Vacuum-pressure measurement using a magneto-optical trap

The loading dynamics of an alkali-metal-atom magneto-optical trap can be used as a reliable measure of vacuum pressure, with loading time tau indicating a pressure less than or equal to (2 x 10(-8) Torr s)/tau. This relation is accurate to approximately a factor of 2 over wide variations in trap parameters, background gas composition, or trapped alkali-metal species. The low-pressure limit of the method does depend on the trap parameters, but typically extends to below 1 x 10(-9) Torr.