Mode trap for absorbing transverse modes of an accelerated electron beam

In a linear accelerator comprising a waveguide that accelerates an electron beam passing therethrough, the electron beam having a transverse mode and an accelerator mode associated therewith, a mode trap to trap and absorb the transverse modes passing through the waveguide while allowing the accelerator mode to pass through the waveguide, the mode trap comprising:

• a multiplicity of electrically conductive irises and rings, each iris and ring including a respective aperture, and the irises and rings stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings define the waveguide;
• an absorbing material layer embedded in each iris and ring, the absorbing material layer encircling, but spaced from the respective aperture;
• each iris and ring further including a plurality of slots spaced around the respective aperture and extending out toward the respective absorbing material layer;
• whereby the transverse mode of the accelerator beam is channeled through the slots in the rings and irises and is absorbed by the absorbing layer, without limiting the accelerator mode of the accelerator beam.