NIST's clocks -- the timepiece that sets the rest

Wired's published part two of Quinn Norton's excellent investigative feature on time-hackers, hobbyists who build hyper-accurate timepieces using surplus atomic components. Today, Quinn visits NIST and sees how the time-pros do it, investigating the latest generation of fiendishly precise timepieces that are used to set the time for all the other clocks in the land.

A visitor to the lab housing the NIST-F1 might be forgiven for casting an appreciative glance at a sleek refrigerator in the corner of the room, instead of the jumble of mirrors and lenses powering the F1. But like all modern atomic clocks, the NIST-F1 relies on laser light to coax precise time from elements -- in this case cesium 133. Once the focused light leaves its piping, it's split into six lasers, all directed into the cylindrical cesium fountain that rises to nearly meet the ceiling.

Inside the vacuum of the fountain, the lasers focus on a gas containing around a million cesium atoms, gently slowing them to near motionlessness and gathering them into a very loose ball. Two of the lasers are oriented vertically, and they toss the ball up through the tube, then let gravity take it down again -- a process that takes about a second.

During that second, a microwave signal bombards the cesium ball. When the ball reaches the bottom of the cylinder, a laser and detector examine the state of the atoms. The closer the microwave signal comes to the cesium's resonance frequency, the more the atoms will increase in fluorescence. That allows the machine to continuously adjust its microwave signal to approximate, though never reach, the precise 9,192,631,770 cycles per second of the cesium-133 atoms.

Link

See also: Time hackers build cesium clocks, live longer than the rest of us

[#1 posted by ianm , December 12, 2007 6:15 PM]

Great article, thanks for the link. I also read the one last week on the supercomputer conference. These new (if not new, at least new to me) Wired photo-writeup-feature-things are very compelling, high-fiber info snacking indeed!