Proof-of-concept pump prototype (left) and 3D simulation of the trajectories of the electrons inside the pump chamber (right).
The paper "An electrostatic ion pump with nanostructured Si field emission electron source and Ti particle collectors for supporting an ultra-high vacuum in miniaturized atom interferometry systems" was selected by the referees and the Editorial Board of the Journal of Micromechanics and Microengineering for the JMM 2016 Highlights Collection—a selection of the top 25 highest-quality papers published during the year; JMM is one of the leading journals on microelectromechanical and nanoelectromechanical systems. The article was written by Dr. Anirban Basu as first author and Dr. Luis Fernando Velásquez-García as senior author. The article reports work on a novel nanotechnology-enabled magnetic-less vacuum ion pump intended to maintain vacuum in sensors and timing devices that exploit cold-atom interferometry of alkali atoms. Cold-atom interferometry devices require ultra-high vacuum to operate; however, these devices cannot be backed up by traditional ion vacuum pumps because their performance would be degraded by interference with the pump's magnetic fields. In their novel pump design, a nanostructured silicon field emitter array generates a surplus of electrons that cause impact ionization of gas molecules, and a two-stage titanium cylindrical electron collector is used to increase the travel distance of the electrons, augmenting the ionization probability; gas ionization is subsequently followed by gettering of the ions by a negatively charged, annular-shaped titanium electrode. A proof-of-concept pump prototype was characterized using a 25 cubic cm vacuum chamber. Pumping action was observed with the electrostatic pump operating alone after an initial rapid rise of the chamber pressure due to electron/ion scrubbing, reaching a vacuum level as low as 4.47 × 10−9 Torr. A proposed reduced-order model accurately predicts the functional dependence of the pressure versus time data and provides a good estimate of the characteristic pumping time constant inferred from the experiments.
The direct links to the JMM Highlight collection and the article are:
Congratulations to Anirban and Luis!