Exploding wires open sharp X-ray eye

Some coffee-table books feature hair-raising microscopic views of insects, dust mites, and other minimonsters. Taken with optical and electron microscopes, those pictures typically show only surface features of their subjects. Now, a novel X-ray camera peers into the interiors of tiny creatures and objects with micrometer-scale resolution over exceptionally large areas.

In a flash, a novel X-ray camera spots micrometer-scale features (detailed below) all across this millimeter-wide fruit fly. Horizontal bars (in image above) are 25-micrometer-diameter wires included to hold the fly in place. Cornell University Laboratory of Plasma Studies

Cornell University Laboratory of Plasma Studies

Cornell University Laboratory of Plasma Studies

The new device faces stiff competition, however. Microscopists at huge electron accelerators called synchrotrons already make higher-resolution X-ray images of insects and other small objects. Nonetheless, the camera, which is the size of five refrigerators, should beat those mammoth machines hands down in comparisons of the machines’ cost and speed of imaging, says David A. Hammer of Cornell University.

“It’s a neat little imaging tool,” comments Jonathan B. Workman of Los Alamos (N.M.) National Laboratory.

Hammer and his colleagues displayed high-resolution micrographs of flies and dandelion-seed filaments at the American Physical Society’s Division of Plasma Physics meeting this week in Long Beach, Calif. The team now plans to work with Cornell agricultural researchers and veterinarians to test how well the camera differentiates tissues of germinating seeds, minute parasites in worms, and incipient tumors in mouse flesh. Hammer’s group developed the imager jointly with scientists at Russia’s Lebedev Physical Institute in Moscow.

The camera generates X rays when 100,000 amperes of electric current surge through each of two thin wires that cross. The wires vaporize. In this process, called an X-pinch, potent electrically generated magnetic fields compress tiny pockets of the resulting metal vapor to act as X-ray emitters just a micrometer or so across. The team created the camera to visualize similarly disintegrating wires for the so-called Z machine–a massive X-ray source and experimental fusion-energy device at Sandia National Laboratories in Albuquerque (SN: 1/23/99, p. 63).

Soft tissues show up in the camera’s biological images because the X-pinch device generates only low-energy beams, Hammer says. It also takes each picture with just a single X-ray pulse of about a nanosecond. The brief irradiation is so benign that the team has been able to image living specimens, such as ants, without killing them. With a synchrotron, Hammer notes, that would be a lethal experiment.

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