January 2001

Bad Vibrations

NIST hopes to stifle the tremors that ruin experiments.

By Ivan Amato

The National Institute of Standards and Technology is famous for always taking the art and science of measurement to the next decimal place. Now, tons of dirt are moving at NIST's headquarters in Gaithersburg, Md., to make way for a world-class laboratory hosting some of the most tightly controlled environments on the planet.

The argument for the Advanced Measurement Laboratory (AML) is simple: NIST's buildings, which were constructed nearly 40 years ago when integrated circuits were new, can't handle ever more demanding measurement research. "We have to start over," says physicist Robert Celotta, a NIST veteran looking toward an era of nanoscience and nanoengineering. Already, some of NIST's instruments are so sensitive that spark plugs firing almost a kilometer away disturb them.

How annoying can that be to researchers who measure quadrillionth-of-a-second laser pulses and interatomic distances on semiconductor crystals? NIST Director Raymond Kammer waves his hands as though he were steadying himself on a shaky subway. "From the perspective of an atom, this is what it's like here," he says. Besides vibration, airborne particles and fluctuating temperature and humidity also are showstoppers.

This past September, NIST announced it had signed a $174 million construction contract; work was slated to begin before the end of 2000. If the AML lives up to its design specs when its doors open in 2004, its steadiest laboratory surfaces will move less than a picometer (a trillionth of a meter) per second. That's "a fraction of an atomic width," says Celotta. In many of the AML's underground laboratories, floors suspended on arrays of computer-controlled and pneumatically adjustable air springs will quell low-frequency vibrations. Atop these, vibration-isolation tables with their own suspensions will dampen higher-frequency tremors. And some instruments will rely on additional thermal, magnetic and electromagnetic shields to combat even the subtlest forces.

To eradicate particles, the air in the AML's cleanest spaces will change over 300 times per hour, flowing through ceilings made almost entirely of filters. Most of the AML is expected to average about 30 particles per liter of air, down from the 70,000 to 100,000 particle counts in NIST's general-purpose labs. To reduce temperature fluctuations to as low as one-hundredth of a degree Celsius and humidity variations down to 1 percent, arrays of precise thermometers and humidity sensors in each laboratory will feed data into computers that control the AML's heaters and coolers.

Celotta, for one, looks forward to installing his new microscope at the AML, and examining surfaces atom by atom, in perfect stillness.