by Craig Nelson
Robert Serber gave the introductory lecture to new arrivals at Los Alamos and, worried about omnipresent USED construction crews able to eavesdrop on every meeting, he called the Bomb “the gadget.” Serber estimated critical mass could be arrived at with fifteen kilos (thirty-three pounds) of uranium-235 or five kilos (eleven pounds) of plutonium-239, surrounded by a shell of ordinary uranium. In the two years it would take Hanford, Oak Ridge, and Chicago to amass that quantity of fissile ordnance, Los Alamos would have to design an atomic trigger. Dick Feynman: “All science stopped during the war except the little bit that was done at Los Alamos. And that was not much science; it was mostly engineering.”
The labors of the mesa were far more dangerous than any civilian knew. The MAUD report included an atom-bomb gun design, which fired a plug of uranium at a bowl of uranium. This would become Little Boy, used against Hiroshima, and was a very basic idea—U-235 molded into six-inch stackable washers with a four-inch hole in the middle that would fit a four-inch-round plug of the same, also made of disks. One design question was, how much of the rare and precious uranium would the Little Boy gun-style bomb need to work? In 1944, Otto Robert Frisch was assigned this investigation, and his method was, by any standards, hair-raising. In Omega Canyon, so remote as to result in as few casualties as possible if the worst happened, Otto built a small tower, the “guillotine,” which dropped plugs of uranium metal through blocks of uranium metal surrounded by tamper—the basic design for the Hiroshima bomb—which went supercritical for less than a second and immediately showed the quantity needed. Dick Feynman said it “was like tickling the tail of a sleeping dragon . . . as near as we could possibly go towards starting an atomic explosion without actually being blown up.” After testing with Frisch’s guillotine, the amount of each segment could be shimmed by adding additional washers of isotope. In the bomb, a gunlike explosion of cordite would unite the two and could be triggered by pressure or proximity fuse or just about anything else in the Pentagon trigger basket. Little Boy was easy to set off accidentally, such as by dropping it on its nose, so small studs were put in place that would be sheared away by the cordite blow. The design was so foolproof that Oppenheimer didn’t bother testing it before it was dropped over Japanese skies, and it was considered so dangerously easy for a foe to build that, after Japan’s surrender, the design files were destroyed in a Los Alamos bonfire.
In another experiment, Frisch was stacking cores of enriched uranium when he leaned over the pile, which he called Lady Godiva, to yell to an assisting grad student. The neutron counters’ red lights started up and did not fade, and Frisch realized that the water from his body and the reflection of his white lab coat were exciting Godiva’s neutrons. He swept his arm, throwing several blocks of Oak Ridge’s HEU onto the floor. Two seconds more, and he would have been dead.
One mesa family had a cat that developed a strange wound in its jaw that wouldn’t heal. Army vets realized that somehow it’d gotten contaminated and was losing bone to radiation; they kept it alive to see what would happen next, but after its hair fell out and its tongue swelled, the family asked that it be put down. Walter Zinn opened a can of thorium and it exploded, severely burning his hands and face. Herbert Anderson was drying radium on a hot plate when it began to burn; he rushed into the room to stop the destruction, and six years later he was diagnosed with berylliosis—the sweet-to-the-tongue but poisonous beryllium had deposited in his lungs. Los Alamos chemists developed a policy that, if cut skin came in contact with plutonium, “immediate high amputation” was necessary.
Research Division (R-Division) chief Robert Wilson: “The Critical Assemblies Group decided not to have the elaborate safety devices that were used, for example, with cyclotrons. Instead they decided to depend on their wits alone. . . . I was the crew member whose turn it was to help the single physicist who showed up. His equipment consisted of a small wooden table, a single neutron counter, and boxes containing the small cubes of enriched uranium hydride. I was impressed by the simplicity of the equipment, as advertised, ‘So simple nothing could go wrong.’ Not quite. The physicist began stacking the uranium cubes as I stood next to him and watched with considerable interest. It was my first experience with a prompt neutron reactor approaching criticality, and I was thrilled in expectation. After a while, as the stack got quite large, I asked why the neutron counter was not counting. I was assured that this was regular and that it would not start counting until we were closer to the critical point. Uncomfortably, I gave the neutron counter a hard going over and asked if the signal light on the high-voltage supply was operative or if it was burned out—as is often the case. The voltage was indeed turned off, so the neutron counter was not working. When the voltage was turned on, the counter to my horror started blazing away. A few more cubes and the stack would have exceeded criticality and could well have become lethal. I was outraged. This incident was my closest brush with death. The reason given was that a wooden table instead of a metal table was being used for the first time, so thermal neutrons were reducing the critical point.”
The plutonium bomb—the one tested at Trinity and dropped over Nagasaki—turned out to be a very different creature from the simple Little Boy. In April 1944, Emilio Segrè determined that the plutonium coming from the Hanford reactors was less pure than the material envisioned in the design calculations, that Hanford’s product would spontaneously fission. This meant that in a bomb, the chain reaction would start before critical mass was reached—what scientists refer to technically as “fizzle.”
An Oppie protégé from Caltech, Seth Neddermeyer, was struck when an army ordnance expert told the scientists they were wrong to use the word explosion to mean detonation; the correct concept was implosion. Seth imagined a ball of plutonium the size of an orange, not critical in that state, compressed to a ball the size of a shooter marble. The pressure would combine with the merger of two plutonium halves to trigger a chain reaction. Oppie, Fermi, and Bethe all argued against Neddermeyer’s proposal, but Johnny von Neumann insisted that, with the right explosive lenses, it would work. Edward Teller: “Just as a beam of light changes its direction when it passes through water and can be focused by passing it through a glass lens, the direction of a shock wave produced by the explosive can be focused and redirected by passing it through different explosive materials. Explosive lenses consist of various pieces of explosives that are fitted together so that the detonation waves move at different speeds as it passes through different portions of explosive.”
Born in Budapest in 1903, Janos von Neumann was so eminently brilliant that fellow Hungarian Quartet member Eugene Wigner remarked, “Only he was fully awake.” In 1928, he published the Theory of Parlor Games, a breakthrough in game theory, and with 1932’s Mathematical Foundations of Quantum Mechanics, he reconciled the competing mathematics of Erwin Schrödinger and Werner Heisenberg. In 1933, he was selected with Albert Einstein and Kurt Gödel for Princeton’s Institute for Advanced Study, where he remained until his death. There, his colleagues complained about his penchant for enjoying extremely loud German marching music on the gramophone, but far more problematic was that he liked to read books while driving cars. His many collisions inspired a Princeton intersection—the “von Neumann corner.” The mathematician was also famously natty. At his 1926 doctoral interview, one of the judges asked, “Pray, what is the candidate’s tailor?” If anyone remembers anything about him at Los Alamos, it was the suit and tie he wore to hike the desert, or the time he rode a Grand Canyon mule in a three-piece pinstripe. Von Neumann threw lavish, outrageous parties; slept a bare four hours a night; and loved to eat and loved to drink. His devoted wife, Klari, said that he could count everything except calories and had “an almost primitive lack of ability to handle his emotions.”
For Neddermeyer’s plutonium-orange-into-shooter-marble notion, von Neumann did shock-wave calculations that proved implosion would work if it did not deviate by more than 5 percent of perfect spherical symmetry. He and explosives e
xpert George Kistiakowsky (known as Kisty) invented a lens implosion system of blocks, in the shape of a pie cut into pieces, the size of car batteries. The fast-burning, wider edge was focused by the slower-burning narrow end of the pie piece so that the detonation waves would arrive together, achieving that perfect sphere.
Just as the mesa was to achieve all of its astonishing goals, personal resentment ushered in sabotage. Hans Bethe:
At the start I had regarded Teller as one of my best friends and as the most valuable member of my division. Our relation cooled when Teller did not contribute much to the work of this division [the theoretical division, which had the main responsibility for the conceptual design of weapons]. More important perhaps for a disturbance of relations was his wish to spend long hours discussing alternative schemes which he had invented for assembling an atomic bomb or to argue about some remote possibilities why our chief design might fail. . . . [Then] he declined to take charge of the group which would perform the detailed calculations of the implosion. Only after two failures to accomplish the expected and necessary work, and only on Teller’s own request, was he, together with his group, relieved of further responsibility for work on the wartime development of the atomic bomb. . . . Since the theoretical division was very shorthanded, it was necessary to bring in new scientists to do the work that Teller declined to do. Partly for this reason, some members of the British Atomic Energy team, already working in the U.S. on other aspects of the Manhattan District project, were brought to Los Alamos and asked to help with this problem. The leader of the British theoretical group was Rudolf Peierls, and another very hardworking member was Klaus Fuchs.
A smidgen of a man in comically oversize eyewear, Klaus Fuchs was perhaps the least physically imposing of any human being on the mesa. He had come to New Mexico as a member of the British Tube Alloys team, all of whom had forgone oversight by American intelligence after Groves was assured that British intelligence had thoroughly security-checked its members. Fuchs would become such a devoted worker that he would rise in the organization until he was a key player on the plutonium-design team, the fundamental group behind the gadget that was Trinity.
A security officer casually mentioned to Klaus Fuchs that army intelligence knew the Soviets had a number of spies working in London and the United States, but that the Anglo-Americans only had one agent in all of Russia. Fuchs thought this was especially funny as he happened to be a spy working for Russia. Laura Fermi: “The first Sunday I was there, a group of friends organized a picnic in a canyon. Our car was needed, but I wouldn’t drive in that unknown, wild territory. So the Peierls asked Fuchs, their friend and protégé, to drive my car. He was an attractive young man, German-born, with a quiet look through round eyeglasses, who answered sparingly to my questions. Even as he spoke to me, he was leading a double life, that of a competent physicist appreciated by his colleagues, and that of spy. As he was to confess in 1950, he was giving secret information to the Russians on the progress of the atomic bomb. Fermi was to say Fuchs had made it possible for the Russians to make an atomic bomb five to ten years earlier than they would have otherwise.”
The great Cold War slander that would tear apart the global physics community and destroy the Los Alamos alumni’s Edenic spirit—that Robert Oppenheimer might not be loyal to the United States, as he was not unswervingly devoted to developing thermonuclear weapons—would be in part advanced by Edward Teller, who could easily be considered treasonous for his own wartime dereliction of duty. Teller’s refusal to do his assigned implosion calculations inserted a Russian agent at the center of Los Alamos, while army intelligence’s and the FBI’s obsession with Oppenheimer’s jejune Communist flirtations left them blind to one of the greatest feats of espionage in modern times.
Klaus Fuchs was originally sent to America as one of fifteen British scientists helping to develop Harold Urey’s gaseous-diffusion technique for producing weapons-grade uranium. Fuchs was already a refugee from the Nazis, as his Soviet handler, Harry Gold, reported: “While Klaus was a mere boy of eighteen, he was head of the student chapter of the Communist Party at the University of Kiel . . . and Klaus, a frail, thin boy, led these boys in deadly street combat against the Nazi storm troopers . . . and later, when the Nazis had put a price on his head, he barely managed to escape with his life to England.” His sister Elizabeth had also been a member of the Communist Party fighting Hitler; as she was about to be arrested, she jumped in front of a train; while Fuchs’s mother committed suicide, grotesquely, by drinking hydrochloric acid.
Klaus Fuchs was, like many other agents operating in post-Depression Britain and America, a true believer in communism as the best system of economics and government, as committed to the cause as Jean Tatlock, the great love of Oppenheimer’s life, who told a friend she couldn’t bear to go on living if she believed Soviet life was inferior. Ethel Rosenberg’s elder brother, Samuel Greenglass, got so tired of hearing about her and Julius’s love of the Soviet system that he “offered to pay the transportation to Russia . . . if they would agree to stay there.” After Ethel’s little brother, David, was drafted into the army as a machinist and assigned to Los Alamos on August 4, 1943, he worked with implosion under demolition expert George Kistiakowsky, machining high-explosive lenses. From basic training, David wrote to his new bride, Ruth, that world socialism was inevitable, even in America, and wasn’t that glorious? When the lonely Ruth then had dinner with her in-laws, Julius Rosenberg explained that David should help Moscow by passing along information, since it was unfair that the United States and United Kingdom weren’t sharing their technology with their Russian allies. When Ruth went to New Mexico for a second honeymoon and relayed the information to her husband, David said that Julius was his hero, and that absolutely he would do it. Another Los Alamos employee, the nineteen-year-old Theodore Hall, agreed with Julius that it was repugnant for America and Britain to keep atomic secrets from the Soviets. While on vacation in New York, Hall figured out how to contact Soviet authorities and became the third enemy agent at the epicenter of nuclear research. His NKVD handler, “Helen,” Lona Cohen, became a legend in NKVD history for her epic sangfroid. One story: Helen was aboard a train and waiting to depart with Hall’s Manhattan Project materials hidden in a Kleenex box. Some undercover FBI agents approached. She began fumbling around with her bags, pretending to look for her ticket. A conductor came over; she handed him the Kleenex box, in the middle of which the Feebs interrogated her. They left, she got her Kleenex box back, and went on to New York.
The Russian search for Anglo-American nuclear secrets began when, after independently discovering spontaneous fission in 1940, Georgi Flerov and Konstantin Petrzhak were nominated for a Stalin Prize, but their work was not validated or cited by scientists in the rest of Europe, so the prize was never awarded. During the mass evacuations before the Wehrmacht invasion, a still-upset Flerov decided to investigate the scientific journals at one abandoned university’s library. Not only was his work not cited, the whole of nuclear physics had vanished from the world’s publications. Flerov suddenly realized what this meant: Britain and the United States were developing nuclear weapons. The lieutenant, all of twenty-eight years old, wrote directly to warn Joseph Stalin.
The NKVD maintained a global network of spies operating out of Soviet embassies, and one field of great expertise was industrial espionage, stealing patents, processes, and formulas so the Russians wouldn’t have to pay licensing fees. American chemist Harry Gold, the Soviet handler for both Fuchs and Greenglass, became an agent for the Soviets in 1935 by providing the formulas for anesthetics and lacquer solvents. During the 1940s, Moscow’s American network was so extensive it seemed to be omnipresent. Kitty Oppenheimer’s first husband, Joe Dallet, was killed while volunteering for the Spanish Civil War; one of his good friends in Spain, Steve Nelson, became an agent in Berkeley, gathering information on Lawrence’s cyclotrons, isotope separation, and other technologies that would become significant in producing nuclear weapons. Ca
nadian Alan Nunn May had been recruited by Donald Maclean in Cambridge; he worked with Tube Alloys; Chicago’s Met Lab; and the heavy-water reactor in Canada’s Chalk River. The Russian network was so good that, when the KGB’s files were opened after the fall of the USSR, it was revealed that the Russians had known quite a bit about Fermi’s first nuclear reactor in Chicago, but they had translated the reactor’s location—squash court—as “pumpkin patch.”
Since 1938, the NKVD—which oversaw the civil police, the secret police, and domestic and foreign espionage, as well as managing the Great Terror—had been run by the brutal, sadistic, and perverted Lavrenti Pavlovich Beria, who was described by a diplomat as “somewhat plump, greenish pale, and with soft damp hands . . . a square-cut mouth and bulging eyes behind his pince-nez . . . a certain self-satisfaction and irony mingled with a clerk’s obsequiousness and solicitude,” and by a Russian as “placed in control for the precise purpose of inspiring deadly fear. I often asked myself—as others assuredly did in their secret hearts—why Stalin had decided to take this step. I could find only one plausible answer. It was that he lacked faith in the patriotism and national honor of the Russian people and was therefore compelled to rely primarily on the whip. Beria was his whip.”
On February 16, 1945, Harry Gold told his superiors that Klaus Fuchs had determined what was needed for the Soviet atomic program to succeed, and by June the diminutive agent submitted “a description of the plutonium bomb, which had been designed and was soon planned to be tested at Alamogordo; a sketch of the bomb and its components with important dimensions indicated; the type of core; a description of the initiator; details as to the tamper”; and “the names of the types of explosives to be used in the bomb [information important to the design of high-explosive lenses]; the fact that the Trinity test explosion was to be made, with the approximate site indicated, soon, in July, 1945, and that this test was expected to establish that the atom bomb would produce an explosion vastly greater than TNT and the comparative estimated force of this explosion was indicated in detail with relation to TNT.” On Sunday morning, June 3, 1945, Gold went to the Greenglasses to pick up sketches of Kisty’s various implosive lenses, including schematic views of their layers and detonators. It was the first meeting between agent and handler, one that Gold remembered well: “Greenglass was not only young, but at once impressed me as being frighteningly naive, particularly in his eager volunteering of the idea of approaching other people at Los Alamos as potential sources of data. I was horrified at his total inexperience in espionage, especially considering what we were after.”