Cesium Fountain Clock — Ramsey Interrogation

The world's primary time standard works by tossing a cloud of laser-cooled cesium atoms straight up through a microwave cavity, letting them coast under gravity, and catching them falling back through that same cavity a fraction of a second later. This simulator renders that fountain in 3D: adjust the launch velocity to see the free-evolution time between the two microwave pulses stretch or shrink, sweep the microwave detuning across the resulting Ramsey fringe, and cool or heat the atom cloud to watch thermal drift carry atoms outside the cavity aperture and erode the signal the clock depends on. Live readouts track the free-evolution time, fringe width, detected fraction, and the transition's line quality factor — the same numbers that set how precisely a real fountain clock can lock onto cesium's 9,192,631,770 Hz hyperfine transition.