NIST has developed advanced cesium fountain atomic clocks, including NIST-F3 and NIST-F4, which are used to calibrate the official international time scale Coordinated Universal Time (UTC). These clocks use laser cooling to slow atoms to a fraction of a degree above absolute zero, allowing longer observation times and unprecedented accuracy. NIST-F3 provides a stable frequency reference for UTC and assists in evaluating NIST’s primary and secondary frequency standards. NIST-F4 is currently under evaluation and is expected to contribute to UTC once completed, with an accuracy approaching 10-16 fractional frequency. The next generation of atomic frequency references, such as optical clocks, aim to achieve even higher precision by utilizing laser cooling and ultra-stable lasers.
Source: https://www.nist.gov/pml/time-and-frequency-division/time-realization/cesium-fountain-atomic-clocks
Keywords: uncertainty, accuracy, lattice, resonance, frequency
