Carbon film deposited collector electrode for high efficiency TWTs

Abstract

Collector plays a vital role in determining the overall efficiency of a TWT. Higher efficiency in helix TWTs for satellite applications is one of the stringent requirements. For the enhancement of collector efficiency, various techniques are employed like (i) multi-stage depression, (ii) use of electrode material with low secondary electron emission co-efficient, (iii) texturing of electrode inner surface etc. As the carbon exhibits low secondary electron emission properties, it is a favourable material for the collector electrodes of high efficiency TWTs. Either high density graphite or the OFHC copper coated with carbon film can be used as collector electrodes of high efficiency TWTs. In order to coat carbon on OFHC copper electrodes, a suitable RF sputtering system has been developed. Various process parameters have been optimized in order to get desired carbon film deposition on OFHC copper collector electrodes. Carbon film deposition on OFHC copper has been accomplished and characterized for the suitability to use in the multi-stage depressed collector. This paper presents the details of RF sputtering system developed, carbon film deposition process parameter optimization and characterization of carbon film deposited on OFHC copper sample.