Measuring pressure with a cold-atom vacuum standard
First, researchers attach the cold-atom vacuum standard (CAVS) device to the vacuum chamber they want to measure. When the CAVS and vacuum chamber reach equilibrium pressure, lithium atoms are introduced into the CAVS. As the atoms move into the device chamber, they are slowed by laser light and then captured by a combination of laser light and magnetic fields. This trapping process causes the atoms to fluoresce, emitting light in all directions. Some of the emitted light is captured by a detector. When a molecule of background gas collides with a trapped atom, it can knock the atom out of the trap. Every time an atom is lost from the trap, the total fluorescence diminishes. By measuring changes to the emitted light, researchers can measure the rate at which atoms are lost from the trap, which provides a sensitive indicator of pressure in the chamber.
October 2018 • NIST • https://www.nist.gov/news-events/news/2018/10/new-way-measure-nearly-nothing • Tagged: Animation