Probe bares heart of X-ray inferno

Despite torrents of high-energy radiation, physicists have captured images of explosions that lead to some of the world’s most powerful bursts of X rays. The snapshots reveal previously unseen details of fiery disintegrations at the core of a giant, energy-focusing machine called Z. Scientists at Sandia National Laboratories in Albuquerque, N.M., use the device to simulate nuclear-weapons detonations and to research nuclear fusion as a potential power source (SN: 4/19/03, p. 252: Available to subscribers at Fusion device crosses threshold).

VAPOR CAPER. Spotty breakdowns of metal wires (top) spawn streaks in vapor (bottom) that limit X-ray power. C. Coverdale, B. Jones, Sinars/Sandia

To trigger one of Z’s enormous X-ray blasts, scientists send a submicrosecond pulse of millions of amperes of electric current racing through a palm-size cage of metal threads at the center of the sprawling apparatus. The wires explode into vapor that then gets compressed and emits the X rays.

Sandia’s Daniel B. Sinars and his colleagues have now plucked from Z’s X-ray deluge a grainy record of those wires’ fates. The trick, Sinars explains, was to pipe in additional X rays from outside the machine that would be used exclusively for picture taking and that wouldn’t overwhelm or destroy the X-ray detector.

Sinars says that the images confirm suspicions that even this mightiest of so-called pulsed-power devices suffers from uneven vaporization of its wires. Now that Z specialists can see what’s going on, they may devise ways to improve the uniformity of the wire explosions and, consequently, Z performance.

Sinars presented the images and the new method for obtaining them last November at a plasma-physics meeting in Savannah, Ga.

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