Some high-power window failures

Two types of RF window failure in a high-power magnetron are investigated. Cracking is shown to depend on electrostatic charging of an evaporated metallic deposit on the window. Punctures were investigated by observation of X-ray stereo-autograms, and are shown to result from an internal multipactor discharge, which in turn is enabled to function at high voltages by the stray magnetic field. Methods for curing both types of defect are given, with evidence that they are successful. The methods are applicable to other high-power microwave tubes, both magnetrons and klystrons.