Resumo

This paper presents the description and operational characteristics of an emissive electrode (EE) used in edge biasing experiments on small tokamak ISTTOK. The EE consists of a lanthanum hexaboride sLaB6d electron emitter heated by a tungsten filament. The emissive characteristics of EE have been investigated both in a simple vacuum diode configuration on test facility and in the plasma of tokamak. Emissive currents up to 20 A have been observed during negative bias in plasma accompanied by a strong modification of the electric field. The EE proved to be a valuable tool on the control of the plasma electric field, allowing a detailed investigation of its importance in plasma confinement.