This sort of evidence would not convince most physicists. To them, the only way to prove that you have achieved fusion is, naturally enough, to show that you are producing some of the by-products of fusion. With deuterium-deuterium fusion, there are a few unambiguous signals that a reaction has taken place.
When two deuterium nuclei fuse (d + d), they stick together for a tiny fraction of a second: two protons and two neutrons in a quivering, energetic bundle. Because the conglomerate is so energetic, it cannot hold together completely. One particle is going to pop off and carry away some excess energy. That means either a proton (p) is going to pop off, leaving behind a tritium particle (t) with one proton and two neutrons,
d + d → p + t,
or a neutron (n) is going to pop off, leaving behind a helium-3 nucleus with two protons and one neutron,
d + d → n + 3He.
These two branches of the reaction are roughly equally likely: half of the time that you fuse two deuterium nuclei, you will get a proton and a tritium nucleus; the other half, a neutron and a helium-3 nucleus.
Free-floating protons are relatively common, but free-floating neutrons are rarer, as are tritium and helium-3. So if you think that you’ve got deuterium-deuterium fusion going on in your laboratory, the best way to convince other people is to demonstrate that you are making tritium, helium-3, and neutrons. The neutrons, arguably, should be the easiest to detect. Neutrons penetrate matter very easily, so any neutrons produced by the reaction would quickly fly out through the walls of the beaker and into the walls surrounding the room. A neutron detector need only be placed next to the reactor vessel and it would certainly pick up some of these particles. There are neutrons from other sources—cosmic rays, for example, often produce them in the lab—but luckily the neutrons from deuterium-deuterium fusion have a specific energy.
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.
The scientific community was of two minds. Some were optimistic. Edward Teller called to congratulate Pons and Fleischmann and started a Livermore task force to look into cold fusion. Others, including the University of Utah’s own physics department, which had been kept in the dark by the chemists, were extremely wary of the results. No matter the level of skepticism, every scientist wanted details about the experiments, and there were few to be had.
Pons and Fleischmann had held their press conference before publishing their data and their methods. This was very unusual. Scientists communicate through scientific presentations and papers, not through press releases and press conferences. On the relatively rare occasions that a scientific result is important enough to merit a press event, it is usually held at the same moment that the data are revealed to the scientific community through a paper or in a presentation. With the cold-fusion announcement, the paper was missing. No data were available, and scientists had only the scantest details about how Pons and Fleischmann performed their experiment.
Physicists and chemists around the world were frantic; without any data, they had little way to judge whether Pons and Fleischmann were going to solve the world’s energy crisis—or whether they were merely full of it. The suspense would last for months.
In the first few days after the press conference, the news seemed good for the two chemists. The press soon learned about Jones’s work, and while Jones was much less bold in claiming to generate energy, he, too, was claiming to see fusion in palladium. It appeared to be an outside confirmation of the Pons and Fleischmann claim. No longer could cold fusion be considered the delusion of a single laboratory. As other labs rushed to replicate the experiments, news began to filter in about other confirmations. By early April, researchers at Texas A&M were seeing excess heat in palladium cells; Georgia Tech was seeing neutrons. The University of Washington was seeing tritium. These reports all seemed to provide solid support for cold fusion.
Privately, though, Pons and Fleischmann were getting bad news. Two days before the press conference, Fleischmann learned that even the hypersensitive neutron detector at Harwell wasn’t picking up anything. There was no trace of the trillions and trillions of neutrons that should have been flowing from the palladium. Fleischmann apparently explained the discrepancy away, noting that a number of cells that he and Pons had built didn’t work; perhaps Harwell was using a defunct cell. It was not a convincing explanation, but it would have to do. But worse news was to come, news that was harder to dismiss.
Four days after the press conference, Pons and Fleischmann began to reveal details of the experiments to some of their colleagues. Fleischmann visited the Harwell lab and gave a seminar on cold fusion. The room was packed with scientists, including some very esteemed ones who had been working with neutrons and gamma rays for years. When Fleischmann showed his gamma-ray measu
rements to the Harwell crowd, they were shocked. A typical gamma-ray spectrum is a bumpy graph that shows a series of peaks and troughs at various energies, reflecting natural background sources of gamma radiation (such as the decay of radioactive elements). Gamma rays from deuterium should have occurred at 2.22 MeV, right between a gentle peak caused by the decay of radioactive bismuth at 2.20 MeV and a much larger one caused by the decay of radioactive thallium at 2.61 MeV. Instead, Fleischmann showed a ratty little plot that displayed only a single peak, without any nearby landmarks to confirm what the peak really was. Worse yet, Fleischmann was claiming that he was seeing gamma rays that had 2.5 MeV of energy, not the 2.22 MeV that a fusion neutron should emit when it strikes a tub of water.57 The peak was in entirely the wrong place. The director of Harwell turned to Fleischmann and said, simply, “It’s wrong.” Fleischmann wilted. The next day, physicists at the University of Utah—who had been given a preprint of the upcoming cold-fusion paper—told Pons precisely the same thing.
What was going on? Why was the gamma-ray peak in the wrong place? To all appearances, Fleischmann and Pons dismissed the problem, attributing it to a minor error in calculation. When their paper finally came out in the Journal of Electroanalytical Chemistry, the lone peak was sitting in precisely the right spot: 2.22 MeV. Perhaps they told the editors about the “error” and corrected it before it was published. However, Pons and Fleischmann apparently failed to spot one occurrence of the old, incorrect value of 2.5 MeV in the manuscript: in the equation where they describe the interaction between a neutron and a hydrogen atom, they declare that the gamma ray would be at 2.5 MeV, not the 2.22 MeV shown by the spectrum.
The problem of the moving peak wasn’t public yet, though it soon would be. In the days after the press conference, scientists, still hungry for details about the Pons and Fleischmann experiments, were taking desperate measures. Physicists apparently hacked into Pons’s e-mail account looking for clues. One scientist spooked Utah chemists by loitering outside the Pons-Fleischmann lab. A team of plasma physicists at the Massachusetts Institute of Technology resorted to scouring television footage of the lab instruments for data. They succeeded: a broadcast on Utah’s KSL-TV showed the entire gamma-ray spectrum, clearly showing the bismuth and thallium peaks. Using that information, they deduced that Pons and Fleischmann’s peak had to be near 2.5 MeV as originally presented during the seminar at Harwell, not at 2.22 MeV, as reported in the journal article. Furthermore, even without the television footage, the MIT researchers showed that the Pons-Fleischmann peak was the wrong shape—too narrow and without a distinctive shoulder—for one produced by neutron-created gamma rays. It was a devastating critique, and when Pons and Fleischmann responded to the MIT criticisms in June, the peak had somehow moved back to 2.5 MeV. By that time, most mainstream physicists had already decided that cold fusion was bunk.
However, in late March and early April, the question was still open. While the physicists were still trying to figure out precisely what Pons and Fleischmann had done, the scientific and political communities were dividing into believers and nonbelievers. The biggest critics of cold fusion were plasma physicists. These were the people who knew a lot about the difficulty of achieving fusion, and who had learned through painful experience how neutrons can fool you. They were also the people who had the most to lose if cold fusion worked. Cold-fusion supporters began to sense a conspiracy to attack the Pons-Fleischmann discovery. “There is big money in hot fusion, and if we turn out to be right, hot fusion, I guess, goes away,” said the University of Utah president, Chase Peterson. “That represents entire careers, and orthodontia, and college educations for whole families of people that have lived off that dole.” In the eyes of supporters, the critics of cold fusion, largely on the East and West Coasts, threatened with obsolescence, were striking at the discoverers of cold fusion in Utah, in the heartland. The university’s vice president for research, James Brophy, supported this view: “The black hats, such as they were, came from the hot fusion community.... There was certainly an organized campaign to discredit cold fusion based on the possibility of losing funding.”
On the other side, anti-cold-fusion physicists felt that they were simply trying to investigate a very important scientific claim; after all, the whole scientific method relies on the vigilance of the scientific community. Even skeptical fusion scientists, such as Richard Garwin, who helped turn the Teller-Ulam design into a testable bomb, investigated the Pons and Fleischmann claims with an open mind. “Within the next few weeks, experiments will surely show whether cold fusion is taking place; if so it will teach us much besides humility,” he wrote in April 1989, even though he himself “bet against its confirmation.” But the lack of details from Pons and Fleischmann was frustrating physicists who were trying to confirm the cold-fusion experiments using data gleaned from television broadcasts and newspaper photographs.
Throughout April, the pro-cold-fusion groups had the momentum. Though MIT researchers had reported that they were unable to replicate the experiments in mid-April, there were the confirmatory results on the other side: Jones, Georgia Tech’s neutrons, and Texas A&M’s heat. When Pons spoke at a hastily cobbled-together special session at the American Chemical Society meeting on April 12, the mood was enthusiastic. The crowd was extremely sympathetic, if for no other reason than the hope that fellowchemists would succeed where physicists had failed. Physicists had spent years trying to harness the power of fusion, noted the American Chemical Society’s president in his introduction to Pons’s presentation. “Now it appears that chemists may have come to the rescue,” he said, triggering applause and laughter. But Pons’s presentation generated serious doubts in the audience. Most troubling was when he fielded questions about his control experiments.
If Pons and Fleischmann were actually seeing fusion in a test tube, they should have been able to show that the effect was not due to a quirk in their apparatus. To do this, they needed to run a control experiment—one that was almost identical to the fusion cell, but subtly different in a way that would prevent fusion from occurring. Only then could they prove that fusion was really responsible for the excess heat and other effects they were seeing. In the Pons and Fleischmann case, the obvious control experiment was to run an identical experiment with ordinary water rather than heavy, deuterium-laden water. If deuterium-deuterium fusion was responsible for the excess heat, getting rid of the deuterium and replacing it with ordinary hydrogen should end the fusion and turn the heating off. They then could be assured that the heat had something to do with the deuterium in the beaker. Doing this was absolutely necessary if Pons and Fleischmann were to prove to other scientists that they were not deluding themselves.
Indeed, this sort of control experiment is what budding scientists are taught to do in freshman science classes, and everybody expected it from such established scientists as Pons and Fleischmann—not to have run one would seem absurd. But when questioned about why Pons had not published any control experiments, his reply was cryptic. “We do not get the total blank experiment that we expected,” he said. Was he really implying that fusion occurred in the absence of deuterium? This seemed ridiculous even if you accepted that a miracle occurred inside the palladium cell.
At the very least, the scientific community wanted to see the results of those control experiments, but neither the Journal of Electroanalytical Chemistry paper nor the one that Pons and Fleischmann submitted to Nature had any sign of such a control. “How is this astounding oversight to be explained to students. . . . And how should the neglect be explained to the world at large?” asked John Maddox, the editor of Nature. This was poor science at best, although it was beginning to look much worse than that.
After Nature received the twin manuscripts from Pons and Fleischmann and Jones, the journal sent them out for peer review. The reviewers made their suggestions for changes and additional work, and these were sent back to the authors. Jones complied with the reviewers’ requests, but Pons and Fleischmann refused to
do so, claiming they were too busy with other “urgent work.” Though Nature emphasized that this did not make the Pons-Fleischmann paper any less believable than Jones’s, it was still a deep blow to the team’s credibility. Many physicists were beginning to smell a rat, and the rhetoric grew more heated.
The press ratcheted up the rhetoric, too. The Wall Street Journal had been enthusiastic about cold fusion since the very beginning. Its reporter, Jerry Bishop, had written a page-1 story covering the Pons and Fleischmann press conference in Utah, and the Journal had become the go-to place for optimistic news about cold-fusion developments. When criticism of Pons and Fleischmann began to bubble through the press, especially the liberal press, the Journal struck back. In April, the New Republic wrote a piece blasting the scientists for releasing the experimental results “in a way that maximized publicity but defied the conventions that are supposed to ensure the reliability of scientific information.” The Wall Street Journal replied with a caustic editorial linking criticism of cold fusion with other complaints of East Coast liberals: “The pace of scientific advance is sometimes hard to discern amid the unending wail about trade deficits, food chemicals, the ozone layer, the greenhouse effect, animal rights or political ethics,” it declared. “Even within the scientific enterprise, the creative impulse of a Fleischmann and Pons must contend today with what might be called ‘Academy mentality.’”
Sun in a Bottle_The Strange History of Fusion and the Science of Wishful Thinking Page 15
