by Ray Monk
As Serber remembers it, the first guards at the site were Spanish American construction workers who were ‘dragooned to man the gate’. After that, the army took over ‘and brought in MPs who were mostly ex-New York cops and put the New York cops on the horses – probably none of them had ever seen a horse before – and set them to patrolling the fences’. Unsurprisingly, ‘they called that off after a couple of weeks’.
Serber also remembers taking part in a plan, devised by Oppenheimer and army security, to spread false rumours about what was happening at the Mesa. The rationale behind this is given in a letter from Oppenheimer to Groves, dated 30 April 1943. ‘We propose,’ Oppenheimer wrote:
that it be let known that the Los Alamos Project is working on a new type of rocket and that the detail should be added that this is a largely electrical device. We feel that the story will have a certain credibility; that the loud noises which we will soon be making here will fit in with the subject and that the fact, unfortunately not kept completely secret, that we are installing a good deal of electrical equipment, and the further fact that we have a large group of civilian specialists would fit in quite well.
What struck Oppenheimer as a credible plan, however, turned out, in practice, to be a laughable failure. Together with others from the laboratory, Serber was instructed to go to a bar in Santa Fe and start talking in a loud voice about the electric rocket they were working on. The problem they encountered was that, no matter how loudly they discussed it, no one seemed very interested. Eventually Serber approached a drunk at the bar and said to him: ‘Do you know what we’re doing at Los Alamos? We’re building an electric rocket!’ It was, Serber admits, mission unaccomplished: ‘the FBI and Army Intelligence never reported picking up any rumors about electric rockets’.
Equally unsuccessful was another idea Oppenheimer came up with to mislead potential snoops, this time involving Wolfgang Pauli, who since 1940 had been a physics professor at Princeton. Oppenheimer’s idea, he told Pauli in a letter written in May 1943, was one ‘that I think deserves to be taken seriously, although I know that you will laugh at it’. It was that Pauli could use his ‘great talents for physics and burlesque’ by writing phoney articles on aspects of theoretical physics and publishing them under the names of, for example, Bethe, Teller, Serber and Oppenheimer, thus forestalling questions the enemy might have about why these top physicists had apparently stopped publishing any work and preventing them from drawing the obvious conclusion that, as Oppenheimer put it, ‘we are finding good uses for our physicists’.
In his reply, Pauli reported that he was having problems getting funding for his research from the Rockefeller Foundation and the director of the Institute for Advanced Study, and so, though he ‘would be glad to be helpful in the suggested way’, he felt compelled to publish what he was writing under his own name in order ‘to prove to the quoted money-givers that after all I am working on something for their money’, fearing, he added, ‘their sense for burlesque to be rather undeveloped’. In any case, Pauli wrote, he doubted the scheme would work, since why would the enemy not believe that ‘the persons whose names figure as authors are not occupied beside some scientific work also with war problems?’ And then ‘the whole Don-Quichotery would be in vain’.
Despite the suspicions of him entertained by Pash, de Silva and other security officers, then, Oppenheimer seemed, on the face of it, wholeheartedly – if sometimes quixotically – in support of the security efforts of army intelligence. In this, as Lansdale pointed out, he stood out among his fellow scientists, some of whom, like Serber, adopted an attitude of amused disdain towards the security restrictions, while others were openly contemptuous and provocative. As he has recounted in his famous public lecture, ‘Los Alamos from Below’, chief among the latter was Richard Feynman.
Feynman was among the first to arrive at Los Alamos, being part of what Oppenheimer described as a ‘job lot’ of scientists from Princeton who came with Robert Wilson. He would later win the Nobel Prize and become one of the best-known physicists in the world, but in 1943 Feynman was a young man of twenty-four who had only just completed his PhD thesis. Though young, he had already impressed many of the most eminent scientists in America with the sharpness of his intellect and the originality of his mind – Wilson at Princeton and Teller at Chicago among them – and was very shortly to make a deep impression on Hans Bethe at Los Alamos. To the security staff at Los Alamos, however, Feynman was a mischievous and vexatious nuisance.
From the very beginning, Feynman was determined to cock a snook at the precautions he was asked to adopt. All the physicists at Princeton had been told not to buy their train tickets to Albuquerque, New Mexico from Princeton, since it was a small station and, if everyone bought tickets to Albuquerque from there, suspicions would be aroused. ‘And so,’ Feynman later said, ‘everybody bought their tickets somewhere else.’ Everyone, that is, except Feynman, ‘because I figured if everybody bought their tickets somewhere else . . .’
Once at Los Alamos, Feynman discovered to his horror that his letters to his wife, and hers to him, were being examined and, at times, censored. His wife, on learning this, repeatedly mentioned in her letters to him that she felt uncomfortable knowing that the censor was looking over her shoulder as she wrote. This led to Feynman receiving a note: ‘Please inform your wife not to mention censorship in her letters.’ But, of course, as Feynman gleefully pointed out, he himself was under instructions not to mention censorship, so he wrote back: ‘I have been instructed to inform my wife not to mention censorship. How in the heck am I going to do it?’ Feynman was presented with another opportunity to be a thorn in the side of the security effort when he discovered that the workmen on the site had cut themselves a hole in the fence, so as to enable them to leave for home without having to go through the official gate. So Feynman went out through the gate, walked around to the hole, came back in and then went out again through the gate, ‘until the sergeant at the gate began to wonder what was happening. How come this guy is always going out and never coming in?’
In the memoirs of the scientists who worked at Los Alamos, the pervasive presence of the army and the security measures they imposed are almost universally prominent. Apart from the extraordinary location, the fact that the laboratory was a military establishment was, in the eyes of the civilian scientists – most of whom would have had little or no prior experience of being with soldiers and working under army regulations – its most novel and noteworthy aspect. For many of these scientists, Groves was the very embodiment of everything they found strange, irksome and idiotic about the army. As such, he often appears in scientists’ recollections of Los Alamos as a figure of fun, a man whose limited understanding of physics and brutish manner made him a legitimate target of derision. Edward Teller, for example, though claiming to have ‘neutral’ feelings about Groves (and therefore, he emphasises, better feelings about him than most of the scientists at Los Alamos), remarks that Groves’s opening speech to the scientists ‘seemed about what would be expected from a person who knew nothing about the project he was supervising’. Teller says that he was puzzled to hear that Groves had complained about Hungarian being spoken on the site, since he and his wife were at the time the only Hungarians there and had spoken Hungarian only in their own apartment. Then he discovered that Groves had heard Felix Bloch’s sons speaking in their Swiss German dialect and ‘had confused that strange language with one even more peculiar’.
The task of maintaining good relations between the scientists and the military officers fell to the associate director of the laboratory, Edward Condon. In his autobiography, Groves goes so far as to say that maintaining good relations was Condon’s ‘major responsibility’. Whether or not it was his principal task, it was certainly a difficult and thankless one, made much worse by the fact that Condon and Groves very quickly developed extremely poor opinions of each other (‘Condon was not a happy choice,’ Groves remarks dismissively). The biggest issue on which they failed to see
eye-to-eye was ‘compartmentalisation’, the policy – which Groves regarded as ‘the very heart of security’ – according to which workers on the Manhattan Project knew only what they needed to know in order to do their jobs and no more. The workers at Oak Ridge and Hanford, for example, did not know that they were helping to produce uranium and plutonium, nor did the workers at one site even know of the existence of the other. It was this policy that had resulted in the strange situation mentioned earlier, of the FBI investigating breaches to the security of a project the existence of which they were officially unaware. Groves felt strongly that this policy should apply also to scientists, so that those working at the Met Lab at Chicago, for example, should know nothing about what was going on at Los Alamos.
Condon thought this was ridiculous and fundamentally incompatible with the successful pursuit of science. The issue came to a head towards the end of April, just six weeks after Oppenheimer and Condon had moved to Los Alamos, when Oppenheimer flew to Chicago to discuss the schedule for plutonium production with Arthur Compton. Groves was furious and, on Oppenheimer’s return, stormed into Oppenheimer’s office to make his feelings known to both Oppenheimer and Condon. Condon stood up to Groves and defended this breach of compartmentalisation, but was puzzled to see that Oppenheimer was not supporting him. A few days later, Condon resigned, giving his reasons in a long letter to Oppenheimer. ‘The thing that upsets me most,’ he told Oppenheimer, ‘is the extraordinary close security policy.’
I do not feel qualified to question the wisdom of this since I am totally unaware of the extent of enemy espionage and sabotage activities. I only want to say that in my case I found that the extreme concern with security was morbidly depressing – especially the discussion about censoring mail and telephone calls, the possible militarization and complete isolation of the personnel from the outside world. I know that before long all such concerns would make me so depressed as to be of little if any value.
He was, he said, ‘so shocked that I could hardly believe my ears’ when Groves reproached them for discussing technical questions with Compton: ‘I feel so strongly that this policy puts you in the position of trying to do an extremely difficult job with three hands tied behind your back that I cannot accept the view that such internal compartmentalization of the larger project is proper.’
So alien did this way of thinking strike Groves that he was convinced Condon had kept the real reason for his resignation quiet. ‘The considerations he cited in his letter of resignation,’ Groves said of Condon, ‘did not seem to justify his departure.’ His own impression, he went on, was that Condon was ‘motivated primarily by a feeling that the work in which we were engaged would not be successful, that the Manhattan Project was going to fail, and that he did not want to be connected with it’. As far as I am aware, there is no evidence in anything Condon wrote or said to support Groves’s interpretation of his reasons for leaving the project.
During his brief time at Los Alamos, Condon made at least one important and lasting contribution, not only to the work of the laboratory, but also to the physics of atomic-bomb manufacture, and that was his writing up and editing of Robert Serber’s introductory lectures, which formed The Los Alamos Primer (the title was Condon’s), a copy of which was given to every scientist on their arrival. There are several references among the memoirs and histories of Los Alamos to the fact that Serber was not a particularly good lecturer, but in print the lectures present a masterfully lucid account of bomb physics, some of the credit for which must go to Condon.
There were five lectures, the first of which was given on 5 April 1943, and the last on 14 April. The first lecture begins with the admirably clear and forthright statement: ‘The object of the project is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast-neutron chain reaction in one or more of the materials known to show nuclear fission.’ Actually, from a security point of view, in its use of the word ‘bomb’, this statement was a little too clear. ‘After a couple of minutes,’ Serber later recalled, ‘Oppie sent John Manley up to tell me not to use that word. Too many workmen around, Manley said. They were worried about security. I should use “gadget” instead.’ The word ‘gadget’ stuck and became the one everyone at Los Almos used to refer to the thing they were designing and manufacturing.
After spelling out the purpose of the project, Serber’s lectures go on to summarise the current state of knowledge regarding all aspects of bomb physics, much of which had remained unpublished and was therefore news to anyone not previously involved in the atomic-bomb project. He begins with a discussion of the fission process itself, emphasising that the energy release in fission is, per atom, more than ten million times that of an ordinary combustion process, such as that of a fire or a chemical explosion. Serber then explains the phenomenon of a chain reaction and says that it would take eighty generations of reactions to fission one kilogram of U-235. Those eighty generations would take place in 0.8 microseconds (a microsecond being one-millionth of a second), producing an explosion equivalent to 20,000 tons of TNT.
The lectures next provide a summary of what was then known about the physics and chemistry of the relevant materials, U-238, U-235 and Pu-239, and explain how plutonium is produced from uranium by a series of nuclear reactions. The calculations required to estimate critical mass are given and explained, and are used to provide a basic figure of 200 kilograms for U-235, which, Serber explains, ‘more exact diffusion theory’ developed at Berkeley in the summer of 1942 brought down to 60 kilograms. When a tamper is used to reflect back neutrons that would otherwise escape, Serber goes on, the critical mass for U-235 would possibly be as low as 15 kilograms, and for Pu-239 lower still. But, he was at pains to emphasise, all this was, in the spring of 1943, theoretical and uncertain. A large part of the task facing the laboratory was to provide experimental data upon which more reliable and accurate calculations could be made:
To improve our estimates requires a better knowledge of the properties of bomb materials and tamper: neutron multiplication number, elastic and inelastic cross sections, overall experiments on tamper materials. Finally, however, when materials are available, the critical masses will have to be determined by actual test.
In a section headed ‘Damage’, Serber demonstrated just how much scientists already knew about the devastation that an atomic bomb would cause. ‘Several kinds of damage will be caused by the bomb,’ he stated. First, there would be the damage from neutron radiation, which he estimated to be effective within 1,000 yards of the explosion. In notes that Serber added in 1992fn48 to the published version of The Los Alamos Primer, he says that in 1943 he had ‘overlooked a more serious source of lethal radiation’, namely the release of extremely energetic gamma radiation, the range of which, for the Hiroshima bomb, was 4,000 feet. Second, there is the damage caused by the blast or shock wave. Serber estimates that a bomb equivalent to 100,000 tons of TNT would have a destructive radius of about two miles. Other topics covered by his introductory lectures included the efficiency of the explosion (the proportion of the material that is actually fissioned before it all expands and blows apart), the possible methods of detonation and the various techniques of assembly.
The very last thing Serber dealt with in these lectures, under the heading ‘Shooting’, was the question of how the bomb was to be ‘fired’ – how, that is, the subcritical pieces of fissionable material (uranium or plutonium) were to be brought together to form a supercritical mass. The first method he considered was the simple mechanism envisaged by Frisch and Peierls in their memorandum, in which a small ‘bullet’ of the material is fired into a subcritical mass, thus making it supercritical. This had the advantage of being very straightforward, but the disadvantage of posing enormous ordnance problems, namely those of designing and manufacturing a ‘gun’ capable of firing the ‘bullet’ sufficiently quickly to prevent the bomb fizzling before it exploded. Another method discussed by Serber was the ‘implosion’ method, whi
ch was eventually used in the world’s first atomic-bomb explosion in July 1945. In this method pieces of the material are arranged in a circle and then brought together very quickly.
Though it has long been associated with Seth Neddermeyer, implosion was not invented by him, but rather by Richard Tolman, who suggested it at the Berkeley conference in 1942. Tolman and Serber collaborated on a memorandum on the subject at that time and, when urged by Conant and Bush to pursue the method in March 1943, Oppenheimer replied: ‘Serber is looking into it.’ In Oppenheimer’s original organisational chart of Los Alamos, the investigation of implosion was one of the things that was earmarked as Serber’s responsibility. Neddermeyer, however, became an enthusiastic advocate of the idea after hearing Serber’s lecture, and immediately dedicated himself to its development.
Neddermeyer’s development of the implosion concept was presented to the other scientists at Los Alamos at a major ten-day conference that began the day after Serber’s lectures finished. From 15 to 24 April, while the laboratories were still being built and the infrastructure of the growing town of Los Alamos was still being developed, an extraordinary collection of the best scientists in America – both native Americans and émigrés, those now working on the programme and those still working at their own universities – met to discuss the scientific questions that needed to be answered if an atomic bomb was ever going to be built.
On the first day of the conference, Oppenheimer, covering some of the same ground as Serber, summarised the present state of knowledge. With regard to the production of fissionable material by the enormous plants being constructed at Oak Ridge and Hanford, he told his audience that he estimated that from early 1944 100 grams of uranium-235 and, a year later, 300 grams of plutonium could be shipped every day. Oppenheimer also discussed the ‘Super’ that had so captured Teller’s imagination the previous summer, but insisted that it was at a much earlier stage of development than ‘the gadget’ and, as such, of decidedly secondary importance. On the two subsequent days Manley laid out the details of the forthcoming experimental programme, and Bethe discussed the physical constants that needed to be discovered, such as the critical mass, the number of neutrons emitted per fission, the various cross-sections and the efficiency of the explosion. On day four Serber led a discussion on the tamper. The issues covered in subsequent discussions included: experimental methods, the properties of natural uranium, detonation by gun method, the chain reaction produced by ‘the pile’ at Chicago, and, finally, the ways in which the critical mass, timescale and damage of the bomb might be discovered experimentally.