The First War of Physics (17 page)

After three meetings with Kremer over six months, Fuchs was passed to another agent, known to him only as Sonja. This was, in fact, Ruth Beurton, née Kuczynski, Jurgen’s sister. Living in Kidlington, near Oxford, with a British husband, Ruth Kuczynski had no formal association with the Soviet embassy and was therefore less likely to attract unwanted attention from MI5. They arranged to meet in Banbury, a quiet market town between Birmingham and Oxford.

Meddling foreigners

‘If Congress knew the true history of the atomic energy project,’ said Leo Szilard after the war, ‘I have no doubt that it would create a special medal to be given to meddling foreigners for distinguished services, and Dr Oliphant would be the first to receive one.’

American work on nuclear fission had continued to stumble forward through the winter of 1940–41, but the programme was languishing. Research was under way at various institutions on the theory of fission reactions, isotope separation, the properties of element 94, nuclear reactors and the production of heavy water. But none of this work was directed towards any kind of war objective.

NDRC funds were being used to study separation of U-235 by gaseous diffusion at Columbia University, by high-speed centrifuge methods at the University of Virginia, and by electromagnetic methods of the kind that Nier had used on a small scale in Minnesota to obtain tiny quantities of the isotope. Nier concluded that the electromagnetic method would be unsuitable for separation of U-235 on a large scale but Lawrence saw an opportunity to put one of his redundant cyclotrons to good use. The electromagnetic separation method and the working principles of the cyclotron are very similar, and Lawrence used NDRC sponsorship to investigate the possibility of converting the 37-inch cyclotron at the Rad Lab into a large mass spectrometer for isotope separation.

Bush remained determinedly sceptical of the prospects for progress towards a bomb, and much of the high-level discussion centred around the use of nuclear fission as a means of generating power. On 17 March 1941 Lawrence decided to agitate. Conant had just returned from a visit to Britain, a visit which had afforded him an opportunity to discuss nuclear fission with a number of MAUD Committee physicists. These discussions had opened his mind to the possibility of a bomb, but he had simply assumed that when Bush was ready to hear about what the British had to say, he would go through the proper channels. Lawrence thought the time had come to ‘light a fire under the Briggs Committee’. He asked Conant to pass on the message of frustration to Bush.

When Bush met with Lawrence two days later, Bush let him have both barrels. It was he who was running the show, he claimed, and he would back Briggs and the Uranium Committee unless there was a strong case for getting personally involved. In truth, Bush was still puzzled by the science,
and he feared the possibility of spending great sums of money without a clear end result. He decided to turn to the National Academy of Sciences for help.

Bush asked the National Academy for an ‘energetic but dispassionate review of the entire situation by a highly competent group of physicists’. In April 1941 the Academy in turn asked Nobel laureate Arthur Compton to head the review group. Compton was a respected physicist whose work on the absorption and scattering of X-rays and gamma rays had led him to discover the ‘Compton effect’,
⁵
but he was not a nuclear physicist. Having initially expressed doubts about his own fitness for the role, he quickly and eagerly accepted. Lawrence was also appointed to the group, along with physicists John C. Slater and John H. Van Vleck.

Should further impetus have been needed, it arrived in the form of Houtermans’ warning. On his arrival in America, Reiche had passed the message to Rudolph Ladenburg at Princeton. Ladenburg invited a number of distinguished physicists to dinner so that Reiche could repeat the message. Within this group, only Wigner was involved with the Uranium Committee and he made no comment. When, a few days later, an opportunity arose to alert Briggs himself, Ladenburg did so. Briggs expressed deep concern, asked that he be given any further information and promptly buried the matter in his files.

In the end, Compton’s review group needed three tries to get the story straight. The group submitted its first report on 17 May. It reflected Briggs’ conservatism, focusing on the promise of the controlled release of nuclear energy which would require years of development. No firm recommendations were made about the possibility of a bomb, but the report did suggest that any such weapon could not be expected before 1945. There was nothing at all in the report about fission of U-235 by fast neutrons, critical mass or bomb mechanisms.

Meanwhile, the prospects for a bomb based on element 94 were improving considerably. Glenn Seaborg was the son of Swedish immigrants (his father’s surname, Sjöberg, had been anglicised on Ellis Island). Born in Michigan, Seaborg had studied chemistry at the University of California, Los Angeles (UCLA) and had completed his doctorate at Berkeley, where he had become interested in the chemistry of radioactive substances. After hearing of Hahn and Strassman’s discovery, he was inevitably drawn to the study of uranium, and the new elements 93 and 94. Together with his graduate student Arthur Wahl, he had succeeded in separating a microscopic amount of element 94, a discovery he had wanted to shout from the rooftops, but which he had instead quietly filed with the Uranium Committee and the editor of
Physical Review
for publication after the war.

At first Seaborg did not give the new element a name, referring to it in conversation using the codename ‘copper’. When subsequent experiments required the use of real copper, the physicists had to refer to it as ‘honestto-God copper’, to distinguish it from element 94.

The Berkeley scientists immediately began work to investigate the fission properties of the new element. McMillan had left Berkeley in November 1940 to work on radar at MIT.
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So Seaborg and Emilio Segrè continued to use the 60-inch cyclotron to produce quantities of element 94 so that its fission properties could be measured. On 18 May they recorded a slow-neutron fission rate for element 94 that was nearly twice the comparable rate for U-235. There could now be no doubt that element 94 would be a suitable active material for an atomic bomb.

Bush was busy reorganising the structure and management of government-funded science. The NDRC was appropriate for managing laboratory research efforts but had no authority over the kind of engineering effort that would be required to translate scientific research into armaments. He proposed to establish a new agency, the Office of Scientific Research and Development (OSRD), with executive authority over the NDRC and any engineering projects resulting from its work. Bush proposed himself as chairman of the OSRD, reporting directly to Roosevelt. Conant replaced him as chairman of the NDRC.

The Nazis launched their invasion of the Soviet Union on 22 June, forcing the pace still further and changing the status of a decision on the future of the American fission programme from ‘urgent’ to ‘desperately urgent’. Conant decided that the review group needed an injection of engineering pragmatism, and engaged the services of engineers from General Electric, Bell Laboratories and Westinghouse. But their second report, delivered on 11 July, was another step backwards. The prospects for nuclear power were again positively evaluated, but there was hardly any mention of element 94, or a bomb.

Compton, who had been in South America at the critical time, feared that the government might abandon fission studies altogether. Lawrence had missed the meeting at which the report had been drafted because his daughter Margaret had been ill. He decided to draft a separate letter to the review group spelling out the importance of element 94. ‘If large amounts of element 94 were available,’ he wrote, ‘it is likely that a chain reaction with fast neutrons would be produced. In such a reaction the energy would be released at an explosive rate which might be described as a “super bomb”.’

Bush received an unofficial copy of Thomson’s draft of the MAUD Committee report shortly before it had been approved in July. This led to some high-level discussions and a slightly greater sense of urgency, but it appears that Bush resolved to wait until he had received a copy of the report through official channels before taking any further action.

Enter Oliphant.

It had become transparently clear that Britain could not possibly contemplate building an atom bomb on its own. The country lacked the money and the resources for the job and despite the fact that Germany’s attentions had turned eastward, Britain remained a nation under siege. Oliphant flew to America in late August 1941 to find out what was happening and, if necessary, stir things up.

He found that the MAUD Committee report had been passed to Briggs and that ‘this inarticulate and unimpressive man had put the reports in his safe and had not shown them to members of his Committee’. Oliphant was
greatly distressed. When he met with members of the Uranium Committee he talked openly and persuasively about the possibility of a bomb. At least one member of the Committee was shocked. Oliphant had come to the meeting and ‘said “bomb” in no uncertain terms … I thought we were making a power source for submarines’, he said.

Oliphant met Lawrence in Berkeley on 21 September. Lawrence drove them up Charter Hill, to the construction site where the 184-inch supercyclotron was being built. Oliphant summarised the MAUD Committee report and Lawrence enthused about electromagnetic separation of U-235 and the fission properties of element 94. Back in Lawrence’s office, they were joined by Oppenheimer, who heard for the first time about the tentative steps now being planned to build an atomic bomb.

Oliphant had further, unsatisfactory, meetings in New York with both Conant and Bush, and left to return to Britain wondering if his visit had had any real impact. He need not have worried. Lawrence was now fully committed. He contacted Compton, telling him that he now believed that an atomic bomb could be built that might determine the outcome of the war. Compton suggested they both meet with Conant a few days later at the University of Chicago’s 50th birthday celebrations, at which both Lawrence and Conant were due to receive honorary degrees.

They met at Compton’s house. Lawrence summarised the British work, the results on element 94 and the prospects for separating U-235. He expressed his dissatisfaction with Washington’s complacency in the face of compelling evidence of German interest in atomic energy. Conant’s initial reluctance gave way to conviction as Compton rallied to the cause. Then Conant turned to Lawrence: ‘Ernest, you say you are convinced of the importance of these fission bombs’, he said. ‘Are you ready to devote the next several years of your life to getting them made?’ Lawrence’s jaw dropped, but he did not hesitate. If Conant told him this was his job, he would do it.

Bush received an official copy of the MAUD Committee report on 3 October 1941, two weeks after its content had been discussed in Moscow. Bush took the report to Roosevelt on 9 October. America, criticised for its policy of isolationism, was not yet at war. Yet when presented with the
evidence that an atomic bomb was possible within the likely timeframe of the war in Europe, Roosevelt committed to action, without consulting Congress. He also reserved the matter of nuclear policy for himself and a small group of advisers, later to become known as the Top Policy Group, consisting of Bush, Conant, Vice President Henry Wallace, Secretary of War Henry L. Stimson and Army Chief of Staff George C. Marshall.

A third report was requested from the National Academy review group. Conant asked his Harvard colleague, chemist and explosives expert George Kistiakowsky, to participate. With Compton’s blessing, Lawrence asked Oppenheimer to support the theoretical work. Compton had known ‘Oppie’ for fourteen years and was glad to receive his helpful suggestions.

Compton presented the third, and final, report personally to Bush on 6 November 1941. Like the MAUD Committee report, this was now unequivocal:

A fission bomb of superlatively destructive power will result from bringing quickly together a sufficient mass of element U-235. This seems to be as sure as any untried prediction based upon theory and experiment can be … The mass of U-235 required to produce explosive fission under appropriate conditions can hardly be less than 2 kg nor greater than 100 kg … The possibility must be seriously considered that within a few years the use of bombs such as described here, or something similar using uranium fission, may determine military superiority. Adequate care for our national defense seems to demand urgent development of this program.

The American physicists were much more conservative in their estimates than their counterparts in Britain, but their conclusions were broadly similar. In the rush to embrace U-235, element 94 had once again slipped off the radar. Bush delivered the report to Roosevelt on 27 November. Roosevelt in effect sanctioned a decision that had already been made.

A new committee, called the S-l Committee, was convened, reporting to Bush’s OSRD. Bush had thought to appoint Lawrence to chair this committee, but he had grown increasingly concerned about Lawrence’s
inability to work under strict secrecy – Conant had reprimanded him for telling Oppenheimer about the project without authorisation. In the event, Conant became chairman. Briggs was left in place as chairman of the S-l Section, devoted to physical measurements, and also served as a member of the S-1 Committee.

There appears to be no formal document signalling the decision to begin the American atomic bomb project, merely a short note on White House paper accompanying the returned report of the National Academy review group. The note is dated 19 January 1942 and reads: ‘V.B. OK – returned -I think you had best keep this in your own safe. FDR.’

Winter in Moscow

The German encirclement of Moscow stumbled to a halt on 15 November 1941, as a cold, hard frost bit deep into the mud. By the end of November it was snowing heavily and the temperature had dipped to minus 20° Celsius. Machinery froze. Without gloves, winter shoes and clothing thick enough to cope with a hard Russian winter, men froze too. Many froze to death. The Russians, however, did not.