Theory of the inverted gyrotwystron

Summary form only given, as follows. The inverted gyrotwystron is a device consisting of the input waveguide, drift section, and output cavity. The traveling signal wave in the waveguide may induce a high harmonic content in the electron current density. Then the prebunched electron beam can excite phase-locked oscillations in the cavity at an arbitrary harmonic of the signal frequency. We have developed the formalism describing the operation of the inverted gyrotwystron at arbitrary harmonics. The operation of the input waveguide at the fundamental and the output cavity at the second harmonic was studied. It was shown that the electron prebunching in the input waveguide provides a better harmonic content than the ballistic prebunching in gyroklystrons. It was also shown that the dependence of the locking bandwidth on the input power is in qualitative agreement with the Adler´s relation while quantitatively the bandwidth in our device is much larger due to prebunching. The electron velocity spread causes a shrinkage of the bandwidth even when the efficiency changes only slightly.