Sun in a Bottle - Charles Seife [56]
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