Novel asymmetric high efficient multi-stage depressed collector for space traveling wave tubes

High efficiency is one of the prime requirements for traveling wave tubes (TWTs) used in satellite transponders. As the collector of the TWT has a great impact on the overall efficiency, special attempts have been made to increase the collector efficiency. An ideal collector should collect all electrons at zero velocity, thereby, yielding 100% collector efficiency with zero back-streaming current. Here, authors have proposed a novel four stage depressed collector (MDC), aiming to achieve near-ideal conditions. The axis of the first electrode has been aligned with the axis of the slow-wave structure (SWS), whereas, all other electrodes have been placed off-axis with respect to the SWS. Hence, the beam as it travels along the axis of the SWS encounters axially asymmetrical electric field. A pole-piece ring has been placed around the last electrode, which enables leakage of magnetic flux in an asymmetrical manner from the periodic permanent magnet (PPM) structure. The cross-field action of electric and magnetic field, along with the asymmetry, helps achieve high collector efficiency and zero back-streaming current.