Abstract: In a magnetron having a rotatable tuning member in the form of a spinner (121), a rotation sensor and an associated processor (10) generates an indication signal (11) representing the instantaneous magnetron frequency. Three level discriminators 13(1), 13(2), 13(3) are arranged to compare the indication signal (11) with respective threshold signals 14(1), 14(2), 14(3) representing different, preset frequencies. The level discriminators produce a trigger signal T effective to initiate transmission of a pulse of radiation whenever the instantaneous magnetron frequency matches one of the preset frequencies.

Abstract: In a magnetron a spinner (22), rotatable on a longitudinal axis (x) has a number of evenly spaced markings formed circumferentially on an exterior surface. The markings are sensed, as the spinner rotates, by a photo sensitive transistor (PT) coupled to window (26) in the vacuum envelope of the magnetron by a fiber optic pipe (FP1). The periodicity of pulses, generated by the transistor in response to movement of markings past the window, is divided in a network (43) to generate a succession of further pulses. The further pulses are then counted in circuit (44) and the instantaneous count compared with reference frequency values stored in memory (46) to generate an output signal O/P(1) related to the instantaneous magnetron frequency.

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.