NIST is developing a cold-atom vacuum sensor (CAVS) to measure ultra-high vacuum (UHV) pressures down to 10-9 torr, where no reliable tools currently exist. The sensor works by measuring the loss of ultracold lithium atoms from a magnetic trap due to collisions with room-temperature background atoms and molecules. The dominant background constituent is molecular hydrogen, though other gases can be introduced intentionally.
The sensor’s operation is based on the relationship between the time constant for lithium atom loss and the number density of background atoms and molecules. This allows the pressure to be calculated using the ideal gas law. The research team has already determined elastic rate coefficients and cross sections for molecular hydrogen and helium atoms with the desired accuracy, and calculations for other species are underway.
The potential impact of this work is significant, as it could provide a new standard for measuring UHV pressures, which are crucial for many scientific and industrial applications. The implementation timeframe for the CAVS is not specified in the article, but the research is ongoing and collaboration with the Thermodynamic Metrology group of the Sensor Science Division is mentioned.
Keywords: Vacuum, Pressure, Lithium, Atomic, Collision
