasma is limited by the maximum electric field in the waveguides, the limit being 400-500 kV/m.