Double-stream cyclotron wave amplifier

Experimental confirmation is reported of the theoretically predicted two-stream interactions (for circularly symmetric modes, n=0) between 1) the "fast cyclotron wave" of the slower beam and the "slow space-charge wave" of the faster beam; and between 2) the "fast space-charge wave" of the slower beam and the "slow space-charge wave" of the faster beam. The experiments were carried out at S-band. In the case of "cyclotron wave"-"space-charge wave" interaction, an electronic gain of 10 dB was measured. This double-stream interaction mode has not previously been observed. It affords the possibility of fast-wave coupling, by use of a nonuniform magnetic field along the tube, which offers size advantages at millimeter wavelengths. In the case of "space-charge wave"-"space-charge wave" interaction, the maximum electronic gain measured was 17 dB. In seeking interactions for n = ± 1 modes, none were found, due primarily to opposite polarizations, hence orthogonality, of the waves involved.