Electrospray emitters For diffusion vacuum pumps

Abstract

Following similar principles as regular diffusion vacuum pumps, an electrospray emitter is set to produce a jet of charged particles that will drag air molecules out of a volume. To be a feasible concept, the emitted particles should have enough momentum to make the colliding air particles being effectively removed from the volume. Also the density of the droplets should be such that the mean free path of air molecules to electrosprayed droplets is in the order of magnitude of the testing setup. A theoretical model is developed for estimating the pumping speed and the importance of the conductivity of the working fluid is identified. Experimental results show an interesting effect. as the pressure difference between two volumes separated by an aperture, is reduced when an electrospray emitter is on. It is showed that a single emitter is expected to have a very low pump capacity, so an array of emitters is proposed as solution. This thesis also comments on the applicability of powder compression molding for the fabrication of emitter arrays. Powder compression molding consists in manufacturing the emitter array out of a plastic - metallic powder feedstock. It consists on 4 steps: (1) Mixing of feedstock, (2) Compression molding, (3) Debinding and (4) Sintering. Initial experiments on compression molding are successful in reproducing arrays of micropillars.