For the transmission of microwaves at megawatt levels, waveguides must be oversized to prevent arcing due to large field intensities. Besides the advantages of oversized waveguides (low field strengths, low losses), the large number of propagable modes makes these waveguides sensitive to geometry variations.
On the other hand, systematic geometry perturbations (e.g. curvature or diameter variation) can be used to change the shape of the field inside the waveguide. This allows the design of mode converters or horn antennas with specific radiation characteristics.
Waveguide components are designed at IGVP with a dedicated computer code. Prototypes are manufactured at the IGVP workshop and low power measurements can be performed using vector network analyzers and 2D field scanners.
High power tests at 140 GHz can be performed at the ECRH facility at W7-X.