



01586nas a2200193   4500008004100000245007900041210006900120260001400189490000700203520099200210100002401202700002201226700002201248700001901270700002001289700002701309700001901336856003701355       2017                        eng d00aDevelopment of a new UHV/XHV pressure standard (cold atom vacuum standard)0 aDevelopment of a new UHVXHV pressure standard cold atom vacuum s  c2017/11/30 v543 a<p>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.</p>1 aScherschligt, Julia1 aFedchak, James, A1 aBarker, Daniel, S1 aEckel, Stephen1 aKlimov, Nikolai1 aMakrides, Constantinos1 aTiesinga, Eite  uhttps://arxiv.org/abs/1801.10120