Validation of the cold atom vacuum standard

We report the progress towards the validation of the new cold atom vacuum standard (CAVS) via comparison to a dynamic expansion pressure standard. The CAVS is a primary pressure standard capable of sensing ultra-high vacuum (≲ 10^-6 Pa) and extreme-high vacuum (≲ 10^-9 Pa) using laser-cooled atoms (rubidium and lithium). The CAVS measures the background-gas-induced loss rate of laser-cooled atoms from a magnetic trap, which is converted to pressure using loss-rate coefficients calculated from first-principles quantum scattering theory. To validate the CAVS, we use it to measure a known pressure of a known background gas generated by a combination of flowmeter and dynamic expansion system. This system produces known partial pressures that are compatible with atom trapping (<10^-6 Pa). Here, we present our initial measurements and discuss future plans for a three-way comparison of the laboratory-scale CAVS, the dynamic expansion system, and a portable version of the CAVS meant to replace the Bayard-Alpert ionization gauge.