NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the .br NIST has officially launched NIST-F2 More Info: NIST-F2, a new atomic clock based on a fountain of cesium atoms, is now the U.S. .br ʬ NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as .