Magnets, not magic, make gas bulbs bad

For more than a decade, researchers have been developing a lung-imaging method in which patients inhale magnetically aligned helium-3 gas atoms. Like a magnetic dye, the noble gas makes otherwise hidden air spaces light up when viewed via magnetic resonance imaging (MRI). However, preserving the gas’s magnetic alignment has proven to be a frustrating exercise, says Brian T. Saam of the University of Utah in Salt Lake City.

That’s because the long-necked glass bulbs in which the gas becomes magnetically aligned in a laser-based process can suddenly “go bad” and destroy the magnetic order for no apparent reason, says Saam. Baffled glassware makers have been resorting to “a lot of folk art” in the vain hope of making reliable containers, Saam says. Once aligned, the helium flows into a plastic bag from which it is inhaled during the MRI scan.

The fickle bulb behavior goes beyond MRI imaging (SN: 1/3/98, p. 5). It plagues other research with noble gases, such as magnetic resonance studies of biological molecules.

A turnaround may be near. In the Oct. 1 Physical Review Letters, Saam and his coworkers report having transformed “good” bulbs to bad simply by magnetizing them using a strong magnetic field. Demagnetizing the bad bulbs made them good again.

Glass can’t ordinarily be magnetized, but the Utah experiment shows that the metal rubidium, which is needed within the container as the gas is being aligned, somehow enables the glass to become magnetic. Just how rubidium facilitates this remains unclear. Saam suspects that random exposures to magnets may be behind the mysterious behavior of the bulbs.

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