ITER ECRH protection: Microwave stray radiation exposure of in-vessel components*

At ITER, for first operation 24 gyrotrons at 170 GHz with 1 MW power each are being prepared for ECRH and ECCD. Using the O1 heating scheme, absorption of the injected power is full. But practical limitations in relaying and launching the power will lead to a fraction of non-absorbed power. This power is incident on in-vessel component, risking excessive heating. At Wendelstein 7-X (W7-X), with ten gyrotrons at 140 GHz with up to 1 MW each, this problem was also anticipated and a microwave stray radiation test facility was built to test in-vessel components at isotropic power densities of up to 50 kW/m2 for up to 30 minutes. The facility is also operated in support of the ITER ECRH protection, for instance, exposing the Mirnov coil covers and future ITER proto type vacuum windows. The temperature increase, as well as the rate of temperature increase, of ceramics are measured as function of power density and exposure time. Various shielding concepts using metal foils, meshes and reflecting coatings are being assessed. Results are discussed in this contribution.