Sun in a Bottle (32 page)

It is entirely possible that after billions of dollars and decades of research, fusion scientists will take the experimental results from ITER and turn them into a design for a viable fusion reactor. No physical law stands against it, after all. But if history is any guide, a long, long road lies ahead before physicists will be able to tame fusion reactions in a bottle.

Once they succeed, will it mean anything? Though aficionados are quick to tout fusion energy as the clean, unlimited energy source of the future, it is unlikely to be terribly clean or even terribly practical. The radioactive waste it generates is somewhat easier to deal with than the corresponding waste from a fission power plant, but it is a problem nonetheless. Fusion is also expensive. ITER is likely to cost $15 billion or more to build and run, and it won’t ever be a practical reactor. Even with mass production, each fusion power plant will probably cost many billions of dollars. So long as there are other energy sources available, fusion is unlikely to make a huge dent in humanity’s energy needs.

A better candidate, despite its unpopularity, is fission. Compare it to fusion. Both have a waste problem. Fission’s is more severe, but not by much, at least in the near future. Fission plants are expensive, but they are likely to be considerably cheaper than their fusion counterparts. Fission plants are more dangerous than fusion plants (the fission reaction can get out of control, and a fusion reaction almost certainly won’t), and malefactors can process spent fuel rods to get materials for atom bombs. However, new designs (such as pebble-bed reactors) reduce the risks dramatically. Fission plants don’t have an unlimited source of fuel, but they do have enough for a century or two. And while fusion might be the energy source of the future, fission technology is already here.

Fission may not be the answer to humanity’s energy needs; we might well have to turn to fusion in the more distant future. Nevertheless, from a purely practical point of view, fission seems to be a more reasonable solution than fusion, at least in the short term. Other, non-nuclear, possibilities exist as well. For example, if we figure out how to trap and sequester carbon dioxide, we might be able to burn coal and methane without releasing greenhouse gases. Carbon sequestration schemes and advanced fission reactor designs aren’t sexy, cutting-edge science, but they are much more likely than fusion to help the next few generations of humans.

Even so, the fusion community clings to the hope that fusion energy is just thirty years away—and that it will solve
all
our energy problems. Despite the failures of the past, despite the enormous hurdles ahead, despite the tremendous cost, despite the easier alternatives, scientists still insist that fusion energy is the path forward. It is just another case of wishful thinking.

 

 

There’s something uniquely powerful about the promise of fusion energy. It harks back to the ancient quest to build a perpetual motion machine, but this time the source of unlimited energy doesn’t violate the laws of physics. To anyone who could harness the energy of a miniature star, fusion promised power. Not only would it give the world endless electrical power, it would give power to its inventors. To some scientists, this meant financial power. Still others sought the power of fame. Some saw military and political power. The rewards are so great that they can blind the scientists on the quest.

This is not to say that fusion science is worthless. Far from it. Plasma physicists have figured out the inner workings of distant stars—how they live and die. It is no coincidence that some of the world’s leading experts in stellar dynamics and supernova explosions are at Los Alamos, Livermore, and Princeton. Furthermore, fusion physicists are exploring new territory—they are looking at hotter, denser matter than anyone has yet examined—and scientists learn interesting things whenever they expand the boundaries of a field. Apparently, a pinch machine at Sandia Natural Laboratories has recently created a plasma hotter than a billion degrees. If true, it is a tremendous achievement that opens a new regime—much hotter even than the center of a star—to experimenters. That is an accomplishment in itself, but whenever physicists talk to the public about Sandia’s Z machine, fusion energy madness seems to grip them. A 2007 Sandia press release promised that “fired repeatedly, the machine could well be the fusion machine that could form the basis of an electrical generating plant only two decades away.”

It seems the wishful thinking is as strong as ever.

The promise of a fusion reactor a few decades away has been a cliché for a half century. Every time it is repeated, it just illuminates how generation after generation of scientists, drunk with the promise of personal glory and unlimited energy, keep forgetting the hard lessons learned by their predecessors. The quest to put a star in the bottle is intoxicating. Fusion might be the energy source of the future. If fusion scientists are unable to rid themselves of their intemperate self-deception, it always will be.

T
hiago Olson was an ordinary teenage boy, for the most part. He had one oddity. There was something mysterious about what he did after school. The seventeen-year-old’s friends had nicknamed Olson “the mad scientist.” For good reason: in his basement, he was building his own fusion device.

On June 20, 2006, Olson told his fellow fusion enthusiasts about his homemade “fusor,” cobbled together from parts taken from a defunct x-ray machine. “Yesterday I input power into my fusor for the first time,” he wrote, adding that he was happy to see “the familiar purple plasma” glowing away through a viewing window. Over the next weeks, Olson steadily improved his six-foot-tall device, upgrading the system that handles the deuterium gas in the machine. Three months later, Olson was making national news. “Michigan Teen Creates Nuclear Fusion,” the headlines blared.

Olson had, in fact, done it. A neutron counter implied that Olson’s fusor was producing about 200,000 neutrons a second. And though a fusion device might seem like a scary thing to keep in one’s basement, the fusor was perfectly safe. Once the headlines broke, two government radiation-safety officers and a fire marshal visited his home and gave the fusor a clean bill of safety.

On the surface, it seemed that Olson had succeeded where Pons and Fleischmann had failed. He had come up with a cheap “tabletop” device that actually achieved nuclear fusion. The public reacted with astonishment, because the cold-fusion debacle seemed to prove that tabletop fusion was impossible. However, it is not that hard to build a tabletop fusion device; people have been doing it for decades.

Indeed, Utah’s history with tabletop fusion goes back decades before the Pons and Fleischmann fiasco. The first person to achieve fusion with a cheap device was Utah born, a young man who grew up on a farm. His name was Philo Farnsworth.

Farnsworth is best known for inventing electronic television. As a young boy, he was plowing a potato field—back and forth, back and forth—when he was inspired with an idea. He could use the same back-and-forth motion to “dissect” a photographic image with a stream of electrons. Though it took years for him to perfect the device itself, at age fourteen Philo Farnsworth had invented a rudimentary television camera.

Farnsworth’s device, known as the image dissector, first turned a picture into a set of electrons. Light causes a peculiar material—cesium oxide—to emit electrons, so an image shining on a plate of cesium oxide will change from a pattern of light and dark spots into a pattern of electrons streaming from the plate. Electrons, unlike photons, are strongly affected by electric and magnetic fields, and Farnsworth exploited this property by using electromagnetic fields to move the electron image back and forth, plowlike, over a detector. This allowed Farnsworth to convert an image into an electronic format that could then be transmitted over the airwaves. Though it was a relatively crude device, it worked. The age of electronic television had begun.
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Unfortunately, a nasty patent battle ensued. Farnsworth won, but he never got rich from his invention. (Just the opposite; it nearly drove him to madness. At one point, he committed himself to an insane asylum and received shock therapy.)

Farnsworth was a brilliant inventor, particularly when it came to manipulating charged particles—like electrons—with electric and magnetic fields. So when he first heard about attempts to create a fusion reactor in a magnetic bottle, he came up with the design for a device that he thought would do it. In the 1960s, he mortgaged his house and borrowed against his life insurance to make his dream a reality. The result was the Farnsworth fusor.

While Farnsworth’s television camera manipulated electrons, his fusor manipulated deuterium nuclei. Stripped of its electrons, a deuterium nucleus has a charge equal and opposite to the electron’s; though deuterium is much more massive than an electron, it, too, can be guided and accelerated by a powerful electric field.

Over the years, Farnsworth and his colleagues patented a number of slightly different designs for the fusor, but in principle they were all relatively simple. A fusor takes deuterium nuclei (or the nuclei of other elements) and injects them into a vacuum chamber that contains a pair of charged metal electrodes. The electrodes have to be shaped to allow the nuclei to pass through them; for example, they might be two concentric wire-mesh spheres, a big positively charged sphere surrounding a smaller negatively charged one. When a deuterium nucleus is squirted past the outer sphere, it is repelled by the positive charge and attracted to the negative charge of the inner sphere, so it zooms inward with ever increasing speed. If the spheres are kept at high voltages, the ions will be moving so fast that they will overshoot the inner sphere and plunge toward the center of the device, where they might strike other ions that have fallen inward from other directions. They might even fuse, releasing energy.

The fusor wasn’t tough to build. The inventors had to be able to create a decent vacuum inside their chamber, construct electrodes designed to handle a very high voltage, and of course, get themselves some deuterium to inject into the device. Other than that, building the fusor was really pretty easy, thus well within the reach of a dedicated amateur. A small one can fit on a tabletop. And it works, too. Farnsworth got neutrons right away. Soon he and his colleagues were producing so many neutrons they had to run the device in a large pit, using the ground to shield them from the flood of particles.

Unfortunately, the Farnsworth fusor, as well as later devices that use electric fields to confine plasmas, will probably never be able to produce more energy than it gobbles up. Clever as the fusor design is, it is not a very good bottle for a star. Its electric fields let particles escape, and the motion of electrons in the plasma radiates energy away at an alarming rate. Nevertheless, fusors have acquired something of a cult following.

Young Thiago Olson’s fusor—fundamentally the same as Farnsworth’s device—is just one of more than a dozen that have sprung up in amateurs’ basements around the country. Olson was the eighteenth amateur to achieve fusion on his own, according to a roll of honor on a Farnsworth fusor aficionado Web site that Olson regularly visited. (In fact, he wasn’t the first high schooler on the list. The fifth amateur to achieve fusion, Tanhui Li, was also a high-school student; his fusor won him a scholarship in the 2003 Intel Science Talent Search.)
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Though Olson doesn’t make any claims that his device will solve the world’s energy problems, many die-hard fusor fans are convinced, hoping against hope, that fusors will soon lead to a fusion reactor—a source of unlimited energy.

On November 9, 2006, just days before the Olson story broke, the fusion physicist Robert Bussard gave a talk at Google about his research with a modified fusor. He had been working for the navy, but after a number of years he had run out of money for the program. The scientist told his audience that if he could only get his hands on $200 million, he would be able to produce a working power plant within four to five years. Bussard was deceiving himself if mainstream scientific thought is any guide. The equations of plasma physics strongly imply that fusorlike devices are very unlikely ever to produce more energy than they consume. Nature’s inexorable energy-draining powers are too hard to overcome.

Luckily, the fusor is not the only tabletop fusion device around. Plenty of researchers are building small, cheap fusion machines. Scientists without huge budgets have gotten fusion to work with inexpensive lasers, and by even stranger means.

A major hurdle with laser fusion is that electrons tend to absorb the light beam’s energy better than the heavy nuclei they are attached to. But hot electrons are pretty much useless for inducing fusion, which requires hot, fast-moving nuclei instead. In an ingenious experiment, Todd Ditmire, a Livermore physicist, figured out how to turn this liability into an asset.

Ditmire injected microscopic droplets of deuterium into a vacuum chamber and then zapped them with a cheap infrared laser. Ordinary laser fusion scientists had long since abandoned infrared lasers because infrared light heats electrons too much. However, this effect was precisely what Ditmire was looking for. When he shot the laser at the deuterium microdroplets, the laser heated up their electrons, boiling them off in a fraction of a second. The positively charged nuclei left behind, stripped of their negatively charged electrons, began repelling their neighbors. All the nuclei immediately tried to escape from one another, and the droplets exploded with great force, spewing deuterium nuclei at high speeds in all directions. Ditmire’s laser did the exact opposite of what traditional laser fusion was trying to do: instead of compressing and confining a dollop of deuterium plasma, he was causing it to blow apart. Ditmire discovered that on occasion, though, the fragments from exploding droplets—fast-moving deuterium nuclei—collide with each other and fuse. For every laser shot, he got about 1,200 neutrons from fusion. Considering that the energy of the laser was so low, less than what’s put out by a Christmas light in a second, this was an impressive fusion yield. Even so, the energy produced by the fusion was ten million times less than the energy the laser poured in. Ditmire’s scheme might be useful for studying fusion on a very tiny scale, but it will never lead to a reactor that produces more energy than it consumes.