Gold went out to New Mexico in mid-September. The trip had been difficult to organize; he had trouble getting time off from work and he was short of money. From the Palmer House in Chicago, where he spent the night of September 16, he called his old friend Tom Black in Newark and asked Black to wire fifty dollars to him care of the Albuquerque Hilton. Black was able to raise only twenty dollars but loyally sent it on.
With Curtis LeMay in the air in his B-29 somewhere eastward of Hokkaido, Gold arrived in Albuquerque on Wednesday, September 19, 1945, and signed in at the Hilton. He was scheduled to meet Fuchs that day on the outskirts of Santa Fe, at a time Gold remembered as “very late in the afternoon, about six o'clock.” Once again he caught a bus up from Albuquerque. Fuchs arrived at the rendezvous in his dilapidated Buick uncharacteristically late — “fully twenty or twenty-five minutes tardy,” says Gold, who always felt exposed when he was waiting for a contact — and they drove off into the Santa Fe hills. Fuchs told the portly chemist apologetically that he'd had difficulty getting away. As Gold remembered it, the physicist and his “friends with whom he worked at Los Alamos” were having a party “that very evening… to celebrate the successful use of atomic energy in the form of a weapon”; Fuchs was hauling a supply of liquor. The occasion must have been the formal British Mission party held at Los Alamos not that evening but three days later on Saturday, September 22, “in celebration of the Birth of the Atomic Era,” as the formal invitations proclaimed. The party featured a footman announcing guests, steak-and-kidney pie served on paper plates, several hundred paper cartons of trifle, a full-scale pantomime, dancing and many toasts — enough work to keep the British staff on the Hill busy throughout the week making preparations. Fuchs evidently contrived to get away to his rendezvous with Gold by volunteering to pick up the liquor. Gold could not have learned about the British Mission party from a source outside Los Alamos. That he approximately recalled Fuchs's late- September circumstances five years later is significant confirmation of his veracity.
Fuchs had only just finished writing the report he was delivering to Gold. “En route… for this planned meeting…,” he would confess, “I stopped somewhere on the way in the desert, drove off the highway to a solitary place, and wrote a part of the… paper… which I planned to deliver… ”
Driving, Fuchs had much to say. He had attended the Trinity test, he told Gold, and learned later that the flash of the explosion had been visible all the way up at Los Alamos, two hundred miles northwest, despite overcast skies and rain. “He himself was rather awestricken by what had occurred,” Gold paraphrases Fuchs. “… Frankly, he had not been too certain that the project might not have been abandoned before it was completed, and… certainly he had grievously underestimated the industrial potential of the United States… He was also greatly concerned by the terrible destruction which the weapon had wrought.” Fuchs was not the only one at Los Alamos disturbed by the death tolls at Hiroshima and Nagasaki. His great concern was evidently not sufficient to lead him to reconsider proliferating the destructive new technology to the Soviet Union.
At some point Fuchs pulled off the road and parked — “a fair distance away” from town, says Gold, “because below us I could barely see the lights of Santa Fe in the distance.” The physicist continued his recitation of marvels. “He told me that whereas, before, the townspeople in Santa Fe had regarded them, the people of Los Alamos, as a sort of ‘boondoggling’ outfit engaged in work which they could not comprehend, that now they were
hailed on all sides as conquering heroes… “A Los Alamos security officer,
Fuchs said, told him casually one day that Army intelligence realized there were “hundreds” of Soviet agents in the US and England, but the British and the Americans together had “only one” agent in the Soviet Union. Fuchs laughed at the discrepancy, Gold remembered.
From derisive, Fuchs turned somber. He had been barred from some sections of the project, he reported; “the relationship between the British Mission and the United States, which once had been extremely cordial and free, had now become somewhat strained, and… there was no longer the free exchange of information between the two groups.” He expected to be returning to England before the end of the year or early in 1946, “where he would again resume work on atomic energy, exclusively for [the British].” British intelligence had notified him that they were trying to contact his father and might bring Emil Fuchs to England. Fuchs was “very much concerned” about his father's “welfare and health,” but he was also worried that his father would talk too much: “Klaus told me that as far as he knew the British had no inkling about his past as it related to his Communist activities, and he was anxious that this continue so.” Gold told him “to proceed as he thought best”; possibly, Gold consoled him, “he was greatly overestimating the extent to which the old man would talk and also the extent to which the British might be interested in Klaus’ past.” As it turned out, Gold was right on both counts.
Yatzkov, with his high-level informants in Washington, had heard that Fuchs would soon be returning to England and had prepared Gold with a London contact protocol, which Gold now passed along to Fuchs. Fuchs mentioned that he might stop off to visit his sister in Cambridge again around Christmastime “and that the best way of ascertaining his whereabouts was to make an inquiry shortly before that time.” Fuchs drove Gold back to Santa Fe. “The last event that transpired before Klaus dropped me off… was that [he] gave me the packet of information relating to atomic energy.” Fuchs drove away; Gold headed for the bus station. “After a period of anxious waiting, about an hour and a half, I finally obtained a bus going back to Albuquerque.”
American Airlines woke Gold at the Albuquerque Hilton at two-thirty Thursday morning to confirm a seat as far as Kansas City. From Missouri Gold took the day coach to Chicago, caught a train late that night to New York and from New York, still carrying Fuchs's packet, commuted home to Philadelphia. He returned to New York the next day, September 22, to meet Yatzkov and transfer Fuchs's packet, but Yatzkov, alerted by now to the Canadian espionage debacle, failed to appear. At a backup meeting in Queens early in October, Yatzkov finally took the incriminating documents off Gold's hands. He met regularly with Gold throughout the rest of the year, but by December Gold noticed that he was “very touchy and very apprehensive.” Yatzkov told him “they had to be extremely careful.” Gold got the impression Yatzkov “had the wind up.”
Fuchs's report added additional details to the full description of the Trinity plutonium implosion design that he had passed Gold in June. He noted that the production rate of U235 was up to a hundred kilograms per month and of plutonium to twenty kilograms per month and gave the critical mass of each material so that the Soviets could calculate roughly how many bombs the US was capable of stockpiling. He communicated important information about plutonium phases — different crystalline states, each with unique properties.
Plutonium is a bizarre metal. Determining its metallurgical properties had given Los Alamos metallurgists much trouble. “Plutonium is so unusual,” its discoverer, Glenn Seaborg, once told a reporter, “as to approach the unbelievable. Under some conditions, plutonium can be nearly as hard and brittle as glass; under others, as soft and plastic as lead. It will burn and crumble quickly to powder when heated in air, or slowly disintegrate when kept at room temperature. It undergoes no less than five phase transitions between room temperature and its melting point. Strangely enough, in two of its phases, plutonium actually
Fuchs reported the results of the Trinity test, described his work on initiators and explained how the Fat Man design had been preassembled with one HE lens left out and a removable plug drilled through the tamper to form a passageway to the center of the assembly through which the core could be inserted. He reported that the uranium-separation filters (“barriers”) developed for the Oak Ridge gaseous-diffusion plant were made of sintered nickel, a material that had only been identified after a long and difficult search. On this occasion and later, he passed along information about composite core design, emphasizing the economic advantage to the United States of drawing on both isotope separation and plutonium production for bomb materials. He knew about levitation as well and probably reported it. Once again David Greenglass's ad hoc information would usefully corroborate Fuchs's scientifically accurate account; in this instance Greenglass had even reported the new developments first.
The head of Soviet foreign intelligence, Vsevolod Merkulov, sent Lavrenti Beria a detailed plan of the Fat Man plutonium implosion bomb on October 18, 1945. The top secret seven-page document began with a summary:
GENERAL DESCRIPTION OF THE ATOMIC BOMB
The atomic bomb is a pear-shaped projectile with maximal diameter of 127 cm and 325 cm long, fins included. The total weight is around 45,000 kg. The bomb consists of the following parts:
