b and the rear end of the cavity 1 which determines the position of the target 11 in this position the electrons have increased their radii of rotation enabling the impact with target 11 electrons that are able to move beyond the plane where the target is located are reflected by the static magnetic field that grows in the space behind them having another chance to hit back in their movement it can also be seen in fig4 that the length of penetration of the target 11 inside the cavity 1 is defined from the average larmor radius of the electrons located in this position in an alternative embodiment of the x ray source the geometry of the resonant cavity 1 is modified the microwave mode energized in the cavity and the energization mechanism as described below in fig7 9 the basic components of an alternative embodiment of the source are shown a rectangular resonant microwave cavity 1 which is in vacuum and resonates in a te 10p mode p 1 2 3 a waveguide 2 which is coupled to the cavity 1 through an iris or resonant window 22 a microwave generator 9 connected to the coupling waveguide 6 which is coupled to the waveguide 2 through the ferrite insulators 7 three sources of magnetic field 13 u2032 13 u2033 and 13.