The engineers at Kellex had developed a preliminary design of the diffusion plan, ordered components, and begun the site preparation for construction in Oak Ridge, Tennessee. With the British team’s more sophisticated design too late to be useful, its role became one of calculating how the plant’s thousands of components and stages would respond to small changes. Fuchs took up the task, and January 5, 1944, saw his first report, MSN-1 “Stability of Plant with Reset Controls.” More followed quickly.
* * *
—
Between his arrival and the first report, Fuchs went to his sister Kristel’s house in Cambridge, Massachusetts, for Christmas. It had been seven years since they had seen each other in Bristol, and her life had changed dramatically. She was now married with two children and chose to be called Christel, the baptismal spelling of her name.
While at Swarthmore, she had a scholarship covering the tuition, as well as free room and board with a wealthy, somewhat demanding woman who lived on the Main Line. She went to classes, struggled to learn English and adjust to a new educational system and culture, and worked afternoons in a tearoom.
In 1938, her student visa was to expire, and replacing it with a permanent one required applying while outside the United States. The U.S. embassy in Cuba had a reputation for expediting the process, although it wasn’t guaranteed. She was afraid of arriving there, being denied a visa, then facing a one-way trip back to Germany.
But she made the trip and returned to Swarthmore by the first week in June without incident and, with the new visa, as a happy young lady. And a fortunate one. An intensive refugee crisis in the United States began that June. The 1924 Immigration Act allowed a total of 150,000 visas per annum apportioned among countries: the count for Germany was 27,370. In November 1938, after Kristallnacht, when Nazis burned down synagogues and assaulted Jews, a Gallup poll asked Americans if the United States should take in more Jewish exiles. A resounding 72 percent said no. In 1939, the waiting list was about 310,000. The allotted number of visas didn’t change.
Christel never received her degree. In October 1938, she married Bob Heinemann, who had graduated from Swarthmore in the spring and enrolled as a graduate student at Harvard. From Cambridge, she worked tirelessly, and futilely, to bring Gerhard and Elisabeth along with Elisabeth’s son and husband to the United States.
* * *
—
On February 5, 1944, a wintry Saturday afternoon in Manhattan, Klaus made another journey, one that would change the course of his life and, some might say, the course of history. As darkness fell, he reached the appointed place on Henry Street set up before he’d left Birmingham. This was the Sabbath, in the heart of a Jewish neighborhood on the Lower East Side, and the sidewalks were deserted.
But then, across from a fenced excavation site, he saw a short, full-faced man wearing a dark suit and an overcoat. He wore gloves as well, but he carried an additional pair.
Dressed in tweeds, Klaus carried a book and a green tennis ball. He crossed the street, and the man asked him, “What is the way to China town?” He had a strong Philadelphia accent.
Klaus responded, “I think China town closes at 5 o’clock.”
This, their first encounter, went exactly as planned, except that the man from Philadelphia was to carry a single glove, not a pair. And Klaus wanted to be called by his name and drop his code name, Rest. The other man went by “Raymond.”
Slowly, they turned and walked together down the street. Sensing Klaus’s reserve, Raymond chatted about himself until Klaus seemed to relax. They took the subway and then a taxi uptown and ended up at a restaurant on Third Avenue. The conversation over dinner was sparse. Klaus was still uneasy, and he didn’t consider a restaurant a safe meeting spot. He could have been followed from work.
After dinner, they strolled, and Klaus explained his assignment on isotope separation. Besides the work in Manhattan, research was taking place in Berkeley, California, and at a place simply referred to as Camp Y, possibly in New Mexico. Researchers in England were carrying out preparatory work, and the United States was in charge of production. The work in the United States was done in “water-tight compartments” for security so that no one knew the full scope of the project. Klaus told Raymond that results were expected in 1945, but he was doubtful.
Before going their separate ways, the two men agreed to rules for future meetings: no restaurants, no place twice, as brief as possible. The overriding rule was caution. Accordingly, for this first meeting, Klaus had brought no materials. But both understood that in the future he would furnish Raymond with everything he could.
Prior to this rendezvous, Raymond had been told almost nothing about Rest (name used in Russian messages), except that he was a scientist. He began his report with the basics: “He is a member of a British mission to the U.S. working under the direct control of the U.S. Army. . . . The work resolves itself mainly into a separation of the isotopes . . . with the diffusion method. . . . He is most likely a very brilliant man to have such a position at his age (he looks about 30).” Raymond reassured his superiors: “He obviously has worked with our people before and he is fully aware of what he is doing. Also, he is apparently one of us in spirit.” Raymond’s estimate shaved Klaus’s age by a couple of years.
Raymond handed off his report to “John,” an operative at the Russian consulate in New York. Its next stop would be the KGB’s Moscow Center.
The KGB knew a lot about Klaus. Staff in Moscow had received a lengthy brief from the GRU on its history with Klaus in London, attesting to his credentials and values: Klaus believed in communism, his motives were ideological, and he worked on war research. On handing him over to the KGB, the GRU advised that he took no pay but sometimes accepted monetary gifts.
The memo from the KGB’s Moscow Center to its staff at the consulate in New York exuded excitement. Pressures on them had mounted owing to their failure to infiltrate U.S. war research. Now they had something. The memo proclaimed, “As an agent, ‘Rest’ is a major figure with considerable opportunities and experience in agent work.”
But there were also reservations. “Be very cautious when working with Rest,” Moscow Center advised. The threat of U.S. counterintelligence was ever present. Surprisingly, there was another potential hazard—the GRU itself. In the opinion of the KGB, its spying partner, which had handed over Rest, was “not known for its discretion.”
For the next several months, meeting once a month—sometimes more—and always at night, Klaus and Raymond hopscotched from the Queensboro Bridge to Greenwich Village, to the Grand Concourse in the Bronx, to Queens Boulevard in Long Island City. Along jammed streets, in dark alleys, and in dimly lit cafés, they had fleeting encounters where Klaus handed over handwritten documents. He knew that the copies typed at work were numbered and couldn’t be used because each one was distributed to a specific person. But the typists gave the original, longhand drafts back to him, and these he handed to Raymond. Anything else of importance he put in writing. He could tell that Raymond had some scientific background, but he didn’t think he would grasp the complexities of the research.
Raymond had his own drill. Within half an hour of the rendezvous, he met his controller on a nearby street corner and transferred the folder. Once, his curiosity gnawing, he opened the folder. He saw page upon page of mathematical equations.
One day, Klaus asked about the reaction to his material. Raymond said it was “completely satisfactory” but that Moscow Center wanted more: a detailed description of the “whole set-up”—that is, production plans and drawings. Obviously aggravated, Klaus replied that he had handed that over in England. His research in America was different, and it would be dangerous for him to carry that kind of material. But finally, he agreed.
Raymond was pleased with the material he was able to supply to Moscow Center, but unexpectedly, they chastised him. Why had he, “Goose”—his code name in the messages to his
superiors—not provided “precise” information on Rest himself: place of employment, address, meeting arrangements, his impression of Rest. And they admonished him about the lack of a backup if contact were lost.
Early on, the two men had fabricated a detailed cover story for their friendship—a symphony concert at Carnegie Hall where they had sat next to each other, chatted, and become friends. With this prop they sometimes relaxed their taboo on dining to enjoy a rapport filled with office news.
One night, Klaus described his supervisor’s visit to Camp Y to consult on developing a large-scale “launch” of a bomb. Another time, he told Raymond about a “definite break” between the British and the Americans. The British wanted to build their own diffusion plant in England to separate isotopes, a direct breach of an agreement.
The work of the British team in New York was self-limiting and, by May, coming to an end. This led Klaus to warn Raymond that his next assignment—England or Camp Y in New Mexico—was uncertain. He might be leaving for England in six weeks.
Peierls had already left for Camp Y, a.k.a. Los Alamos, New Mexico, and the site of the construction of the atomic bomb. The Theoretical Division needed mathematical physicists to accelerate the delivery of a plutonium bomb.
* * *
—
The scientists and engineers at Los Alamos had developed a bomb using the fissile material U-235 with a simple gun-type device, where a projectile of a subcritical mass of fissile material meets another subcritical mass to create a critical mass and start a chain reaction. But enriching uranium with U-235 was a lengthy process. An alternate fuel existed: plutonium, an element that could also sustain a chain reaction. Researchers had determined that sufficient quantities of plutonium were quicker and easier to obtain. Trace quantities appear in U-238, and a few years before, scientists had discovered that they could produce more through neutron capture by U-238, which would subsequently decay to plutonium’s fissile isotope PU-239.
It wasn’t to be an easy solution, though. In April, they realized that their simple, gun-type device worked well for a U-235 bomb but wasn’t suitable for plutonium. Because plutonium’s rate of spontaneous fission was too fast, plutonium fuel in a gun-type bomb would fission before reaching a critical mass and create an abbreviated explosion, that is, a “fizzle.” A plutonium bomb required a completely new—and unexplored—approach.
A weighty question confronted Robert Oppenheimer. Should he make an abrupt shift from a dependable gun-type bomb with a limited fuel supply to one clouded by uncertainties but with more readily available fuel? The outcome of the project—and perhaps of the war—could depend on that decision. Oppenheimer anxiously mulled it over for a few months. With input from Peierls and others, he became convinced that they must start over and design a plutonium bomb.
A far lesser, but still important, uncertainty was the placement of Fuchs and Skyrme. Tube Alloys administrators in London and Peierls in Los Alamos debated whether they were to go home to design a now viable gaseous diffusion plant or go out west to Camp Y to design a bomb. Peierls had requested that both of them go west.
As officials pondered Fuchs’s fate in the first weeks of June, Allied troops landed on and secured the beaches of Normandy. Victory over the Germans now seemed within reach—unless, of course, the Germans had an atomic bomb being readied to drop on England.
The decision to transfer Skyrme to New Mexico came quickly, but Fuchs’s deployment remained a subject of debate. Kearton wanted Fuchs back in the U.K. to push forward the work on diffusion. Peierls could go along if the diffusion work was really a serious effort, but he and Hans Bethe, the head of the theoretical physics division at Camp Y, doubted that it was, and thought that Fuchs would be more valuable at Camp Y. Bethe was an esteemed physicist and later Nobel laureate, a German refugee who knew the British team well. His journey to America wove through England: first Cambridge, then Manchester, where he had lived with the Peierlses, and finally Bristol, where he first met Fuchs. Bethe had overlapped with Gerhard Fuchs too at the Odenwaldschule.
A month into the deliberations, those in charge tilted cautiously in favor of bringing Fuchs back to England. But Kearton hesitated, fearing that the Americans would interpret Fuchs’s transfer home as a slight, a lack of commitment to the war effort. Fuchs, too, favored returning. Without identifying the location of Camp Y, Peierls had told him its purpose. Fuchs felt he could make a “special contribution” in the U.K. At Camp Y, he saw himself as one of many and not able to make a significant difference. He stated his preference, but he didn’t argue it.
The dithering left Fuchs restless and bored, living alone in an apartment on the West Side and rarely socializing. He did receive one dinner invitation, though, from Maria Goeppert Mayer, a scientist on the Manhattan Project team at Columbia University and a future Nobelist. She was an old friend of the physicist Edward Teller, who met Fuchs while en route to Los Alamos in early 1944. Teller wrote to Maria that Fuchs was a very nice man and someone she would find interesting:
He was a student of Born and you remember that he has worked on Joe’s [Maria’s husband] theory of condensation. . . . In talking, his spontaneous emission is very low but his induced emission is quite satisfactory.
* * *
—
In mid-June, Fuchs sent Peierls his latest report, MSN-12 “Fluctuations and the Efficiency of a Diffusion Plant—Part III,” which outlined a theory with “just tolerable” conditions for bypasses in the diffusion process. After he finished a couple of other reports, he complained to Peierls that being “practically out of work, I have tried to comfort myself by considering what we have done during the last months.” That resulted in a dense, single-spaced four-page report in which Fuchs succinctly summarized their work:
In the diffusion plant for the production of the isotope uranium 235, the [gas] uranium hexafluoride passes through several thousand states which are all interdependent on each other. Conventional measures of pressure and flow control are completely inadequate to control such a complicated system, and I developed the theory of the control system of such a plant, which was further amplified by the research group at Kellex and applied to the operation of the diffusion plant. Also, I developed the theory of the effect of the remaining pressure and flow fluctuations on the performance of the diffusion plant and advised Kellex on steps that could be taken to minimize losses of performance.
Out of the British mission’s seventeen reports, Fuchs wrote ten, the remainder from Peierls and Skyrme. The Americans had much to thank the British team for, especially Fuchs.
* * *
—
At the end of July 1944, Klaus made two more trips. The first was to Washington, D.C., to see the director of the British mission and resolve the issue of where he would work next. When he left, the decision was for him to go to London.
He then traveled to Massachusetts to say goodbye to Christel, leaving her with instructions in case Raymond (whom he referred to by another name) visited her. Fuchs was vague about where he was going.
As Oppenheimer moved decisively to support plutonium and the design of a new triggering device, Fuchs’s instructions changed: he was now going to be deployed to Los Alamos.
* * *
—
When Fuchs’s British employer, the Department of Scientific and Industrial Research, initially proposed to send him to America in 1943, MI5 had queried whether his appointment was short-term or permanent. DSIR answered that it was the former. Once he was in the United States, Peierls quickly requested an extension, and DSIR forwarded it to MI5, which reconsidered Fuchs’s security clearance. It returned a qualified endorsement for Fuchs to stay: DSIR should not mention Fuchs’s “proclivities” to officials there.
No one revisited this topic with regard to Camp Y. Neither Peierls nor Bethe was aware of the questions about Fuchs’s loyalties.
* * *
—
On August 5, Klaus and Raymond were to meet in Brooklyn in front of the Bell Cinema, near the Brooklyn Museum of Art. Raymond stood around and waited. No Klaus. They always set a backup date, but Raymond had to be someplace else. He did show up for the next date, but he stood there alone. In short order, Moscow Center’s fear had come true.
Unknown to Raymond, Fuchs was on his way to Camp Y. On the eleventh, he took the train to Chicago and then boarded another to New Mexico.
Raymond plotted with his controller to figure out how to recover what was one of the KGB’s most valuable assets—if not the most valuable. The plan they came up with—sending Raymond to Klaus’s apartment—violated all the rules, but this was no time for scruples. John found Klaus’s address, and Raymond bought a book to use as a guise for his visit. He inscribed Klaus’s real name and address in it and set out for 128 West Seventy-seventh Street.
West Seventy-seventh was a quiet, narrow street lined with trees and brownstones. Raymond easily gained entry to number 128. As he searched for Klaus’s apartment along a corridor, an old woman stuck her head out from her apartment. He queried her, and then the janitor who happened by, as to the whereabouts of his friend. Raymond wanted to return a book, he explained. From them, he learned that Klaus had left . . . to go “somewhere on a boat.” Not good news.
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