Abstract: A resonant cavity arranged for an electron beam to pass therethrough, is made of two spaced apart parallel substantially planar members movable with respect to each other in a direction perpendicular to their major surfaces, at least one of said members having a delay line structure on its inner face within the gap between said two members. Means are arranged for moving the members relative to each other so as to vary the spacing between said members, whereby the oscillation frequency is tuned easily. The resonant cavity can be used to realize wide-band extended interaction oscillators and klystron amplifiers.

Abstract: A gyrotron device e.g. a gyrotron oscillator (FIG. 3) or a gyrotron amplifier (FIG. 4) in which a circular waveguide is dimensioned to operate in a transverse electric mode (TE.sub.01) as an interaction region at an RF frequency .omega..sub.o. An injection means directs a beam of electrons, in the form of a hollow cone, into the waveguide and a solenoid generates a magnetic field, extending axially along the waveguide, which causes the electrons in the beam to gyrate at the cyclotron frequency .omega..sub.c. A solenoid coil, mounted on the side of the injection means remote from the solenoid, is used to modify the magnetic field prevailing in the vicinity of the hollow cone, to cause the field lines to extend along the electron beam.

Abstract: A linear beam tube has an input section, a buffer or buncher section, and an output section.The buffer or buncher section comprises two circuits in series, each of which (FIG. 5) comprises two resonant cavities C51 and C52 through which the electron beam passes and a third resonant cavity C53 coupled to cavity C51 by a slot 53 and to cavity C52 by a slot 54.The output section (FIG. 2a) comprises two resonant cavities C1 and C2 through which the beam passes and which are coupled by a slot 5. A third resonant cavity C3 is coupled to cavity C2 by an iris 13, and to an output waveguide 14 by a further iris 15.The input section may comprise a travelling wavetube section, or the series arrangement of a standard klystron cavity and two buffer sections as shown in FIG. 5.Slot or iris couplings may be replaced by a loop coupling as known in the art.The resulting amplifier has an improved bandwidth/efficiency product.