Scientists at Sandia Labs report controlled thermonuclear fusion

Tiny hydrogen bombs might generate electricity


PHILADELPHIA - With a blast of X-rays compressing a capsule of hydrogen to conditions approaching those at the center of the sun, scientists from Sandia National Laboratories reported yesterday that they had achieved thermonuclear fusion, in essence detonating a tiny hydrogen bomb.

Such controlled explosions would not be large enough to be dangerous and might offer an alternative way of generating electricity by harnessing fusion, the process that powers the sun. Fusion combines hydrogen atoms into helium, producing bountiful energy as a byproduct.

"It's the first observation of fusion for a pulsed power source," said Dr. Ramon J. Leeper, manager of the target physics department at Sandia, in Albuquerque, N.M., who presented the findings at a meeting of the American Physical Society here.

Fusion power would be safer than fission, the current method used in nuclear power plants, because fusion does not produce long-lived radioactive waste.

Most fusion efforts have tried to use magnetic fields to compress hydrogen to temperatures hot enough for fusion to occur continuously, as it does in the sun. But sustaining a dense hot cloud of hydrogen gas has proved trickier than scientists thought when they started fusion experiments 50 years ago.

Even proponents say decades of research and expensive reactors are needed before a commercial power plant is possible. Dr. Jeff Quintenz, director of the Pulsed Power Sciences Center at Sandia, likened the approach to burning coal in a furnace.

The Sandia experiments, by comparison, could lead to something more like an internal combustion engine, in which power is generated through a series of explosions. "Squirt in a little bit of fuel, explode it," Quintenz said. "Squirt in a little bit of fuel, explode it."

That approach is potentially simpler, eliminating the need to confine hot hydrogen gas. But designing a machine that could detonate controlled thermonuclear explosions in quick succession - and survive them - is an engineering challenge that scientists have only begun to think about.

Earlier, scientists at Lawrence Livermore National Laboratory in California set off fusion explosions by shining intense lasers on hydrogen capsules. Livermore plans to further that research in a new National Ignition Facility. Other scientists are looking to implode hydrogen with beams of heavy elements like xenon or cesium.

The Sandia apparatus, the Z accelerator, was originally built to study nuclear weapons explosions without actual nuclear tests. In the mid-1990s, the Z accelerator put out an impressive 20 trillion watts of X-rays. But that was far short of what is needed to induce fusion.

Improvements have raised the peak X-ray power to more than 200 trillion watts. For billionths of a second, the power of the X-rays crashing into the hydrogen capsule far exceeds the output of all the world's power plants.

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