1 February 2002
Storage ring may improve aircraft guidance
Atlanta—A storage ring that researchers were able to confine to guide the flow of ultracold neutral atoms in a circular path may improve aircraft guidance systems and open new areas of basic physics.
Called the "Nevatron," the storage ring-a circular wave guide that uses magnetic fields from tiny electrical wires to direct low-energy atoms-marks a step toward "atom fiber optics" that could ultimately do for ordinary uncharged atoms what optical fiber has done for light, said researchers at Georgia Institute of Technology.
"In contrast to high-energy particle storage rings in which the goal is to increase the energy of the confined particles up to and beyond the tera-electron volt scale, we are interested in the opposite regime: using ultracold atoms with nano-electron volt energies," said Michael Chapman, assistant professor of physics at Georgia Tech.
The 2-centimeter storage ring could serve as the foundation for a miniaturized atom interferometer that would improve the accuracy of inertial guidance systems used in commercial aircraft. Such systems now use optical interferometers in which a beam of light splits into two separate beams that travel in opposite directions through coils of optical fiber. By observing how changes in aircraft speed and direction differentially affect the two beams by recombining them with an interferometer, the instrument measures changes in aircraft motion.
Much heavier atoms traveling in rings feel the affect more dramatically by aircraft directional changes, Chapman said. An atom interferometer would measure phase shifts in the deBroglie wave, a quantum effect associated with atoms.
"The sensitivity of these gyroscopes is proportional to the area enclosed by the interferometer and the mass of the particle," he explained. "The mass of an atom is about 10 orders of magnitude higher than the [relativistic] mass of an optical photon."
Atomic interferometers exist but are too large for aircraft use. If Chapman's team can split an atom beam and make the beams travel in opposite directions around a circular ring, it could have the basis for an instrument small enough to fly.
"If our experiment were an interferometer, it would already have the potential to be 1,000 times more sensitive than the best optical interferometer," said Chapman. "This is really going to be a major direction in the field of ultracold atoms. Making an atomic storage ring is the first step toward useful devices."
The Nevatron also provides new opportunities for creating continuous monochromatic atomic beams that could one day lead to the development of an atom laser with a continuous output. It also offers new opportunities for studying collisions between ultracold atoms.
Other researchers have produced straight-line wave guides for neutral atoms, but the Georgia Tech ring is the first to make neutral atoms move around a closed circle using magnetic confinement.
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