Disk spin-down measurements in the free-molecular flow regime: A new method for measurement of tangential momentum accommodation coefficients. (April 2016)

• Record Type: Journal Article
• Authors: Acharya, Tathagata; Falgoust, Jordan; Rasmussen, Richard; Martin, Michael J.
• Is Part Of: Vacuum. Volume 126(2016)
• Page Start: 70
• Page End: 79
• Publication Date: 2016-04
• Subjects: Free molecular flow -- Tangential momentum accommodation coefficient -- Gas bearings -- Experimental fluid dynamics; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2016.01.012
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: An experimental technique using spin-down of a disk approaching the free-molecular flow limit is developed to measure the tangential momentum accommodation coefficient σt . The new technique uses a disk mounted on a shaft supported by gas bearings in vacuum. A differential scavenging system allows disk spin-down experiments in different gases. Representative test results with two different materials in two different gases are shown, demonstrating the method is capable of handling a range of gases, as well as any material that is available as, or can be formed into, a planar disk. Highlights: We show a new technology for measuring momentum accommodation coefficients. We measure momentum accommodation at the free molecular flow limit. We successfully use a gas bearing stage in vacuum. The measured momentum accommodation values range between 0.7 and 1.