Multiple Beam Higher Order Mode W-Band Extended Interaction Oscillator With Improved Transmission Rate

A Compact Multi-beam Extended interaction oscillator (MBEIO) has been designed with an attempt to address the power-limitation problem associated with the fundamental-mode EIO and to improve the beam-transmission rate by making the overall-length of the cavity shorter. The W-band MBEIO operates in the $TM_{31}-2\pi$ higher-order-mode (HOM) to increase the cavity size which in turn increases the power-handling capability and relaxes the high machining-precision requirement. The overall axial-length is made shorter by exploiting the synchronous-condition and by lowering the beam-voltage which may alleviate the problem of low beam-transmission in conventional EIOs with longer beam tunnels. Both the CST-PIC and MAGIC-3D simulations predict a stable device operation after 30ns with and an output power of 7.5kW and 7.38kW respectively. Furthermore, to account for the losses due to skin effects in the W-band and surface roughness the reduced conductivity of $4.12 \times 10^{7}(S/m)$ is used for background copper material.