Shall I just call up Mr. Roosevelt and ask him to save us all from a fate worse than death?
—WR, from “The Uranium Bomb”
DURING the long, frustrating spring of 1941, weeks that had been marked by heightening political tension, Loomis’ involvement with the Rad Lab became increasingly sporadic as he found himself pressed into service on another scientific front. A number of leading physicists had become alarmed by the snail pace set by Lyman Briggs, the chairman of the uranium committee, to say nothing of the extreme difficulty in obtaining the materials and funds necessary for their experiments, and had brought their concerns to Loomis. The potential of the discoveries in nuclear fission had major implications, and scientists in both England and America were whispering about the possibility of constructing a bomb of enormous power. At this point, no one could reasonably doubt that America’s involvement in the European war would increase, yet no one on the uranium committee could be persuaded that fission was critical to the war effort.
Worried that the Germans might already be ahead of them, they turned to Loomis, who had been instrumental in jump-starting the radar lab and was widely liked and respected, and begged him to use his influence to spur the government into action. Loomis disliked being drawn into these political squabbles, which he generally viewed as beneath him, but owing to his friendship with Lawrence, and pride in the achievements of the Rad Lab, which he justly felt would always extend to him, too, he began working behind the scenes to solve the uranium problem and push the government to get on with building the bomb.
In spite of the many obstacles, a year or more of research had yielded some important findings at various laboratories across the country, and Loomis shared his colleagues’ doubts as to the Briggs committee’s ability to appreciate the full weight of their implications. At Columbia, Fermi, working with Szilard, had gained a reasonably good understanding of the chain reaction in a uranium-graphite system, and Loomis knew they were in desperate need of more graphite to proceed with the next phase of their work. At the University of Chicago, Karl Compton’s brother, Arthur, a Nobel Prize–winning physicist, was investigating beryllium as a moderator that could contribute to a successful chain reaction. Harold Urey, another Nobel laureate and the discoverer of heavy hydrogen, had done some promising studies showing it might be possible to obtain a chain reaction using heavy water. At the University of Virginia, Jesse Beams was working on isotope separation to achieve uranium 235, while at Harvard, George Kistiakowsky, who had worked for Loomis at Tower House and was now head of the university’s Chemistry Department, was checking out gaseous diffusion as another possible means of separating uranium isotopes.
Meanwhile Lawrence, the great force in marshaling American physics, had become persuaded of the importance of nuclear weapons and was lending his voice to the growing discontent. Always on the lookout for ways to further expand his Berkeley operation, he was convinced that the Rad Lab should undertake uranium research, which was clearly receiving scant attention from the government. After all, his cyclotron had produced one of the major breakthroughs in the field. Back in the first flush of excitement surrounding the news of uranium fission, one of his boys—Ed McMillan—had devised an experiment to measure the energies of the fission fragments and in the process detected a mysterious new product of fission—a radioactive substance with a half-life of 2.3 days—which he speculated might be the isotope of the element 93. In subsequent experiments in the spring of 1940, he and another Rad Lab physicist, Philip Abelson, confirmed that it was the new element 93, derived by the capture of a neutron by uranium 238 and prompt subsequent decay.1
This discovery led McMillan to speculate that the element 93—which he suggested be named “neptunium” after the planet beyond Uranus, for which element 92 had been named—might decay to form an isotope of the element 94 with a mass of 239. After McMillan was drafted for radar work at MIT, and Abelson departed for Tuve’s laboratory in Washington, their research was taken up by the Berkeley chemist Glenn Seaborg, who, aided by a young instructor, Joseph Kennedy, and a graduate student named Arthur Wahl, bombarded uranium with deuterons (the nuclei of heavy hydrogen atoms) and obtained a mixture of several isotopes of 93, including evidence of the element 94. Lawrence immediately suspected that 94 might prove fissionable—that it might have nuclear properties. If this was true, it could perhaps replace uranium 235 as a nuclear fuel or explosive.
In mid-December 1940, Lawrence, who was in New York staying with Loomis, met with Fermi at the office of Columbia University physicist George Pegram to discuss the feasibility of making enough of the new substance to do further research, which they all agreed was of the utmost importance. At this point, it was still all speculation. No convincing case could be made to the government without experimental proof of 94’s fission characteristics. If the nuclear properties of the new isotope turned out to be unfavorable, the whole approach could come to nothing. During the meeting, Emilio Segrè, an Italian physicist who had worked with Fermi in Rome and was now a research assistant at Berkeley, suggested to Lawrence that they use one of his cyclotrons to manufacture enough 94 to measure its nuclear properties. “The only way of answering these momentous questions was by direct experimentation,” Segrè wrote in his memoirs. “It was imperative to try.”
After conferring with Loomis and Compton, and consulting Bush in Washington, Lawrence gave his assent. But he was already saddled with radar work and too weighed down by myriad projects and a heavy travel schedule to take on the uranium study himself. He had also been suffering from another of his debilitating bouts of flu and had spent that Christmas convalescing in Florida. As it was, Loomis was so concerned about his hard-driving friend’s stamina that he proposed Berkeley establish a special fund to facilitate Lawrence’s work for national defense. Loomis felt Lawrence was much too valuable to the country to risk his health and personally contributed $30,000 to the fund.
In the end, Lawrence decided to entrust the all-important experiments to Segrè, who would work on the slow neutron fission of elements 93 and 94 with Seaborg’s crew. By this time, the British physicists at the Cavendish Laboratory in Cambridge were becoming interested in 94 and wrote to Lawrence urging him to undertake personally the uranium research. Events overtook the letter. Using Lawrence’s sixty-inch cyclotron, Segrè and Seaborg’s team of chemists had set to work immediately on bombarding uranium—this time with neutrons—and on the night of February 23, they succeeded in identifying and producing samples of an isotope of the element 94. It had a mass of 239, just as McMillan and Abelson had predicted. It would prove to be the fissionable isotope Pu-239—plutonium.
Realizing that the discovery of this new element and its transformation was of immense importance, Segrè informed Lawrence at once but was not sure from his initial reaction to what extent Lawrence grasped the full ramifications of their findings. “He told me to talk to his friend Alfred Loomis, a multimillionaire banker and amateur physicist of great intelligence who was visiting the Rad Lab,” Segrè recalled. “I hesitated because of security, but Lawrence reassured me that Loomis was cleared for every technical secret concerning defense, and that furthermore he was a cousin and close friend of Secretary of War Henry Stimson’s.” Segrè reluctantly sought out the civilian banker, and this time he got the reaction he had hoped for. “Loomis understood everything I told him promptly and completely. I believe he helped to open Lawrence’s eyes, although it is possible that Lawrence had fully grasped what I told him, and simply wanted Loomis to hear the news directly from the horse’s mouth.”
Lawrence, who was shrewder than Segrè gave him credit for, recognized that his cyclotron opened up a whole new way of tapping nuclear energy and had been planning to enlist Loomis’ help in funding his plutonium research. He had sent Segrè ahead only to pique Loomis’ interest, knowing his friend would take a keen interest in the project and would be a powerful ally in pressing for a full-scale program. When Conant, Bush’s deputy at the NDRC, came to Berkeley in early March 1941, Lawrence also went to work on him, urging him to “light a fire” under the Briggs committee. “What if German scientists succeed in making a nuclear bomb before we even investigate possibilities?” he demanded, asking the question he would repeat many times in the weeks to come. Lawrence had been particularly dismayed by Briggs’ reaction to their work and felt his only real concern was with security. Briggs had actually requested Lawrence “guarantee Segrè’s reliability” and had scolded him that Fermi had “only partial clearance.”
ON a bitter cold New England morning on March 17, 1941, Lawrence and Loomis met with Compton at his office at MIT. Lawrence informed Compton that on his own initiative he had been pursuing fission experiments, and although it was not technically his NDRC assignment, he wanted to continue. He was sure that his results merited further investigation, he told them excitedly, and it had occurred to him that he could convert his thirty-seven-inch cyclotron into a huge mass spectrometer. Smaller instruments had already been used to determine the mass and identity of isotopes. It would require only minor modifications, and then it would be possible to use the mass spectrometer to separate uranium 235 from ordinary uranium, thereby isolating the fissionable isotopes. Lawrence, who could not keep from leaping ahead, already envisioned a way the magnetic separation of isotopes could be expanded to become a large-scale process for producing uranium 235.
Loomis and Compton needed no persuading and agreed to back Lawrence’s plan. That afternoon, Compton called Bush and recommended Lawrence be allowed to spearhead a new fission program and cited the widespread dissatisfaction with the committee’s delays and inaction. In a follow-up letter, he summarized Lawrence’s harsh assessment of the existing fission program under Briggs, who was “by nature slow, conservative, and methodical,” and suggested that perhaps the committee had accomplished so little because it “practically never meets.” This was particularly “disquieting,” he added, as “our English friends are apparently farther ahead than we are, despite the fact that we have the most in number and the best in quality of the nuclear physicists of the world.” Compton further recommended Bush appoint Lawrence his deputy for ten days or so—just long enough to launch the program, using the same strategy that had served the radar program so well. Compton’s tone was pointed: given the current crisis, they should be exploring all routes to the bomb, and the NDRC should not “passively administer” the uranium committee but “had a responsibility for insuring . . . that the project goes ahead not only safely but with the greatest expedition.”
The truth was, Bush had his hands full and was charged with too many heavy responsibilities to adequately oversee the Briggs committee. But he did not appreciate being sandbagged by his own trusted lieutenants. He was not sure what irritated him more, that Lawrence had gone off on his own and come up with a method of separating the isotopes of uranium by what amounted to a mass spectroscopy stunt, or that once again he was being presented with an elaborate set of demands by Lawrence and Loomis, who as titans in the worlds of physics and finance had become a formidable duo. “Alfred and Ernest were great friends during the war and at times it got to be embarrassing,” Bush recalled later, referring to their penchant for taking matters into their own hands. “Ernest had no sense of organization and he didn’t have the slightest hesitancy in galloping right around me and going after the Secretary of War, the Congress or somebody. I don’t think he ever tackled the President without my knowing it, but he would have been perfectly capable of doing it.”
Of course, Bush often resorted to the very same tactics and frequently enlisted Loomis’ aid in appealing directly to Stimson. The largest thorn in Bush’s side was the difficulty in establishing and maintaining communication between the army and the scientists, and Loomis became a valuable go-between. Loomis was the only civilian to sit with a group of generals on an army planning board set up by the secretary of war to advise him on the V-1 and V-2 rockets being developed by the Germans. As Stimson noted in his diary, Loomis “looks very seriously on the rocket as a permanent change in military weapons, as important as the first use of the barrel for gun powder.” It would be a result of that board’s decision to take full advantage of all the modern techniques of warfare—including the SCR-584 developed in Loomis’ laboratory, the proximity fuse being developed by Merle Tuve and his team, Bell Lab’s latest advanced computer, and the army’s antiaircraft guns—that the threat from the V-1s was substantially reduced. “Remember, Alfred had a very close personal relationship to Stimson, and that closeness was widely known, and it was something that Bush very much made use of,” explained Caryl Haskins, who worked for Bush. Loomis’ suite at the Wardman-Park Hotel in Washington, which he maintained throughout the war, served as a regular meeting place and was used by Lawrence, Fermi, Bowles, and other scientists when they needed to be available to talk to Bush or Stimson on very short notice. “Alfred spent a great deal of time in Washington administering the radar lab, and he was a force there,” said Haskins. “He picked out some extraordinary people, like Kistiakowsky, and was of help on every technical issue, so that Van relied on him to a great degree.”
Perhaps for this reason, Lawrence’s back-channel lobbying of Loomis—along with Compton and Conant—particularly infuriated Bush, and he perceived it as a blatant attempt to undermine his authority. Lawrence had “decided that when he did not get directly out of me the reaction he wished, he would go around and bring pressure, which he certainly did,” Bush fumed. When they met face-to-face on March 19, 1941, he let Lawrence have an earful: “I told him flatly that I was running the show, that we had established a procedure for handling it, that he could either conform to that as a member of the NDRC and put in his kicks through the internal mechanism, or he could be utterly on the outside and act as an individual in any way that he saw fit.”
After the blowup, Bush moved swiftly to remedy the situation. Realizing Compton’s advice made sense, Bush reluctantly named Lawrence Briggs “temporary personal consultant” and made funds available for further work on the elements 93 and 94. “I made such a nuisance of myself generally,” wrote Lawrence, “that Bush requested the president of the National Academy [Frank Jewett] to appoint a committee to survey the uranium problem and make recommendations.” Once Bush had deflected the political heat by appointing an independent review board, thus delegating the uranium problem to the country’s top theoretical physicists and engineers, he and Lawrence patched up their differences. “I have not been at all disturbed in my own mind about the recent shindig,” Bush wrote him. “There is no personality in the group that is not utterly reasonable when it comes down to brass tacks.”
There remained the problem of deciding fission’s future given the absence, as Bush saw it, of any “clear-cut path to defense results of great importance.” Unfortunately, the review committee’s first report, completed in mid-May, was not optimistic. They could not determine definitely whether an atomic bomb could be made. Arthur Compton, the committee chairman, concluded that “not a single member of the Briggs Committee really believed that uranium fission would become of critical importance in the war then in progress.” There were still too many major scientific problems to be solved and too much confusion about how to approach fission. With no military application yet in sight, some committee members thought the entire uranium project should be shelved until peacetime, when it ultimately might prove a source of power.
In May, Loomis, accompanied by his wife, Ellen, went to Berkeley to collect an honorary degree from the University of California for his work in physics and for “devoting himself single-mindedly to the defense of our country in a time of emergency.” Instead of celebrating, he and Lawrence spent nearly all their time plotting what steps they should take next to spark-plug Compton’s committee, of which Lawrence was a member. In the few hasty letters they exchanged that summer, they continued to keep each other informed of any progress in what they referred to as “the U matter.”
For much of the summer of 1941, Loomis was busy with radar work, and Lawrence was distracted by other demands on his time. The NDRC had asked him to go to San Diego to help stimulate the anti-submarine program, as the Germans were threatening to destroy the convoy system and Britain was on the brink of collapse. Months of relentless U-boat attacks had claimed 328 merchant ships, sinking tons of desperately needed supplies—wheat, beef, butter, explosives, and oil, as well as military equipment. Once again, Lawrence acted as the chief recruiting agent for the new underwater sound laboratories and rounded up former protégés from around the country. He even summoned McMillan from the radar lab to help him out, much to Loomis’ dismay. As Lawrence wrote in a July 10 letter to Bush: “Alfred and Karl, I’m afraid, have a little feeling I’m walking out on them in being so concerned with the submarine program . . . [it] seems so clear the microwave committee is well along . . . on the other hand the submarine program has not gelled and there is urgent need for the best scientific talent.”
But by fall, Lawrence was back at Berkeley and was convinced that every effort should be made to build a bomb using either uranium 235 or plutonium 239. Over the summer, he had learned that John Cockcroft, using the cyclotron at Cavendish Laboratories, had obtained uranium 235 and had persuaded the British uranium committee of its merit in a “superexplosive bomb.” Moreover, Mark Oliphant, another of Britain’s radar pioneers, was now confident that a U-235 bomb was within the realm of possibility. During a visit to the Rad Lab late that autumn, he told Lawrence of the growing conviction among British scientists that if he tackled the uranium problem, real progress could be made. Lawrence promised Oliphant he would do what he could.
True to his word, early that September Lawrence called Arthur Compton and told him that they had to jump-start an atomic research program—there was no time to lose if America was to win the race for the bomb. “What he was most certain of,” recalled Compton, was “that plutonium 239 could be made in a chain reacting pile and then separated by chemical methods from its parent, uranium 238. His evidence was good. . . .” There was nothing really new in Lawrence’s argument, but it was his absolute confidence in fission as a concrete military weapon, and unshakable faith that it held the key to victory, that gave the program new life. As Compton wrote in his memoir, Atomic Quest, Lawrence’s unique contribution “was a feasible proposal for making a bomb. No one else ever proposed the possibility. He came forward with what he felt could be carried through, and had something tangible to take hold of.”
Not long after that phone call, Lawrence, Conant, and Arthur Compton gathered before the fireplace in Compton’s Chicago home. Lawrence outlined the Berkeley experiments that indicated a bomb could be made with only a few kilograms of fissionable material, either uranium 235 or plutonium. He described the various ways uranium separation could be achieved and argued in favor of pursuing several lines of investigation simultaneously. Every effort should be made to further Fermi’s pile experimentation and plutonium production at Columbia, while he continued testing the more expensive technique, magnetic separation, using the mass spectrometer at Berkeley. Conant, who like Bush tended to err on the side of caution when it came to fission, weighed in on the need to concentrate on projects that were certain to be useful and the importance of not wasting their resources on such an unproved assumption. But after an impassioned speech by Lawrence, assisted by Compton’s reports of Nazi efforts already under way, Conant came around.
Aware of Lawrence’s legendary determination to build a colossal 184-inch cyclotron, Conant was somewhat skeptical of the Berkeley physicist’s assurances that he would commit his laboratory to the effort. Not one to mince words, Conant asked Lawrence point-blank if he was prepared to devote the next several years of his life to the atomic program. The question “brought up Lawrence with a start,” recalled Compton, who never forgot the expression in Ernest’s eyes as he sat there, “his mouth half open.” Lawrence hesitated only a moment—“ ‘If you tell me this is my job, I’ll do it.’ ” With those words, he signaled the start of the race for the bomb.
Typically, Lawrence, with a “damn the torpedoes” enthusiasm even Admiral Farrugut would have admired, threw himself into the uranium work. He gave the project priority over everything else, quickly raising money from Loomis and other longtime patrons. He insisted on bringing in Robert Oppenheimer, a close friend and Berkeley colleague, who was an outstanding theoretical physicist. The only problem was that Oppenheimer was regarded with some suspicion for his union ties—he had tried to recruit faculty members for the American Association of Scientific Workers—and Lawrence had cautioned him more than once to stop his “leftwandering activities.” But Lawrence, who had great respect for “Oppie,” was insistent: “I have a great deal of confidence in Oppie,” he wrote Compton, “and I’m anxious to have his judgment in our deliberations.” His clearance was soon authorized. On October 21, Loomis and Lawrence attended a meeting of the uranium committee—now designated somewhat cryptically as the S-1 Section of the newly formed OSRD—at the General Electric research laboratory in Schenectady. The purpose of the meeting was to discuss how destructive the bomb would be and how much time and money would be required to build it. Oppenheimer estimated that it would take a hundred kilograms of U-235 for an effective explosion. None of Bush’s “hardheaded” engineers on the committee dared even hazard a guess as to the number of years or total cost—somewhere in the hundreds of millions of dollars—involved in building such a weapon.
While the committee struggled to answer those questions to Bush’s satisfaction, Lawrence got to work on modifying and enlarging the thirty-seven-inch cyclotron. On November 6, Arthur Compton personally handed Bush the committee’s report, complete with the calculations by theoretical physicists such as Oppenheimer and Kistiakowsky, acknowledging that “a fission bomb of superlatively destructive power will result from bringing quickly together a sufficient mass of element U-235.” Their recommendation: A full effort to make atomic bombs was essential to the safety of the nation. Roosevelt acted at once and formed a high-level committee to consider the fission bomb proposal, appointing Bush, Conant, Stimson, General Marshall, and Vice President Henry Wallace. Exactly one month later, on December 6, Bush delivered the president’s verdict: If atomic bombs could be made, America had to make them first. Although no record of Roosevelt’s words exists, he made it clear to Bush that he wanted work on the atomic bomb project to be “expedited . . . in every way possible.”
That same day, Lawrence’s newly completed thirty-seven-inch mass spectrograph was used to separate a small amount of U-235, and as he happily reported to Loomis, he was “pushing with the boys” on the isotope separation problem:
I am glad to report that we have already made excellent progress. We have had as large a beam of ions as I anticipated we would be able to produce, i.e. enough to get about a microgram per hour, which is about a hundred times more than others have obtained. We are making some further modifications of the mass spectrograph, and within a few days I hope we will be grinding out a substantial sample.
There is little else to report.
Molly and I privately cherish the hope that we may be able to be with you at Hilton Head [for Christmas]; at least it is pleasant to contemplate the possibility.
On Sunday morning, December 7, 1941, the Japanese hit Pearl Harbor. The following day, December 8, Congress declared war on Japan. The attack immediately unified the country and silenced the isolationists and fission naysayers. Now everyone was focused on a common goal—beating the Nazis to the bomb. America was now at war on two fronts and could not allow the damage done to the country’s pride and naval strength to give hope to their enemies. In the weeks and months after the Pearl Harbor attack, Lawrence worked night and day on perfecting the mass spectrometer to obtain the precious U-235. As he wrote Loomis on December 12, “Now that the war is on I am more anxious than ever to be useful.”
As was by now his habit, he discussed every detail with Loomis, analyzing the various approaches and worrying that time was “too short.” Lawrence was convinced that with hard work and persistence he could overcome any obstacle or find a way around it by means of a new invention, and he was insistent that every potential method be explored, that no possibility be overlooked—“Let’s try them all,” he would tell Loomis as they hunched over his notebooks. He was frustrated at the thought of how much time had been wasted on policy debates, and as a consequence they now found themselves in a breakneck race against German science. “The one thing he wanted to get was to separate U-235,” recalled Loomis, referring to the many technical problems involved in the electromagnetic separation of uranium. “He invented the ‘calutron’ [an improved method of magnetic separation] when he was sitting in my apartment in New York. He was making sketches.” Lawrence took out a sketch to show him that he had made a week or two earlier when he suddenly said, “ ‘I’ve got a better way,’ ” which, Loomis added, “turned out to be true.”
Their baby—the 184-inch cyclotron—which was under construction in a new hilltop laboratory high above the Berkeley campus, would be converted into a large-scale spectrograph, or “calutron.” The big magnet was erected first and a building hastily constructed around it. It reminded Loomis of his early, heady days of cyclotron electronics, and if it were not for his responsibilities back at the Rad Lab, he would have loved to stay and be part of the excitement. In May 1942, the huge spectrograph was turned on for the first time, but it was many months still before it was successfully separating the isotopes. Lawrence’s cyclotroneers worked 365 days a year for the next three years to invent around the difficulties and make the calutron work. His fantastic mass spectrograph would become the basis of hundreds of other calutrons soon to be built and became the main method of producing uranium 235 for the first atomic bomb. Arthur Compton headed a parallel program to breed plutonium in quantity at the Metallurgical Laboratory in Chicago. Fermi would run the newly formed Argonne Laboratory, testing the graphite bars and uranium slugs to be used in the reactors. Everyone who was available pitched in to help, and it is safe to say there was not a single unemployed physicist in the country.
To make enough uranium and plutonium fast enough required a herculean effort. Using his uncommon talents as a leader and indomitable energy, Lawrence began the process of staffing a mass spectrometer plant in Oak Ridge, Tennessee, hiring bright young graduate students left and right and once again robbing Loomis’ Rad Lab of skilled men. In only a short time of frenzied activity, he managed to build up a large-scale operation. Lawrence’s long-standing friendship with Loomis allowed for an unprecedented and continuous exchange of talent and ideas between their two scientific divisions, particularly as many of the physicists at MIT were drafted to work at Los Alamos. “The fact that Lawrence was a member of this radar section aided in maintaining the cooperation between the radar and nuclear programs,” wrote Arthur Compton. “Such cooperation became essential to the completion of atomic weapons.”
As Alvarez reflected years later, it was a great stroke of luck for the country that Loomis was involved in the uranium project from the beginning, not as an originator of ideas so much as an individual who knew how to exploit them, and his actions would contribute to “the remarkable lack of administrative roadblocks experienced by the Army’s Manhattan District, the builders of the atomic bombs.” This “smooth sailing,” he wrote, “was due in large part to mutual trust and respect the Secretary of War and Alfred had. Alfred was in effect Stimson’s minister without portfolio to the scientific leadership of the Manhattan District—his old friends Ernest Lawrence, Arthur Compton, Enrico Fermi, and Robert Oppenheimer.”
1. In nuclear chemistry, as explained by Arthur Compton in Atomic Quest, when a U-238 nucleus catches a neutron, its mass is increased by one unit, becoming U-239. But the nucleus is radioactive and emits an electron with a charge of minus 1 and of very small mass. The loss of one unit of negative charge increases the atomic number from 92 to 93, while the atomic weight remains unchanged at 239.