X-ray Flash Fly Photography

Researchers at Cornell University have created striking images of tiny subjects, including houseflies and fruit flies, illuminated by the brilliant burst of x rays emitted by vaporizing wires. The radiographs (x-ray photographs) help to demonstrate the characteristics of the flash that erupts as 100,000 amps of current are rammed through the crossed wires of an "X-pinch" machine.

When a current courses through X-pinch wires, the metal vaporizes and leaves trails of plasma behind. In the absence of solid wires, the current continues to flow through the plasma, leading to a magnetic field that in turn pinches down on the plasma. With increasing current, the magnetic field grows and ultimately causes the plasma to implode, typically resulting in one or two dense plasma points less than a thousandth of an inch across with temperatures as high as 10 million K. The unstable plasma points emit bursts of x-rays that last less than a billionth of a second, and then the plasma points explode.

Bright, point-source x-ray bursts generated by the X-pinch machine are ideal illumination for x-ray radiographs of thin objects. Details on the order of a few millionths of a meter, such as the hairs on a fly's wing, would be impossible to discern with larger x-ray sources, but are clearly visible in images created with X-pinch flashes (see figures). Sergei Pikuz of Cornell will discuss X-pinch photography at the annual meeting of the American Physical Society's Division of Plasma Physics (Long Beach, California, Oct 29-Nov 2), while papers by T. A. Shelkovenko and D. B. Sinars will address detailed studies of the X-pinch plasma itself. (For additional information, please visit the conference's Virtual Pressroom; see a Cornell press release; or contact David Hammer, dah5@cornell.edu, 607-255-3916)