Abstract: A gyrotron gun that generates gyrating electron beams in a controllable manner suitable for use in a wide range of gyro-amplifiers and gyro-oscillators is disclosed. The gyrotron comprises first and second means for abruptly changing a magnetic field and which means are positioned between first, second and third field coils. The field coils are operated so as to provide for a desired magnetic field profile that allows for the control of the parameters desired to provide for small-orbit, large-orbit, and linear modes of operation of the gyrotron gun. The gyrotron gun further comprises of a pair of bucking coils arranging near the cathode to independently control the axial velocity spread of the gyrating electron beam.