Cathode for electromagnetic wave generator with mutually mobile regions

摘要

The cathode (18) has a set of emission areas (42A, 42B) electrically connected to each other, so that the areas are at same electric potential. Each emission area is adapted to emit electrons when the areas are subjected to electric field with intensity greater than a threshold value. One of the emission areas is movable with respect to another emission area between a deployed position, in which the former emission area is away from the latter emission area, and a retracted position, in which the former emission area is adjacent to the latter emission area. An independent claim is also included for a device for generating electromagnetic waves.