ZETA’s fall from grace a few months later shocked US scientists, even though some had doubted its results. The team at Los Alamos soon carried out similar tests on the Perhapsatron and Columbus to the ones that sank ZETA. Their machines too were shown to be producing spurious neutrons. That left Project Sherwood without a triumphant centrepiece for the Geneva conference. But Strauss was undaunted. He wanted neutron-producing devices whether the neutrons were thermonuclear or not. Strauss expected that no one at the meeting would be in a position to tell the difference and if the Soviets had a device spitting out neutrons and the US didn’t it would be a disaster. So he kept up the pressure on the American teams to get their exhibits ready.
Over the summer, dozens of researchers in all the fusion labs laboured over models and displays and tested working devices before boxing them up and despatching them to Geneva. In all, some 450 tonnes of equipment was shipped from the four Sherwood labs. (Oak Ridge National Laboratory’s previously small fusion research effort grew rapidly in the run-up to Geneva and it became a fully-fledged member of the project.) Whole airliners were chartered to carry Sherwood technicians and their families to Switzerland, some arriving more than a month early to get everything set up before the 1st September start of the meeting. The number of people registered to attend dwarfed the 6,500 hotel beds in Geneva, so some participants had to stay in cities such as Evian, 50 kilometres away.
The scale of the conference was huge. It was held in the Palais des Nations, built in the 1930s for the League of Nations but later home to the United Nations’ European headquarters. Its main assembly hall could hold around 2,000. In the grounds of the palace an enormous exhibition hall was specially built for the conference. Five thousand scientists from sixty-seven countries attended the meeting, along with 900 journalists and 3,600 observers from industry. The interested public could also look around the exhibition. Time magazine called it the ‘monster conference.’
While the US exhibit lacked the knockout display of fusion neutrons that Strauss had wanted, it was certainly impressive. Princeton had shipped over its Model B-2 stellarator and displayed mock-ups of the Model C and other devices; Oak Ridge had a model of its Direct Current Experiment (DCX) device; models of a mirror machine and linear pinches were on show from Livermore and Berkeley; and Los Alamos had a working Perhapsatron and a Columbus both producing neutrons, as was a variant of the pinch known as Scylla. Along with displays of fission reactors and other nuclear technologies, the US exhibit took up more than half of the exhibition space and registered 100,000 visitors. It had cost $4.5 million – a huge sum in 1958.
Two days before the conference opened both the US and the UK had announced total declassification of their fusion programmes. The scores of fusion researchers who had been working in secret laboratories in those countries and the Soviet Union emerged blinking into the light. They could present papers to a wide audience in the assembly hall and also had to deal with press conferences and curious members of the public. At a time when East and West were locked together in a Cold War, at Geneva you could see Russian and American scientists, heads together, earnestly discussing plasma physics in the conference corridors, or sitting on the grass in the palace gardens among the peacocks that lived there.
Despite the excitement generated by this entire new field of science suddenly revealed, the scientific presentations in the assembly hall had a more reflective tone. The disappointments earlier in the year with the pinch devices – ZETA, Perhapsatron and Columbus – along with the technical difficulties being experienced by other machines, had caused many to rethink their optimistic forecasts of a smooth progression from proof-of-principle to prototype to power reactor. Peter Thonemann told the assembled scientists:
To my mind, the problem of stability is of paramount importance. Unless the rate at which charged particles cross magnetic lines of force can be reduced to that given by classical diffusion theory, the loss of energy to the walls will prevent fusion reactions from becoming a practical power source.
I think that the papers to be presented at this Conference, and the discussions which follow them, will show that it is still impossible to answer the question, ‘Can electrical power be generated using the light elements as fuel by themselves?’
Edward Teller listed a number of hurdles that would have to be overcome, including the intense neutron radiation emanating from fusion reactions that changes the nature of the materials of the reactor and makes the reactor a no-go area for human operators.
These and other difficulties are likely to make the released energy so costly that an economic exploitation of controlled thermonuclear reactions may not turn out to be possible before the end of the 20th century.
After two weeks of discussions, few scientists will have returned home from Geneva with any illusions about the difficult tasks facing them.
The Geneva conference marked something of a watershed for the US fusion programme. In June, just before the meeting, Lewis Strauss had stood down as head of the AEC, although he still led the delegation to the conference. He had not achieved his goal of seeing a successful demonstration of fusion power during his tenure, but he had taken a somewhat relaxed small-scale research programme involving a few dozen people (fiscal year 1954 budget: $2 million) and pumped it up into a dynamic development effort employing hundreds (1958 budget: $29 million).
The atmosphere of suspicion and competition between the US, UK and Soviet programmes, fuelled by the secrecy imposed on them, was diffused when the researchers from each side actually met, compared notes, and realised that they were all in the same scientific boat: desperately seeking a route to fusion energy while not really having a good enough grasp of how plasma behaves. The relationships forged at Geneva meant that, even while most scientific disciplines and most of normal life were divided into East and West, fusion research remained a truly international activity. Scientists were able to visit each others’ labs across the Iron Curtain relatively easily and international conferences brought them all together on a regular basis.
East-West links were far from the only changes to come from declassification. Overnight the researchers’ top-secret project became a normal scientific discipline. Princeton’s Project Matterhorn was renamed the Princeton Plasma Physics Laboratory. It became easier to hire new staff and to train new researchers. Princeton and the Massachusetts Institute of Technology set up graduate programmes in fusion research.
Fusion was absorbed into mainstream science. Researchers in closely related fields could now make inputs and attend fusion conferences, which broadened the available expertise. The American Physical Society set up a Division of Plasma Physics which held its own meetings. Specialist plasma physics journals were created and the papers submitted were subjected to ‘peer review’ so that they were vetted by other scientists. The effect of all these changes was to raise the scientific standards of fusion research; there emerged new levels of scrutiny and criticism that, if they had arrived earlier, might have tempered the unbridled optimism that surrounded ZETA, Columbus and the Perhapsatron.
Industry also got in on the act. Westinghouse, which had seconded two engineers to work on the design of Princeton’s Model C, let them remain there while keeping them on its own payroll. Thinking that fusion could one day rival fission energy, General Electric and the recently formed General Atomics both started up their own fusion research programmes.
Project Sherwood also had to face the new reality of its position within the AEC. Under Strauss’ tutelage, it had led a charmed existence with ever increasing budgets, because he had a special interest in fusion. The new AEC chairman, John McCone, had no such soft spot. In fact, for his first year in the post his attention was focused elsewhere, on fission reactors, nuclear-powered ships and his concern that a ban on nuclear testing might be imposed. But in July 1959 he ordered a review of Project Sherwood, in particular of its level of funding. Sherwood’s budget had been tripled in November 1957 to help the labs prepare for the Geneva confe
rence, and the lab heads were led to believe that this level of funding would continue after the meeting.
McCone had other ideas. The project should be funded, he felt, in line with its value to the AEC, just as any of its other research programmes were. He also could not understand why there were so many different fusion devices being studied. Why not just focus on the few most promising ones? The urgency of the project had also abated. While once it had looked a couple of steps away from a power-producing reactor, now it seemed more focused on the study of fundamental plasma physics. The Sherwood steering committee argued successfully for retaining all the different device types, but it did accept that a 10% cut in funding was inevitable.
Pinches fell from favour in the United States following the disappointments of Columbus and the Perhapsatron and hopes were pinned on the stellarator. Princeton’s Model B was produced in various versions (B-2, B-3) to correct magnet faults and add extra heating systems but all of them suffered from a problem that the scientists called ‘pumpout.’ Essentially, particles were drifting to the edge of the containment vessel faster than predicted by theory and taking heat out of the plasma with them.
Spiralling plasma particles can jump to another field line following a collision, and so diffuse across the field towards the vessel wall.
(Courtesy of EFDA JET)
In the simplest picture of plasma in a stellarator, particles are held in place by the magnetic fields, making tight spirals around the magnetic field lines. But this doesn’t take into account collisions between particles. When this happens particles can be bumped from one field line to another and so gradually drift across the lines. This process – diffusion – happens in all gases, but fusion researchers had counted on magnetic fields slowing it down. Theorists predicted that the rate of diffusion would decrease in line with the square of the magnetic field strength. So doubling the field strength cuts the diffusion rate by four. This situation, known as classical diffusion, was not what they saw in practice.
During the war, American physicist David Bohm had done some research on the diffusion of plasmas in magnetic fields as part of the Manhattan Project. He wanted to separate isotopes of uranium so that natural uranium could be enriched for use in atom bombs. Purely by experiment he found that diffusion across magnetic fields decreased in proportion with the field strength, not field strength squared. This relation was much less favourable for fusion reactors because increasing the field strength does not rein in diffusion so strongly. Builders of fusion machines in the 1950s didn’t think that Bohm’s formula applied to them because he had studied plasmas of much heavier ions, at lower densities and temperatures. Pumpout was causing them to have doubts. The team working with Model B-3 studied the rate of diffusion over a wide variety of magnetic field strengths and found they varied exactly in the way Bohm had seen.
In May 1961, after four and a half years of design and construction, Princeton completed the Model C stellarator. Its racetrack-shaped plasma vessel was 12m in length. Because of its larger size, the Model C held onto particles ten times longer than the Model B-3 had, but when researchers investigated the effect of increasing magnetic field strength, Bohm’s relation held sway rather than classical diffusion. Throughout the late 1950s and early 1960s, Bohm diffusion was the bane of fusion scientists’ lives. All they could do was go back to the drawing board, try to understand plasma better and see if they could find a way around the problem.
It was a bad time for the fusion programme to show signs of doubt. The shock of Sputnik’s launch in 1957 had prompted a huge hike in government spending on science and technology, but that was now being called into question. More specifically, it was more than a decade since the AEC started funding controlled fusion research and scientists had promised prototype power reactors by this time. Instead, money that was meant to be spent on developing a new source of energy was paying for basic research on plasma physics. In 1963 the US Congress trimmed $300,000 from the programme’s $24.2 million budget. The next year it was cut again to $21 million. Even within the AEC fusion had few supporters. The commission was more concerned with developing a fast breeder reactor, which seemed a better short-term prospect for energy production than fusion.
The end of the line: the Model C stellarator.
(Courtesy of Princeton Plasma Physics Laboratory)
In September 1965 fusion researchers from across the world gathered at the Culham Laboratory, the new home of Britain’s fusion programme, for a conference organised by the International Atomic Energy Agency. The IAEA had started the meetings to sustain the international cooperation begun at Geneva in 1958. The first had been at Salzburg in 1961 and now it was Culham’s turn. Spitzer gave a presentation summarising the results from all the toroidal machines worldwide. It was not an encouraging survey: all seemed to be failing either because of Bohm diffusion (the stellarators) or instabilities (the pinches). There was one potential bright spot piercing the gloom of Spitzer’s talk: Lev Artsimovich, the forthright and combative head of the Soviet fusion effort, described encouraging results from Russia’s variant on the toroidal pinch, known as a tokamak.
The tokamak takes its name from the Russian phrase toroidal’naya kamera s magnitnymi katushkami (toroidal chamber with magnetic coils). It has a plasma current driven around the torus by an electromagnet and so its plasma is pinched into a narrow band around the centre of the tube. Where it differs from other pinch devices is in the added longitudinal magnetic field directed around the ring. Such fields were added to the Perhapsatron and ZETA to help stabilise the plasma, but the tokamak’s longitudinal field was around 500 times stronger. This field, combined with the one produced by the plasma current, resulted in a field which twists in a helix as it moves around the ring – a magnetic corset holding the plasma in place. Artsimovich told his fellow scientists at Culham that the tokamak was proving capable of suppressing instabilities and that it was confining the plasma ten times longer than Bohm’s formula said was possible.
The Russians’ Achilles heel was their measurements, however. Their instruments were primitive and they couldn’t take readings of temperature and confinement time directly; instead they inferred them from other measurements. As a result, many at the meeting were sceptical of the seemingly huge advances that the Russians had achieved with the tokamak, sparking an acrimonious debate between Spitzer and Artsimovich. Spitzer said he felt deep pessimism for the future and many delegates wondered if instabilities and Bohm diffusion were inescapable properties of hot plasma.
In a tokamak, the horizontal toroidal field and vertical poloidal field combine to produce helical magnetic field lines.
(Courtesy of EFDA JET)
Back home in the United States, Spitzer was soon forced to make a difficult personal decision. While he had worked on fusion, he had retained his post as head of Princeton University’s astronomy department. But now the university asked him to become chair of its general research board. Three jobs seemed like too much. When Spitzer had devised the stellarator on the ski lifts of Aspen, he considered it a ten-year project to get to a prototype power reactor. Now, fifteen years on, the stellarator still had serious problems and prototypes were nowhere to be seen. Although some years earlier he had handed over administrative leadership of the lab to Melvin Gottlieb, he was still scientifically the heart and soul of the laboratory and could often be seen riding on his bike from Princeton to the lab along the historic Route 1 highway. So, in 1966, Spitzer stepped down from his post at the Princeton fusion lab and returned to his first love: astronomy. He went on to have a major impact in that field, devising some of the earliest orbiting space observatories and helping to get the Hubble Space Telescope off the ground. NASA’s Spitzer Space Telescope, launched in 2003, is named in his honour.
However, his former fusion colleagues now had to face a thorough review of the fusion programme ordered by the AEC. With the field seemingly in the doldrums and without direction, the review committee was asked to decide if it should be accelerated,
decelerated or killed. Members visited labs, heard presentations and debated the relative merits of different machines. The committee concluded that fusion research was worth preserving. It acknowledged that progress had been made and argued that if fusion proved possible, the US needed a cadre of qualified scientists to take advantage of it. It also argued that to lose the race for fusion to some other nation was on a par with losing the space race to the Russians. The panellists recommended that the budget for fusion be increased by 15% per year for five years, but the prospect of Congress agreeing didn’t look good.
The United States at the time was increasingly committed to the war in Vietnam and President Lyndon B. Johnson was trying to push through a set of domestic reforms known as the Great Society which aimed to tackle poverty and racial injustice with increased spending on education, medical care and urban problems. After much debate within the AEC, in Congress and in the White House, the AEC commissioners came up with a more modest proposal: the budget would rise by 15% in the first year followed by progressively smaller rises until it was boosted by around 6% in the fifth year. In addition, up to $4 million was to be budgeted each year for equipment.
With the stellarator struggling, researchers were still trying to find other more successful confinement schemes. Livermore and General Atomics were still working on mirror machines. At Los Alamos, Tuck and his team were developing a variation on the toroidal pinch called Scyllac. And General Atomics had also teamed up with the University of Wisconsin on an elaborate device called a multipole that showed good confinement but only at low density and temperature.
Piece of the Sun : The Quest for Fusion Energy (9781468310412) Page 9