LINEAR-THEORY OF SLOW-WAVE CYCLOTRON INTERACTION IN DOUBLE-RIDGED FOLDED RECTANGULAR WAVE-GUIDE

A general dispersion relation for slow wave cyclotron traveling wave i nteraction in a folded waveguide is derived from a fluid dynamical tre atment. The serpentine structure is formed by folding a double-ridged rectangular waveguide so that the orientation of the magnetic field ch anges (H-plane bend) instead of the conventional E-plane bend configur ation. The H-plane bend structure has the potential for the production of high power, broad band radiation. For a cold beam, the linear theo ry predicts a gain of 2.0-2.5 dB/cm and a bandwidth of 20-25% in the m illimeter wave frequencies. The bandwidth is sensitive to the axial ve locity spread of the beam. The bandwidth decreases to 10% at delta ups ilon(z)/upsilon(z) = 3%. Means to suppress the backward wave oscillati ons have to be applied for using the full bandwidth.