A vacuum chamber is never perfectly empty. A small number of atoms or molecules always remains, and measuring the tiny pressures they exert is critical. For instance, semiconductor manufacturers create microchips in vacuum chambers that must be almost entirely devoid of atomic and molecular contaminants, and so they need to monitor the gas pressure in the chamber to ensure that the contaminant levels are acceptably low.

Now, scientists at the National Institute of Standards and Technology (NIST) have validated a new approach to measuring extremely low gas pressures. It’s called CAVS, for cold atom vacuum standard. They have established that their technique can serve as a “primary standard”—in other words, it can make intrinsically accurate measurements without first needing to be calibrated to reference pressure readings.

NIST researchers Dan Barker, Steve Eckel, Jim Fedchak, Julia Scherschligt, and their colleagues developed and tested a new method, known as the cold atom vacuum standard (CAVS), for measuring ultralow pressures. Credit: NIST.

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