Microfabricated Noble Gas Vacuum Pump

RT&L FOCUS AREA(S): Quantum Science TECHNOLOGY AREA(S): Electronics;Materials / Processes;Sensors The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop a method for pumping noble gases at ultra-high vacuum (1e-7 to 1e-10 Torr) that is compatible with microfabricated atomic vapor cells and can either be able to be fabricated simultaneously with a silicon-based vacuum cavity or be bonded to, inserted in, or otherwise attached to a silicon-based vacuum cavity. DESCRIPTION: Atomic inertial sensors and clocks often require high or ultra-high vacuum to operate. While non-evaporable getters can provide high pumping rates for many gases, they cannot capture noble gases. As a consequence, helium and to a lesser extent argon can leak through glass windows, ultimately raising the pressure inside the vacuum cavity to unworkable levels. In laboratory scale systems, those noble gases are typically pumped out by ion pumps. While progress has been made to reduce the size of the atomic vacuum cavity [Refs 1-3], even the smallest commercial ion pumps are relatively bulky in comparison (~500 cm3 compared to < 1 cm3). Thus far, microfabricated atomic systems have either operated at higher pressures with a buffer gas, or have relied on slowing the leakage of helium from a careful selection of window material. An active noble gas pump would be a distinct advantage in creating compact, long-lifetime, ultra-high vacuum cavities. A number of commercial sensors (e.g., accelerometers, pressure sensors, microbolometers) require an evacuated chamber to meet their performance goals. Improved vacuum conditions may be able to extend the useful lifetime of these devices, but would be critical for the performance of ultra-precise inertial sensors and clocks that are particularly useful to military programs. There exist multiple avenues for innovative solutions to this problem (e.g., development of novel microstructured materials to aid in the miniaturization of ion pumps), hence the desire for an SBIR effort. Significant advances have been made to create ever-small vacuum pumps [Refs 3,4], but there does not yet exist a solution that satisfies the combination of fabrication method and pumping performance required for atomic systems. The applications for such a pump extend beyond atomic systems; any system that needs to operate at even modest vacuum (e.g., mTorr) with a glass component will ultimately be lifetime-limited by the leak rate of helium so could benefit from an improved vacuum pump. PHASE I: Perform a design and materials study to assess the feasibility of fabricating an ultra-compact vacuum pump capable of pumping noble gases at ultra-high vacuum (1e-7 to 1e-10 Torr). The study shall analyze potential approaches, exploring the risks and risk mitigation strategies associated with each, and identify the most promising option. Similarly, the study shall detail the planned fabrication process, again identifying risks and risk mitigation strategies. The study shall include an evaluation of the anticipated (goal) size (< 20 cm3), electrical power draw (< 1 W), robustness, and lifetime (> 2 yr at 10-9 Torr) of the final device. Finally, the study should discuss how the pump can be combined with a silicon-based vacuum cavity. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build prototype solutions in Phase II. PHASE II: Fabricate and test a small lot (up to Qty of 3) of the device designed in Phase I. Ensure that the prototypes are prepared in such a way that they can be bonded to a cavity and prepared for third party testing. Characterization of the components shall be performed, demonstrating their basic performance (e.g., noble gas pump speed, lowest achievable pressure) and evaluating their heat production, magnetic character, and robustness to vibration. Deliver the prototypes by the end of Phase II. PHASE III DUAL USE APPLICATIONS: Advancement of microfabricated noble gas pump technology has applications in any field that requires a long-lasting vacuum, e.g., MEMS vibration or acceleration sensors, pressure sensors, gas sensing microsystems, etc. For use in laboratory applications in chemical and biological testing. REFERENCES: 1. Kitching, John. Chip-scale atomic devices . Applied Physics Reviews 5, 031302, (2018. DOI: 10.1063/1.5026238. https://aip.scitation.org/doi/10.1063/1.5026238. 2. Knapkiewicz, Pawel. Technological Assessment of MEMS Alkali Vapor Cells for Atomic References. Micromachines 2019, 10(1), 25. DOI: 10.3390/mi10010025. https://www.mdpi.com/2072-666X/10/1/25/htm. 3. Knapkiewicz, Pawel. Alkali Vapor MEMS Cells Technology toward High-Vacuum Self-Pumping MEMS Cell for Atomic Spectroscopy. Micromachines 2018, 9(8), 405. DOI: 10.3390/mi9080405. https://www.mdpi.com/2072-666X/9/8/405. 4. Grzebyk, Tomasz. "MEMS Vacuum Pumps." Journal of Microelectromechanical Systems, Vol. 26, Issue4, August 2017. DOI: 10.1109/JMEMS.2017.2676820. https://ieeexplore.ieee.org/document/7888534.