First high-power tests of the 140 GHz, 10 MW CW transmission system for ECRH on the stellarator W7-X

For the fusion plasma experiment Wendelstein 7-X, which is built up at the Max-Planck-Institut fur Plasmaphysik (IPP) at Greifswald, a CW millimetre wave heating system is under construction. Initial high-power tests using a prototype gyrotron are reported and results on transmission performance as well as the behaviour of water-cooled mirrors and diagnostic components are discussed.