Status of the THALES Tungsten/Osmium Mixed-Metal Hollow Cathode Neutralizer Development

Abstract

HKN 5000 hollow cathode neutralizers developed by THALES Electron Devices GmbH are based on a Tungsten/Osmium W/Os mixed metal cathode impregnated with Barium Calcium Aluminate as electron emitter. This cathode technology has a reduced work function and allows for reduced cathode temperatures and increased lifetimes compared to conventional Tungsten based cathodes. Being used as cathode material for the electron gun of Traveling Wave Tubes TWTs for satellite application, the THALES W/Os cathode technology has demonstrated more than 200 millions of successful operational hours in space. HKN 5000 neutralizers, which are being developed under support of German Space Agency DLR, are designed to deliver neutralizing currents of up to 5 A for ion thrusters, in particular for THALES High Efficiency Multi Stage Plasma Thrusters (HEMP- Ts). HKN 5000 breadboard (BB) models have shown very good performance with respect to low power and propellant consumption. Recently, HKN 5000 elegant breadboard (EBB) models have been developed, which are exclusively based on space-qualified manufacturing technologies derived from TWT production. This paper reviews the physics and technology of the THALES W/Os based hollow cathode neutralizers and presents operational and performance characteristics of the HKN 5000 BB and EBB models.