Sick in bed with a bad cold on November 27, Lawrence dictated a congratulatory letter to Compton. But, in Ernest’s eyes, the panel’s final report hardly mattered. “The boys here already have their 37-inch mass spectrograph between the poles of the magnet,” he exulted.12
* * *
While Lawrence understood that transforming a cyclotron into a working uranium separator was not a simple matter, the concept behind the mass spectrograph, at least, was straightforward enough—relying upon the slight but unvarying difference in mass between isotopes to carry out the separation, atom by atom.13
In principle, it was not unlike pitching rocks into buckets. In the spectrograph, an electrically charged beam of ionized uranium atoms bent by a magnet would split into two, carrying U-238 farther from the source than the lighter isotope, U-235, because of the heavier isotope’s greater mass. When the uranium hit the metal collector “bucket,” the ions gave up their charge and the vapor condensed as microscopic flakes of metal. By repeating the process—putting the contents of the closer bucket back into the beam—further concentration, or “enrichment,” of the U-235 would result.14
While the theory was simple, the practical difficulties were many. Since the difference in mass between U-238 and U-235 was barely 1 percent, this translated—even under ideal circumstances—into a separation of 3/10 inch between collectors for a beam with a 4-foot arc. In reality, this distance was almost vanishingly small.
Yet even before the practical problems of separating uranium by this method had been given serious consideration, a seemingly insurmountable theoretical barrier threatened to put an end to the work. The prevailing wisdom was that a powerful, narrowly focused beam would be impossible in a mass spectrograph because of an elemental fact of physics: electrostatic repulsion would force any stream of ions bearing the same charge to spread out, defocusing the beam and making the process unworkable.15
The “space charge” problem had persuaded Nier and Britain’s M.A.U.D. committee that gaseous diffusion remained the most promising method of separating uranium. The Uranium Committee told Princeton physicist Henry Smyth early in 1941 that electromagnetic separation on an industrial scale “had been investigated and was considered impossible.”16 Among physicists, only Lawrence persisted in believing that intuition and an empirical approach could, once again, defeat the pessimism of the theorists.
That faith was to be tested in the coming days and weeks, as Ernest and the boys working on the 37-inch cyclotron oscillated between hope and despair.
But in the early morning hours of Monday, December 1, the rebuilt cyclotron produced the first beam in its incarnation as a mass spectrograph. “Got ions in the 37-inch,” Cooksey laconically recorded in his diary. Berkeley’s beam was already ten times more powerful than that of Nier’s machine.17
* * *
On Saturday, December 6, 1941, Ernest was back in Washington, summoned to OSRD headquarters by Bush to discuss reorganization of what was being called the “S-1 Project.” That morning in Berkeley the new spectrograph had defied the theorists by separating uranium, albeit an almost-infinitesimal amount. Receiving the news by telephone from Cooksey, Lawrence boasted to the new S-1 Committee that the Rad Lab spectrograph was producing a microgram of enriched uranium every hour.18
In truth, the tiny green speck of U-235 left in the near bucket was almost too small to see. Most of the uranium had been smeared around the inside of the machine by the beam. But with the future at stake, Lawrence touted even this meager success as a triumph.
Largely on the strength of Lawrence’s claim, Bush and Conant assigned to him the responsibility for providing the first samples of enriched uranium for later experiments.19
When the meeting broke up at noon, Bush, Conant, and Compton went around the corner for lunch to the Cosmos Club. Realizing that he now had to make good on his commitment, Ernest promptly left for the airport and the next flight west.
By Sunday morning, he was back at the 37-inch. Lawrence and the boys learned of the Japanese attack on Pearl Harbor from the radio that was always left on at the lab. Elsewhere on campus, word spread quickly. Kamen was startled when the normally unflappable Seaborg burst into the Faculty Club reading room in an agitated state. Cooksey, enjoying a weekend sail on the Bay, did not hear of the attack until he returned to the marina. Oppenheimer received the news at home, where he was sleeping late after attending a benefit for Spanish civil war veterans the night before.20
At the Rad Lab that evening, the first visible traces of shiny uranium metal began accumulating in the spectrograph’s collectors. The uranium in the near bucket was five times richer in U-235 than the far collector. That night, after most of the cyclotroneers had gone home to be with their families, Lawrence stayed behind, filled with what he later described as a mixture of hope and foreboding, walking the perimeter fence until nearly dawn.21
Bleary-eyed, he called the boys together on Monday morning to announce that henceforth any work not directly related to defense would be immediately suspended.22 Later, he sent telegrams and worked the phones, pleading with Rad Lab alumni at colleges and universities across the country to return to Berkeley. A great many not only answered the call but brought their own acolytes with them. Ernest persuaded the campus representative of Realsilk Hosiery, a company that hired student salesmen, to become the lab’s recruiter for nonscientific personnel. For the first time, a guard—a young law student—was stationed at the bottom of the road up to Cyclotron Hill, armed with a .410 shotgun borrowed from Cooksey.23
Back in Washington by mid-December, Lawrence asked for $400,000 to explore electromagnetic separation for the next six months. His request was the first made to the S-1 Committee in wartime. In a measure of how much things had changed since Pearl Harbor, it was approved promptly and virtually without discussion.24
The funds would be used to build the prototype of a production mass spectrograph five times the 37-inch in size. Even as he returned, discouraged, from
