NIST scientists have developed a new portable vacuum gauge that meets Quantum SI criteria, requiring no calibration and depending on fundamental constants of nature. The gauge tracks changes in the number of cold lithium atoms trapped by a laser and magnetic fields within the vacuum, with the trapped atoms fluorescing as a result of the laser light. Every time a cold atom is struck by a molecule, the collision kicks the lithium atom out of the trap, decreasing the amount of fluorescent light emitted. A camera records the dimming, which is a sensitive measure of pressure.
The new portable system, called p-CAVS, is designed to be a “drop-in” substitute for existing vacuum gauges and is expected to replace sensors currently on the market. The NIST design uses a single laser beam directed onto an optical component known as a diffraction grating, which splits the light into multiple beams. Lithium is used because it has a low vapor pressure at room temperature and its interaction dynamics with hydrogen molecules can be calculated exactly from first principles.
The new vacuum gauge will enable researchers and manufacturers to accurately determine the vacuum level before the experiment or process begins, allowing lower levels of vacuum to be accurately measured – levels which are becoming more and more important in areas such as quantum information science.
Source: https://www.nist.gov/news-events/news/2018/10/new-way-measure-nearly-nothing
Keywords: lithium, vacuum, gauge, metrology, quantum
