Abstract: A periodic permanent magnet electron beam focusing arrangement integrated with a traveling-wave tube coupled cavity slow-wave structure is disclosed which achieves maximum peak power output in a compact design of minimum size, weight and cost. A plurality of annular permanent magnets and ferromagnetic pole pieces are alternately disposed coaxially about the electron beam path, with the pole pieces extending slightly radially inwardly of the magnets. A number n (where n is a positive integer not less than two) of annular platelike members and (n - 1) annular spacer members, each of electrically conductive non-magnetic material, are disposed radially within each magnet. The inner circumferential surfaces of the spacer members and of the pole pieces constitute lateral walls for different ones of the slow-wave structure interaction cavities, the broad surfaces of the plate-like members constituting end walls for the cavities.