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

Abstract

We report a field emission-based, magnetic-less ion pump architecture for helping maintain a high vacuum within a small chamber that is compatible with miniaturized cold-atom interferometry systems. A nanostructured silicon field emitter array, with each nano-sharp tip surrounded by a self-aligned proximal gate electrode, is used to generate a surplus of electrons that cause impact ionization of gas molecules. A two-stage cylindrical electron collector, made of titanium, 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 cm 3 stainless steel vacuum chamber backed up by an external turbomolecular pump, a diaphragm pump, and a standard ion pump. Pumping action was observed with the electrostatic pump operating alone after an initial rapid rise of the chamber pressure due to electron/ion scrubbing. In addition, running the electrostatic pump in combination with the standard ion pump results in a lower vacuum level compared to the vacuum level produced by the standard ion pump acting alone. 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.

Pumping Dynamics of Cold-Atom Experiments in a Single Vacuum Chamber

“…From the observed dynamics, we can tailor the effective pumping speed and optimize the MOT loading time with respect to the contradictory requirements of having high repetition rates and high number of atoms in a single chamber. We hope that the physics investigated in this work will be useful in the future to engineer miniature and microscopic scale ion pumps [31] for cold atom based compact quantum sensors.…”

“…Finally, in Ref. [31] microfabricated non magnetic ion pumps were demonstrated with the aim of maintaining UHV conditions in miniature vacuum chambers for atom interferometry.…”

“…This dynamics is not only determined by the pumping mechanism of the SIPs but also by conductance of the whole system and the dispenser sourcing effect. Understanding this dynamics would allow, for instance, the design of miniature SIPs [31] and avoid the use of pressure gauges improving the compactness of the experiments.…”

Enhanced observation time of magneto-optical traps using micro-machined non-evaporable getter pumps

“…Designs for chip-scale cold-atom systems have also been proposed 20 and demonstrated, including novel ways of redirecting laser beams to trap atoms such as the pyramid MOT 21 , 22 and grating-MOT (GMOT) 23 – 25 , as well as density regulators 26 , 27 and low-power coils 28 . Progress has also been recently reported on the development of chip-scale ion pumps 29 . However, the high voltages and large magnetic field in the presence of the atomic sample remain unfavourable for compact atomic clocks and precision instruments.…”

Simulation-Based Model of Randomly Distributed Large-Area Field Electron Emitters

“…Field electron emitters are important for vacuum electron sources and already find applications, e.g., as cathodes in vacuum gauges [1]- [3] or X-Ray sources [4], [5]. For high current applications, large-area field emitters (LAFEs) are commonly used.…”