Cockcroft, however, let the excitement get the better of him. On 5th September, a Thursday, he wrote to Edwin Plowden, chairman of the Atomic Energy Authority, telling him about the neutrons but saying he wasn’t yet 100% sure they were thermonuclear. Plowden inferred from this that the probability was high, though not quite 100%, and he wrote to the Prime Minister, Harold Macmillan, the following Monday to tell him so. But by then, Macmillan could read about it in the newspapers for himself.
Britain goes for the big time: the ZETA reactor at Harwell.
(Courtesy of UK Nuclear Decommissioning Authority)
Somehow, news of the existence of ZETA had leaked out to the press along with the suggestion that something important was afoot. The day after Cockcroft wrote to Plowden there was a session on thermonuclear fusion at the annual meeting of the British Association for the Advancement of Science in Dublin and reporters were there in force expecting a big announcement of results from ZETA. Even the Irish prime minister Éamon de Valera was in the audience. Cockcroft had lined up two speakers for the session: George Thomson and John Lawson, a theorist who had worked at Harwell but had recently moved on to other things. Cockcroft had given Lawson strict instructions not to give anything away. At a press conference following the talks the pair were grilled by the press about what was happening at Harwell. Many of the questions they declined to answer because of the secrecy rules they were bound to, which annoyed the eager reporters. Thomson did concede that he thought at least fifteen years would be needed to build a power-producing reactor.
The newspapers were full of stories about fusion the next day, many extrapolating wildly about the prospects of fusion power. The Financial Times reported that ZETA had been producing neutrons since mid August, though this hadn’t been mentioned at the Dublin meeting. Others said that ZETA had reached temperatures of 2 million °C. The more fanciful reports distressed the researchers at Harwell and Thonemann argued that they had to make an official statement to set the story straight. Cockcroft agreed but his hands were tied by the agreement with the US; any official statement would have to be approved by them too. A draft press release was drawn up and then cabled to Washington.
The first reaction from the AEC was to say that they would make a parallel announcement at the same time. But after US fusion scientists expressed scepticism at the British results, the head of the AEC, Lewis Strauss, said any announcements should wait until the next Geneva Conference on the Peaceful Use of Atomic Energy, a whole year away. Plowden would have none of it and they agreed to wait at least until the next meeting of Project Sherwood, the codename for American’s fusion programme, in mid October when visiting British scientists could explain their results. Plowden told Strauss he didn’t think he could hold off the British press any longer than that.
The Harwell team knew they needed more evidence, both of the plasma temperature and the thermonuclear nature of the neutrons, but Thonemann and others suspected that the Americans had an ulterior motive: they wanted more time for their own experiments to bear fruit so it would not look like they had been beaten in the fusion race. Harwell had to accept the delay, so the team continued to run ZETA, gather more results and look for firmer evidence.
At the beginning of October, however, two momentous events occurred which would load ZETA with enormous political baggage. On 4th October the Soviet Union launched Sputnik, the world’s first artificial satellite. Less than a week later, Pile 1, a nuclear fission reactor at Windscale in Cumbria, caught fire and spread radiation across the local area. Although the Windscale pile was designed to produce plutonium for nuclear weapons – not generate electricity – the fire and its threat to the population was a major blow to the clean high-tech image of nuclear power, and the public began to question its safety. The Atomic Energy Authority needed something to distract people from the fire. ZETA, with its cleaner and safer form of nuclear power, would do the job perfectly.
On the other side of the Atlantic, the United States was reeling in shock from the launch of Sputnik. The US had always assumed it had an unassailable lead in high technology and that the Soviet Union would forever be playing catch-up. In part this was because the US had captured all Nazi Germany’s top rocket scientists at the end of the war and spirited them back to America. The conquest of space was theirs for the taking, so they thought. While the launch of Sputnik was greeted with wonder by many, for the US military it inspired terror. If the USSR could launch a satellite, it could in theory drop a nuclear weapon from space onto anywhere on US territory – something for which America had no defence. The US needed some new breakthrough to show that it was still a technological powerhouse. Fusion could provide that breakthrough but the press might portray it as a British triumph, further humiliating the US. As a result, the AEC continued to play for time.
Every day that passed was torment for the members of the Harwell team who were desperate to tell the world about their achievement; especially since inquisitive newspapers were publishing ever-more speculative stories about what they thought was going on. This particular period of history, the 1950s, is perhaps unique in that scientists – and especially physicists – were treated as heroes. Although the nuclear weapons dropped on Japan had inflicted awful damage, creating them was a tremendous technical achievement and they had brought the war to a swift end. In the postwar years physicists served up more wonders: rockets, jet planes, televisions and nuclear power. On TV and in films they were portrayed as noble knights in white coats, able to solve almost any problem. In the uncertain world of the Cold War it was good to have such people on your side. And it was into this atmosphere that the Harwell team aimed to launch their reactor, which promised clean and virtually limitless power at very little cost. They were surely unprepared for the impact their announcement would make.
At the Project Sherwood meeting in October it was agreed that both teams would publish papers describing their results and the text of a new press release was hammered out, but the AEC continued to stall, arguing that more evidence was needed. Newspaper articles were beginning to carry claims that Britain was ahead of the US in fusion technology, and that Harwell’s ‘triumph’ was being suppressed because of US-imposed security rules. Questions were asked in Britain’s House of Commons. Before anti-US sentiments got carried away, Strauss agreed to go ahead with publication but first sent a delegation of US fusion scientists to Harwell to see ZETA for themselves. Following their visit in December, the US scientists still argued for more delay but it was agreed that both sides would publish scientific reports in the journal Nature early in the following year.
So it was that the press was invited to Harwell on 23rd January, 1958 and the researchers opened up Hangar 7 to show ZETA to the world. Because of their nagging doubts about the origin of the neutrons, the researchers didn’t put anything into the papers in Nature about how the neutrons might have been produced. The press release given out to reporters, however, suggested the neutrons were probably thermonuclear. Scenting that this was a key issue, reporters repeatedly asked the Harwell scientists about the neutrons but only got evasive answers. At the press conference that day Cockcroft was similarly bombarded with questions and eventually admitted that he was 90% certain that at least some of the neutrons were thermonuclear.
The next day, ZETA was the top story across the globe and Cockcroft’s 90% certainty was reported in every story. ‘The Mighty ZETA,’ trumpeted the Daily Mail’s front page. The News Chronicle declared, ‘Britain Unveils Her Sun.’ Many described ZETA as ‘Britain’s Sputnik.’ The Hangar 7 team were suddenly celebrities, with their pictures on the front pages alongside brief pen portraits, often focusing on their comparative youth. ‘These are the names which will be linked with the controlling of the H-bomb in the same way that Rutherford, Cockcroft, Fermi and others are bracketed with atomic energy,’ said the Mail, continuing, ‘Tall, dark and bespectacled, Thonemann has dedicated all his working years to tapping nature’s biggest bank of energy.’
The Italian
press gave ZETA more coverage than it had Sputnik. French papers were some of the few that pondered the 10% possibility that Cockcroft was wrong. The New York Times reported the view of one researcher that fusion reactors could power spacecraft. Newsreel cameras recorded the open day at Hangar 7 and a hastily produced TV programme explained the breakthrough to Britain’s viewing public. Despite the simultaneous papers published in Nature, few reports mentioned the work being done in the US – ZETA was a very British triumph.
ZETA and its creators continued to be feted in the months that followed, but researchers were still concerned about whether they really were seeing what they thought they were seeing. Other pinch-based machines were also starting to produce neutrons, including a torus built by Ware at AEI and America’s whimsically named Perhapsatron. But US scientists continued to be sceptical about ZETA’s results. They just didn’t believe that it could be getting up to the temperature of 5 million °C that the Harwell team was claiming, and any less than that would not be hot enough to cause thermonuclear reactions.
The questionable neutrons were about to come under close scrutiny. At the ZETA press conference in January, Basil Rose, a nuclear physicist from another section at Harwell, managed to get in to find out what all the fuss was about. Rose was in charge of Harwell’s cyclotron, a particle accelerator that shared Hangar 7 with ZETA. He quickly realised that finding out more about the neutrons was crucial, and his experiment had a detector that could measure accurately the energy and direction of neutrons. Frustratingly, he had just leant the detector, called a diffusion cloud chamber, to scientists at University College London but they hadn’t started using it yet and Rose persuaded them to ship it back to Harwell.
Peter Thonemann (left) receives an achievement award from Sir Edward Hutton (right). Sir John Cockcroft looks on.
(Courtesy of UK Nuclear Decommissioning Authority)
If ZETA’s plasma was at thermonuclear temperatures, then the deuterons would be bouncing around in random directions, colliding and fusing. The neutrons they emitted would therefore be flying out in all directions equally and with similar energies. When Rose hooked up his cloud chamber to ZETA and studied the neutrons, this was not what he found. The neutrons were mostly emitted in line with the axis of the plasma current and more strongly in one direction than the other. To prove the point, Rose got the team to run ZETA ‘backwards,’ with the plasma current flowing in the opposite direction to normal. Sure enough, the preferential direction of the neutrons was reversed. The conclusion: ZETA’s neutrons were definitely not created by thermonuclear fusion.
In mid May the team announced these results at a press conference in London and a month later Nature published the details. Press reaction was sober and relatively restrained. Perhaps newspapers were embarrassed by their own wild extrapolations a few months previously. The Manchester Guardian mused over whether the obsession with secrecy was to blame:
In a huge research project like that revolving around ZETA the day-to-day rubbing of shoulders with scientists of other specialities is the best safeguard of sound analysis and interpretation … So it will inevitably be asked whether things might not have gone differently if the members of the ZETA team had been allowed to talk freely and informally to other scientists.
Fusion scientists always maintain that ZETA was a success. It was, after all, the first machine to achieve a large, stable pinched plasma at high temperature. Scientists at Harwell continued to use it up until 1968, garnering much useful information. But in the public mind ZETA will always be remembered as a failure: British scientific hubris dashed upon the rocks of a problem more complex than foreseen. It’s true that the Harwell team were impetuous in going public with their results when they had very unreliable information about the temperature of the plasma and the nature of the neutrons, but they are not solely to blame for the mess that ensued. The need for a success after the shock of Sputnik and the Windscale fire meant that Harwell was under enormous political pressure to produce the goods.
Britain was also hungry for something to restore its national pride. Although it had emerged as one of the victorious powers at the end of the war, it was struggling to hold onto its seat at the top table. Britain had had to scramble to catch up with the superpowers in atomic power and weapons. Its economy was in tatters (rationing had only ended in 1954) and its empire, which had once spanned the globe, was being rapidly dismantled. In 1956, Britain’s adventure with the French to seize control of the Suez Canal following nationalisation by Egypt was humiliatingly squashed by a disapproving US. With so little to celebrate, the British public embraced the scientists who had given them a world lead in this wonderful new technology, and felt betrayed when it was taken from them again.
A few months after the climb-down over ZETA, British fusion scientists, along with colleagues from all over the world, gathered in Geneva for the second ‘Atoms for Peace’ conference which this time was focused on fusion. Just before it began all sides declared they would declassify their fusion research. The US and Soviet fusion programmes vied to outdo each other in displays of research activity. The US stand cost millions to put together and contained four real fusion machines. The Soviets put on a similar show. With the veil of secrecy lifted, Harwell’s researchers could see that they wouldn’t be able to keep up for long.
In 1960 Britain’s fusion researchers began moving to a new purpose-built laboratory at Culham, another former airfield some 10 kilometres from Harwell. The plan for a bigger and better ZETA 2 was abandoned, however, and the emphasis shifted to smaller machines to gain a better understanding of how plasma works. Thonemann left the programme and, in a sense, the ‘heroic age’ of British fusion was at an end. It would be some decades before another big fusion reactor was built in the UK but, elsewhere, things were just hotting up.
CHAPTER 3
United States:
Spitzer and
the Stellarator
WINDING THE CLOCK BACK TO 1951, WHEN THONEMANN was already installed at Harwell, the United States didn’t even have a research programme into controlled nuclear fusion. Just after the war, some of the scores of scientists who had been holed up in the Los Alamos laboratory for the Manhattan Project starting turning their minds to other things, in particular how to build a more powerful nuclear bomb based on the fusion of hydrogen, the H-bomb or ‘Super’ as scientists called it at the time. Enrico Fermi, who had built the first ever nuclear fission reactor – Chicago Pile 1 – in 1942, came to the lab and gave a series of lectures on thermonuclear reactions. This got some of his audience thinking about controlling fusion for energy production. During those days at Los Alamos, Edward Teller would organise ‘wild ideas’ seminars and some of those were devoted to the problem of how to control fusion reactions. Briton James Tuck and Polish mathematician Stanislaw Ulam did some calculations on the possibility of accelerating beams of deuterium ions to high energy and colliding them to cause fusion. They even carried out some experiments but the effort fizzled out. Now that the wartime bomb project was finished, many scientists at Los Alamos were drifting back to their prewar jobs. Teller, for example, returned to the University of Chicago and Tuck went back to the Clarendon Laboratory in Oxford.
Things changed following the explosion of the first Soviet atomic bomb in August 1949. US strategists had believed they had many more years before the Russians caught up with their nuclear programme. The blast at Semipalatinsk was a wake-up call. If the Soviets could produce a fission weapon in just a few years, an H-bomb based on fusion might soon follow. The US had to get there first, so President Truman ordered a crash programme to develop the H-bomb. Teller returned to Los Alamos in 1950 and many others joined the effort. At Princeton University in New Jersey a branch of the programme, known as Project Matterhorn, was set up to work on theoretical aspects of the H-bomb. One of those recruited to work on it was the astrophysicist Lyman Spitzer Jr. An astrophysicist might seem an odd choice but Spitzer was an expert on the interstellar medium, the thin clouds of g
as and dust that occupy the space between stars. Interstellar gas is mostly a hydrogen plasma and since the designers of the H-bomb knew they would have to master hydrogen plasma in their device, Spitzer was their man.
In March 1951, before Spitzer started on Project Matterhorn, he was due to take a skiing holiday in Aspen, Colorado. But on the morning of his departure he had a phone call from his father telling him that he should buy a copy of The New York Times. The paper reported that the Argentine dictator Juan Perón had announced that his country had achieved controlled nuclear fusion and was developing the technology to generate electricity for the benefit of all mankind. Details were few at the time but it was revealed later that an Austrian physicist called Ronald Richter had persuaded Perón in 1948 that he could provide Argentina with inexhaustible energy through fusion. Perón was an enthusiast for all things German and, without consulting Argentine physicists, essentially wrote Richter a blank cheque and built him a laboratory on the island of Huemul in a remote part of western Argentina. Richter’s plan was to use some form of magnetic field to confine a plasma and react deuterium and lithium. According to Perón’s statement on 24th March, Richter’s experiment, dubbed the thermotron, had produced particles and energy consistent with fusion.
Spitzer set off for Aspen but the news reports from Argentina had set his mind racing. If you wanted to, how would you achieve a controlled fusion reaction? Spitzer was a gifted scientist who had studied at Yale, Princeton and Cambridge (under Eddington) in the 1930s. He played a key role in the development of sonar during the war and in 1947, aged 33, he was made head of Princeton’s astronomy department and director of the Princeton University Observatory. He was something of a renaissance man – keen on music and an able mountaineer – but couldn’t resist the occasional wild idea, such as climbing up the tower of the Princeton graduate college with ropes and pitons, only to be arrested by the university’s security police. He cut something of an old-world figure with his upright bearing and courteous speech, but he was highly principled and always showed total independence of mind. Something that he could not resist, however, was a big and challenging scientific problem and controlled thermonuclear fusion fitted that bill perfectly.
Piece of the Sun : The Quest for Fusion Energy (9781468310412) Page 6