Sun in a Bottle - Charles Seife [99]
In August 1996 and again in June 1998, researchers at Japan’s JT- 60 tokamak insisted that they had achieved “breakeven plasma conditions” and claimed their tokamak was producing 5 watts for every 4 that it consumed. A closer look showed that this wasn’t quite what happened. JT-60 was using a plasma made of deuterium, so the fusion reactions in the plasma were entirely between deuterium and deuterium. These are less energetic than deuterium-tritium reactions. If you really want to get a magnetic fusion reactor producing lots of energy, you will use a mixture of deuterium and tritium as the fuel rather than pure deuterium. JT-60’s “breakeven plasma conditions” did not really mean that the tokamak had reached breakeven. Instead, the JT-60 had reached pressures, temperatures, and confinement times that, according to calculations, would mean breakeven if researchers had used a deuterium-tritium mix rather than just deuterium as fuel. Every time JT-60 reached its “breakeven conditions,” it was still consuming much more energy than it produced. So much for Japan’s claim. What about Europe’s?
JET, the big European tokamak, actually used deuterium-tritium mixtures in attempts to achieve breakeven. In September 1997, scientists loaded up a such a mixture into the reactor, heated it, compressed it, and . . . and what? What happened? It depends on whom you ask.
Some people insist that JET reached breakeven. Britain’s Parliamentary Office on Science and Technology, for instance, states blandly in a pamphlet that “Breakeven was demonstrated at the JET experiment in the UK in 1997.” This is a myth, just like the myth about JT-60. In truth, JET got 6 watts out for every 10 it put in. It was a record, and a remarkable achievement, but a net loss of 40 percent of energy is not the hallmark of a great power plant. Scientists would claim—after twiddling with the definition of the energy put into the system—that the loss was as little as 10 percent. This might be so, but it still wasn’t breakeven; JET was losing energy, not making it.
National magnetic fusion programs are unable to achieve breakeven, let alone ignition and sustained burn. The national tokamaks like JET and JT-60 are reduced to setting lesser records: the highest temperature, the longest confinement, the highest pressure. However, these records are all but meaningless. Without getting beyond breakeven, the dream of a fusion reactor will remain out of reach. All the glowing press releases in the world won’t turn an energy-loss machine into a working fusion reactor.
Laser fusion scientists didn’t suffer nearly as much in the 1990s as their magnetic fusion counterparts. As magnetic fusion budgets sank, laser fusion ones rose, because laser fusion scientists had a secret weapon: nuclear bombs.
Publicly, laser fusion scientists billed their experiments as a way to free the world from its energy problems. What John Emmett, a Livermore laser scientist, declared to Time magazine in 1985 was typical: “Once we crack the problem of fusion, we have an assured source of energy for as long as you want to think about it. It will cease to be a reason for war or an influence on foreign affairs.” Emmett’s optimistic vision was no different from what fusion researchers had been promising since the 1950s. Just like their magnetic fusion counterparts, laser fusion scientists had promised, again and again, unlimited, clean energy. Just like their magnetic fusion counterparts, laser fusion scientists had been disappointed again and again as instabilities and other problems demolished their overly optimistic predictions. Shiva had failed, and by the 1990s, so had Nova. Inertial confinement fusion’s story was paralleling magnetic fusion’s, down to the shattered dreams and broken promises.
Less loudly, though, scientists were pushing laser fusion for a completely different reason. They weren’t really going after unlimited energy: they were pursuing laser fusion as a matter of national security. Without a working laser fusion