High Power Tests of Beryllium Oxide Windows to the Lower Hybrid Current Drive Launcher in JET

The vacuum windows to the 3.70 GHz Lower Hybrid Current Drive (LHCD) system in JET were originally designed to withstand 350 kW for 20s with VSWR ≤ 1.8. High power RF tests of the windows have been carried out in the LHCD test facility at JET. All windows that were tested could operate at 500 kW for 10s in a matched load. Two windows passed an endurance test at 250 kW for 20s with the windows terminated in a short circuit. One window also passed this endurance test without active cooling. The results show that this type of window can be used in a new advanced launcher, as proposed for ITER, in which the output power from each klystron (P ≤ 500 kW) will be transmitted through one waveguide and one vacuum window.