Energy properties and spatial plume profile of ionic liquid ion sources based on an array of porous metal strips

Abstract

An ionic liquid ion source (ILIS) is a kind of high brightness ion source capable of providing high-speed positive or negative ion beams. This paper presents a miniaturized ILIS based on an array of porous metal strips. The porous emitter array, integrated with seven 10 mm long strips, is fabricated using wire electrical discharge machining (WEDM) combined with electrochemical etching. The assembled ILIS is 30 mm × 30 mm × 17.5 mm in size and weighs less than 25 g. A series of experiments, including an I–V characteristic test, a retarding potential analyzer (RPA) test, and a spatial plume distribution test, have been conducted in vacuo to characterize the performance of the ILIS. Results show that the emitted current is up to about 800 μA and ion transparency is as high as 94%. Besides, RPA curves reveal that the total fragmentation rate of the emitted particles accounts for 48.8% in positive mode and 59.8% in negative mode. Further, with the increase in applied acceleration voltage, the voltage loss rises while the energy efficiency decreases. It is also found that the plume perpendicular to the strips has a higher divergence than the one parallel to the strips. A numerical simulation by COMSOL reveals that the electric field distribution between the two electrodes results in such a spatial plume profile.