NISTが超低圧測定用の新しい「一次標準」を実証NIST Demonstrates a New ‘Primary Standard’ for Measuring Ultralow Pressures)


2023-08-10 米国国立標準技術研究所(NIST)

◆米国国立標準技術研究所(NIST)の科学者は、極めて低い気圧を測定する新しいアプローチ「CAVS(cold atom vacuum standard)」を開発し、これが「一次標準」として機能することを確認しました。これにより、既存の基準圧力のキャリブレーションが不要で、真の精度の高い測定が可能となりました。


Accurate measurement of the loss rate of cold atoms due to background gas collisions for the quantum-based cold atom vacuum standard

Daniel S. Barker,James A. Fedchak,Jacek Kłos,Julia Scherschligt,Abrar A. Sheikh,Eite Tiesinga,Stephen P. Eckel
AVS Quantum Science  Published:August 01 2023

NISTが超低圧測定用の新しい「一次標準」を実証NIST Demonstrates a New ‘Primary Standard’ for Measuring Ultralow Pressures)

We present the measurements of thermalized collisional rate coefficients for ultra-cold 7Li and 87Rb colliding with room-temperature He, Ne, N2, Ar, Kr, and Xe. In our experiments, a combined flowmeter and dynamic expansion system, a vacuum metrology standard, is used to set a known number density for the room-temperature background gas in the vicinity of the magnetically trapped 7Li or 87Rb clouds. Each collision with a background atom or molecule removes a 7Li or 87Rb atom from its trap, and the change in the atom loss rate with background gas density is used to determine the thermalized loss rate coefficients with fractional standard uncertainties better than 1.6% for 7Li and 2.7% for 87Rb. We find consistency—a degree of equivalence of less than one—between the measurements and recent quantum-scattering calculations of the loss rate coefficients [Kłos and Tiesinga, J. Chem. Phys. 158, 014308 (2023)], with the exception of the loss rate coefficient for both 7Li and 87Rb colliding with Ar. Nevertheless, the agreement between theory and experiment for all other studied systems provides validation that a quantum-based measurement of vacuum pressure using cold atoms also serves as a primary standard for vacuum pressure, which we refer to as the cold-atom vacuum standard.