Development of a new UHV/XHV pressure standard (cold atom vacuum standard)

TL;DR

This paper introduces a novel vacuum pressure standard based on ultra-cold atoms, capable of measuring ultra-high to extreme-high vacuum pressures with primary traceability from atomic collision data.

Contribution

It develops a primary, absolute vacuum standard using cold atom loss rates, extending pressure measurement capabilities into ultra-high vacuum ranges.

Findings

Demonstrates a new method for pressure measurement using cold atom loss.

Provides a primary standard based on ab initio collision cross sections.

Extends pressure measurement into 1 x 10^-6 to 1 x^-10 Pa range.

Abstract

The National Institute of Standards and Technology has recently begun a program to develop a primary pressure standard that is based on ultra-cold atoms, covering a pressure range of 1 x 10-6 to 1 x 10-10 Pa and possibly lower. These pressures correspond to the entire ultra-high vacuum range and extend into the extreme-high vacuum. This cold-atom vacuum standard (CAVS) is both a primary standard and absolute sensor of vacuum. The CAVS is based on the loss of cold, sensor atoms (such as the alkali-metal lithium) from a magnetic trap due to collisions with the background gas (primarily H2) in the vacuum. The pressure is determined from a thermally-averaged collision cross section, which is a fundamental atomic property, and the measured loss rate. The CAVS is primary because it will use collision cross sections determined from ab initio calculations for the Li + H2 system. Primary traceability is transferred to other systems of interest using sensitivity coefficients.