Sun in a Bottle - Charles Seife [66]
The fusion of two deuterium nuclei produces a fixed amount of energy: the energy that the particles get from rolling one step down the fusion hill toward the valley of iron. That energy is carried away by the particles created by the reaction. For the branch of the reaction that creates a neutron and a helium-3, the total energy released—in the units that nuclear physicists like to use—is nearly 3.3 million electron volts (3.3 MeV).55 That energy is split between the two particles. Furthermore, the heavier particle gets less energy, while the lighter particle gets more.56 In this particular case, the heavier helium-3 gets about 0.82 MeV while the lighter neutron gets 2.45 MeV. Every time. So, if you find neutrons flying about with 2.45 MeV of energy, it is a really good sign that you are seeing deuterium-deuterium fusion.
Before the press conference, Pons, Fleischmann, and Jones had all been looking for neutrons. Jones’s team thought it had found a few coming from their experiments—a small, unimpressive bump in a graph. The bump didn’t represent a solid discovery; after months of running the experiment, Jones claimed to see roughly twenty neutrons in the 2.45 MeV range. Unimpressive, yes, but Jones considered them a solid sign of fusion reactions. That these neutrons were there at all “provides strong evidence that room-temperature nuclear fusion is occurring at a low rate” in the experiment, Jones later wrote. Pons and Fleischmann had been looking, too, but they were having even less luck. Fleischmann used his Harwell laboratory connections to get a neutron detector, but when they put it near the cell, it didn’t show any neutrons. This was a huge problem, because for every watt of power the cell produced, about a trillion neutrons should have been flying out every second. At the power levels Pons and Fleischmann were seeing, their beaker should have been emitting dangerous and easily detectable levels of radioactivity. But it wasn’t.
As the days of fruitless searching turned into weeks and the time of the press conference drew closer, Pons and Fleischmann evidently became increasingly concerned. They sent a cell to Harwell to be analyzed with a much more sensitive machine, but the analysis required some time. In the interim, they invited a person from the University of Utah’s radiation safety office to the lab to measure gamma rays coming from the cell. The gamma rays, they hoped, would provide an indirect measure of neutrons: when a 2.45 MeV neutron strikes a hydrogen in the water surrounding the palladium, it will emit a gamma ray, again with a very specific energy: 2.22 MeV. The safety officer set up a gamma-ray detector for a few days and collected data. Apparently, Pons and Fleischmann were thrilled with what the machine found, because shortly after analyzing the data, they submitted their paper to the Journal of Electroanalytical Chemistry and Utah began setting up the press conference.
When Pons and Fleischmann announced their discovery to the world on March 23, 1989, Utahans immediately sought to capitalize on the news. The day after the press conference, Governor Norman Bangerter announced that he would call a special session of the legislature to appropriate $5 million for cold-fusion research. The appropriations bill passed overwhelmingly. The money would help establish a National Institute for Cold Fusion at Utah. Soon cold-fusion lobbyists would be marching up Capitol Hill seeking tens of millions of dollars, promising that Japan would steal cold-fusion momentum away from the United States if the nation didn’t invest immediately.
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