Congress immediately seized upon it and started pouring money into fusion research. Laser fusion saw a dramatic increase in funding, growing from almost nothing to $200 million per year by decade’s end.50 Livermore and some other laboratories around the country, particularly those at Los Alamos and at the University of Rochester in New York, began to plan massive laser projects with an eye toward creating a viable fusion reactor. Magnetic fusion, too, benefited from the renewed interest in fusion energy. After stagnating for a decade at around $30 million per year, magnetic fusion budgets doubled and doubled and doubled again. In 1975, more than $100 million went to magnetic fusion; by 1977, more than $300 million; and by 1982, almost $400 million.
Siegel’s 1974 announcement helped ignite public enthusiasm (and governmental largesse) for fusion research, but his story had a tragic ending. In 1975, he keeled over while testifying about his work in front of Congress. Though he was rushed to the nearby George Washington University Hospital, he died shortly thereafter, the victim of a stroke. He was fifty-two years old. Siegel didn’t survive to benefit from the surge of optimism he generated. He also didn’t survive to see the worsening problems laser fusion scientists faced as their lasers grew more powerful.
Livermore’s Janus was already in 1975 suffering from a major snag. Its lasers were extremely powerful for their day, pouring an unprecedented amount of laser light into very tiny spaces. Livermore’s scientists managed to get this level of power by taking enormous slabs of glass made of neodymium and silicon and exciting them with a flash lamp. This glass was the heart of Livermore’s laser. The slabs were what produced an enormous number of infrared photons in lockstep. The resulting beam exited the glass and was bounced around, guided by lenses and mirrors to the target chamber. However, the beam was so intense that it would heat whatever material it touched. This heat changed the properties of lenses, mirrors, and even the air itself. When heat changes the properties of a lens or a mirror, it alters the way the device focuses the beam. These little changes in focus would start creating imperfections in the beam, such as hot and cold spots. These could be disastrous. The hot spots in the beam would pit lenses, destroying them in a tiny fraction of a second. Every time they fired the Janus laser, the machine tore itself to shreds.
Luckily, the Livermore scientists were already working toward a fix. Their next-generation fusion machine, Argus, used a clever technique to eliminate those troublesome hot spots. By shooting the beam down a long tube and carefully removing everything but the light at the very center of the beam, the scientists would be assured of getting light that was uniform and pure—and free of hot spots. This meant that the laser had to be housed in a very large building to accommodate the tubes, which were more than a hundred feet long. In addition, since they were tossing out some of the beam because of its imperfections, they were sacrificing some of the laser’s power. This was a minor inconvenience; the technique worked, and the hot spots disappeared for the time being.
More serious was the problem with electrons. Magnetic fusion researchers had trouble heating the plasma evenly; the lightweight electrons would get hot faster than the heavyweight nuclei, making for a very messy plasma soup. This problem was worse with lasers: light that is shined on a hunk of matter tends to heat the electrons first. This was a huge issue. The electrons in a laser target would get so hot that the target would explode before the nuclei got warmed up. Hot electrons and cold nuclei were no good for fusion—it was the nuclei that scientists really wanted to heat up.
For technical reasons, the bluer the laser beam, the smaller this effect. So the Livermore scientists shined the laser light through crystals that would make the infrared beam green or even ultraviolet.51 The color conversion worked well to reduce the heating of the electrons, but the process was inefficient. The beam lost some of its energy becauseof the color change. It also made the laser more expensive, as big, high-quality color-change crystals were not cheap. Nevertheless, the results—and the number of neutrons—from Argus led Livermore’s physicists to push for a full-size machine, Shiva, that would use twenty beams to zap a pellet of deuterium from all directions. It would ignite the pellet, creating a fusion reaction that would generate as much energy as the laser poured in. Or so the scientists hoped. They were wrong by a factor of ten thousand. Laser fusion scientists, like the magnetic fusion advocates that preceded them, were about to come face-to-face with a nasty instability—one so fundamental that you often encounter it in your kitchen.
It is hard to imagine an instability in the kitchen, but ask yourself the following question: When you invert a glass of water, why doesn’t the water stay in the glass? This seems like a silly thing to ask: gravity pulls the water down and onto the floor. But if you look a little more deeply, the answer is not quite so obvious. Atmospheric pressure makes the question more complicated than you might expect.
Every surface that is exposed to air is under pressure. The very weight of the atmosphere is squashing us from all directions. Every square inch of our skin is subjected to 14.7 pounds of pressure from the air pushing against us. We don’t notice it because our bodies are used to it, but this is an enormous force, easily enough to crush a steel can under the right conditions. It is also more than enough to support a glassful of water and prevent the liquid from falling to the ground. Try it yourself (over a sink, of course). Fill a glass to the rim with water. Hold a smooth, rigid piece of cardboard over the mouth of the glass and invert the whole thing. Gently let go of the cardboard. If you do it carefully enough, you will see that the water stays in the glass. The cardboard isn’t holding the water in. It’s not stuck tightly to the glass; even a gentle touch will dislodge the cardboard and cause the water to run out. And the water isn’t miraculously defying gravity. It is being supported by air pressure. The atmosphere’s upward push of 14.7 pounds per square inch is much, much stronger than the three or four ounces per square inch downward push of the water in the glass. When the two pressures go head to head, the upward push of the atmosphere wins and the water stays put. Believe it or not, the forces are so mismatched that you would need an enormously tall glass of water—about thirty feet high—if you wanted the downward-pushing weight of the water to equal the upward-pushing atmospheric pressure. With such vastly mismatched forces, the question seems a lot less stupid: Why doesn’t water stay in a glass when you turn it upside down?
RAYLEIGH-TAYLOR INSTABILITY IN A GLASS OF WATER: Invert a glass quickly and little ripples on the surface of the water will grow, becoming large blobs. The blobs break off and the water rains down out of the glass.
The water falls out because of an effect known as the Rayleigh-Taylor instability. Whenever a not-very-dense fluid (like air) pushes on a denser fluid (like water), it is an inherently unstable situation. If the interface between the two fluids has any imperfections—any bumps or divots—then those imperfections immediately get bigger and bigger.
An inverted glass of water, no matter how carefully it is inverted, has a few crests and troughs on the surface of the liquid. In a tiny fraction of a second, the crests grow, becoming enormous tendrils of water drooping down from the surface; the troughs also grow, and large fingers of air prod deep into the glass. The tendrils break, the fingers bubble off, and the entire glass of water rains down onto the floor. This is the Rayleigh-Taylor instability in action. Even though the air exerts an enormous amount of pressure on the water, the less-dense air is unable to keep the denser water contained in the glass because of these growing tendrils and fingers. Get rid of those instabilities and the air can keep the water contained. (The cardboard is not susceptible to Rayleigh-Taylor instabilities because it is a solid, so the air-pushing-on-cardboard-pushing-on-water system is stable.) But if Rayleigh-Taylor instabilities are present, then they will wreak havoc on your attempt to keep the denser fluid contained where you want it.
Laser fusion is the equivalent of keeping water trapped in an upside-down glass. As you compress a pellet of deuterium, it becomes denser and
denser. Long before you get it hot and dense enough to fuse, it will be much denser than whatever substance you are using to compress it, whether it is particles of light or a collection of hot atoms. You are using a less-dense substance to squash and contain a much denser one, and that means you will get Rayleigh-Taylor instabilities. Any tiny imperfections on the interface between the plasma and the stuff that is pushing on the plasma will immediately grow. Even an almost perfectly round sphere of deuterium will quickly become distorted, squirting tendrils in all directions. Just as this ruins any attempt to keep water in an inverted glass by means of air pressure, it seriously damages a machine’s ability to compress and contain a plasma by means of light. The only way around this was to make sure there were almost no imperfections. The target had to be perfectly smooth, and the compressing lasers had to illuminate the target completely uniformly, without any hot or cold spots that would lead to ever-growing Rayleigh-Taylor tendrils.
RAYLEIGH-TAYLOR INSTABILITY IN INERTIAL CONFINEMENT FUSION: Use lasers or particles to bombard a pellet of fuel and small imperfections on the surface of the pellet quickly become large fingers that cool the fuel and prevent it from fusing properly.
It was almost as if the laser scientists were trying to invert a glass so carefully that the surface of the water inside wouldn’t ripple at all. This is an extraordinarily difficult task. Even the twenty-armed Shiva machine, heating the plasma from twenty different directions at once, wasn’t uniform enough to keep the Rayleigh-Taylor instabilities in check. The twenty pinpricks of laser light were far enough apart from one another that they would create hot spots in the target rather than heating it uniformly. The pellet would compress, getting hot and dense enough to induce a little bit of fusion, but before the reaction really got going, the Rayleigh-Taylor instability would take over. Tendrils would form. Instead of getting denser and hotter, the deuterium would squirt out.
The Livermore scientists tried everything they could to get the Rayleigh-Taylor problem under control. One method mimicked the Teller-Ulam design for the hydrogen bomb. Instead of using the lasers to push directly onto a dollop of deuterium, the new method did it indirectly. The pellet was ensconced at the center of a hollow cylinder known as a hohlraum. Instead of striking the pellet, the lasers struck the insides of the hohlraum. The hohlraum then radiated x-rays toward the pellet. This setup is known as indirect drive, and it helped ameliorate the problems with the instabilities.
DIRECT DRIVE VERSUS INDIRECT DRIVE: In direct drive (left), laser beams shine directly on a pellet of fuel. Indirect drive (right), on the other hand, has laser light shining on a hohlraum, which evaporates and shines x-rays on the pellet.
But it didn’t do enough. Shiva, which had cost $25 million to build, only performed a fraction as well as its designers had hoped. It didn’t come close to producing as much energy from fusion as it took to run the lasers. Reaching breakeven was a much harder task than expected. The answer seemed within reach, though: just build a bigger Shiva, one with ten times the power, and ten times the price. By the beginning of the 1980s, Livermore was building a $200 million laser named Nova. Researchers there were confident Nova would finally take them to the promised land—igniting fusion fuel, producing more energy than it consumed. Once more, fusion scientists were about to have their faith severely tested.
The science of inertial confinement fusion was following the same trajectory as that of magnetic fusion. Early optimism in the 1950s led scientists to believe that plasmas could be confined and induced to fuse relatively easily. Cheap, million-dollar machines, they thought, would be able to do the job. But the plasma always seemed to wriggle out of control. Instability after instability made the magnetic bottles leak, and million-dollar machines turned into ten-million-dollar and hundred-million-dollar machines. Laser fusion began with similar optimism. Livermore’s scientists thought their first few lasers could get more energy out than they put in. But instabilities like Rayleigh-Taylor allowed the plasma to escape its confinement. Million-dollar lasers grew bigger and more expensive. Soon, laser fusion machines were as expensive as their magnetic counterparts.
Even today, decades later, these two approaches—magnetic fusion and inertial confinement fusion—remain the ways that most scientists are trying to bottle up a tiny sun. But both methods are extremely expensive, and both are plagued with instabilities that threaten to destroy the dream of unlimited fusion energy. Shiva’s failure occurred two decades after Homi J. Bhabha predicted that fusion power plants were twenty years away. Yet in the 1970s, and even into the 1980s, fusion scientists spoke of power plants as being thirty years away. After decades of research, the goal of fusion energy had become ten years more distant.
As fusion scientists built ever-bigger tokamaks and lasers for tens and hundreds of millions of dollars, outsiders began to wonder whether there was another cheaper, easier path to fusion energy. The stage was set for the biggest scientific debacle of modern times: cold fusion.
CHAPTER 6
THE COLD SHOULDER
We are also human, and we need miracles, and hope they exist.
—LEONID PONOMAREV, FUSION SCIENTIST
An intricately crafted glass mushroom on a metal pedestal, the two-foot-tall machine dominated the room—even when it wasn’t running. But when the operator twisted a dial and brought the BioCharger to life, everybody stopped to look. The helical glass coil at the top of the mushroom glowed red, and the whole machine throbbed with electricity. Tubes running up and down the mushroom’s stalk fluoresced with blue and red light. It crackled ominously as strands of violet lightning shimmied down the sides and dissipated into the air. As the crowd stood transfixed, the smiling operator turned the dial back and the machine died abruptly. The smell of ozone lingered in the air.
The BioCharger is a device that supposedly transmits healing energy directly into your body. Its inventor swears that the machine will help cure your thrush, fatigue, diarrhea, night sweats, frequent urination, colds, unrefreshed sleep, and almost anything else that ails you. The machine wouldn’t ordinarily be allowed anywhere near a scientific conference, but the BioCharger wasn’t out of place at this one. Neither was the device to test how much mercury was in your mouth to help diagnose the causes of your diseases, nor the presentation that discussed the “energy chair”: an ordinary white plastic lawn chair with a generator underneath. (“We used to call it the electric chair, but figured we had to change the name,” the presenter said.) The chair supposedly leaves you refreshed and energized after sitting in it. At an ordinary scientific gathering, such claims would be laughed out of the building. But the Second International Conference on Future Energy was no ordinary scientific conference.
Held in September 2006 on the outskirts of Washington, DC, the Conference on Future Energy was a celebration of sorts. Its convener, Thomas Valone, had recently won a long legal battle with his employer, the U.S. Patent and Trademark Office. Valone was a patent examiner who had, in his view, been fired for his belief in cold fusion. A year after being reinstated in his job (with back pay), Valone called a gathering of researchers together to, once again, explore the future of energy: a future that includes cold fusion.
Cold fusion had burst upon the world nearly two decades earlier and had long since been discredited by the mainstream scientific community. Yet today it still has a strong following, a core of true believers who think it will help humanity unleash unlimited power from fusing atoms. Plenty of reporters, government officials, and even scientists remain under its spell. The dream of unlimited energy through cold fusion is so powerful that for almost twenty years the faithful have been willing to risk ridicule and isolation to follow it.
The biggest scientific scandal of the twentieth century began on March 23, 1989. Two chemists at the University of Utah, Martin Fleischmann and Stanley Pons, told the world that they had tamed the power of fusion energy at room temperature, bottling up a miniature star in a little hunk of metal. The university’s press release was full of enthu
siasm:
SALT LAKE CITY—Two scientists have successfully created a sustained nuclear fusion reaction at room temperature in a chemistry laboratory at the University of Utah. The breakthrough means the world may someday rely on fusion for a clean, virtually inexhaustible source of energy.
At the press conference, the president of the university, Chase Peterson, pronounced that the scientists’ discovery “ranks right up there with fire, with cultivation of plants, and with electricity.” Yet such a monumental achievement came in a small and homely package. When Pons and Fleischmann displayed slides of their “reactor,” goggle-eyed reporters were stunned. The apparatus was little more than a small glass beaker mounted in a dishpan. The claim rattled around the globe in a matter of hours, astonishing physicists and igniting a tremendous controversy. Over the next few weeks, skeptics expressed graver and graver doubts about the Utah chemists’ claims, but other laboratories seemed to confirm their findings: in Utah, Georgia, Texas, Italy, Hungary, the Soviet Union, and India. The story of cold fusion quickly became a knotty mess that, decades later, has yet to be untangled.
Most physicists were immediately skeptical of the chemists’ claim, and it is easy to understand why. Pons and Fleischmann were stating that they had caused deuterium nuclei to fuse in a little jar at room temperature. This seemed to contradict everything that physicists knew about nuclear fusion. Because the positively charged deuterium nuclei must slam into each other at very high speeds to fuse, it means that fusion tends to occur only when the deuterium is at a very high temperature and high pressure. This, of course, was why fusion scientists were spending hundreds of millions of dollars on lasers and magnets to heat and confine deuterium plasmas.
Sun in a Bottle Page 13
