The day the xenon exploded with X-rays, Charles Rhodes missed all the fun. In fact, he nearly called off the show. Rhodes, director of the Laboratory for Atomic, Molecular, and Radiation Physics at the University of Illinois at Chicago, was expecting a fizzle, not fireworks. It was Armon McPherson who had a hunch the xenon was poised to do something strange. McPherson, who actually runs most of the experiments, wanted to go ahead and zap the xenon with a trillion-watt laser. Rhodes thought the X-ray response would be feeble and wanted to wait until they had a more sensitive detector to pick it up. Charlie told me I’d be wasting my time, McPherson recalls. After Rhodes went home, McPherson went ahead and touched off the xenon.
Both he and Rhodes will be living with the fallout for a good many years, and they couldn’t be more delighted. The torrents of X-rays McPherson unleashed, Rhodes is now saying, may lead to the brightest source of light ever produced at any wavelength--a new kind of X-ray laser. Used in microscopes, this light would give biologists a new mode of seeing. Conventional microscopes cannot see anything smaller than the wavelength of visible light, which is a thousand times longer than that of X-rays. Electron microscopes approach X-rays in their potential to distinguish detail, but they look only at tissue stained with a metal dye and mounted, dead, on a slide. With an X-ray laser microscope, biologists could penetrate living cells. They could take holographic 3-D snapshots of structures suspended in the cell’s plasma, with details resolved to a billionth of a meter. They might even zoom down to the scale of molecules, pick out some bit of DNA, and find out how it orchestrates the chemistry of life. You wouldn’t worry about what you’d look at initially, says Rhodes. You’d just look, and you’d see something new.
Biology is only one application. X-ray lasers might also etch electronic circuits a thousand times smaller than those of today, turning a pocket calculator into a supercomputer. An X-ray beam as a communications carrier could hold a thousand bits of data in the space one bit now occupies on a conventional laser beam wending its way down an optical fiber. Because each X-ray photon packs a thousand times more energy than a photon of visible light, if you put X-ray photons in the laser beams used now for welding, cutting, and drilling, they would become powerful, penetrating weapons.
When a practical X-ray laser hits the market, says Jack Davis, a physicist at the U.S. Naval Research Laboratory, it truly is going to revolutionize everything. Davis says when, not if. The only question in his mind is who will get there first. Teams in the United States, Great Britain, France, Germany, Russia, China, and Japan have been tinkering for years with various schemes.
X-ray lasers already exist, but they are not yet practical. They come in two models. The first one was, in its heyday, the key Star Wars weapon. In 1982 Edward Teller, director emeritus of Lawrence Livermore National Laboratory in California, proposed setting off atomic bombs in space to power orbiting X-ray lasers. They would go BOOM zappa, BOOM zappa, BOOM zappa. . . . They would fry holes in approaching nuclear warheads, then themselves vaporize from the heat of their triggering bombs. Researchers actually fired up bomb-powered X-ray lasers during underground nuclear tests in the 1980s. Stephen Libby, the program’s last manager at Livermore, says only that these tests produced a robust X-ray beam, and that’s all I can tell you. Whether these lasers still exist, nobody is saying. It’s probably safe to assume that they were not reusable.
