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CHAPTER 1
BIG NEWS: NUCLEAR FISSION RELEASES NEUTRONS!
In the beginning, the headwaters of nuclear science lay in territories controlled by the European dictators. The discovery of nuclear fission in Berlin in 1938 triggered intense global interest, but Hitler and Mussolini did not understand what cards they held. They drove away the leaders of “Jewish physics” (i.e., quantum physics and relativity); they favored their own classical and more understandable “Aryan physicists.”
In 1921, Albert Einstein won the Nobel Prize in physics for his discovery of the photovoltaic effect, but a decade later, on the eve of Hitler’s coming to power, Einstein saw the handwriting on the wall. He fled Berlin, settling into Princeton for the rest of his days. Einstein provided the political spark for Roosevelt’s decision to start work on a wartime A-bomb program.
In 1934, Edward Teller, Hungarian by birth, was pulled out of Göttingen, a small university town in central Germany, by a Jewish Rescue Committee. Teller first settled into George Washington University. Later, he moved to Los Alamos, New Mexico, where he, along with others, devised one key A-bomb concept, spherical implosion of a plutonium pit, and, in time, solved the central problem of H-bomb design.
Enrico Fermi was an Italian living with a Jewish wife in Mussolini’s Italy. The intellectual climate at the University of Rome was stimulating, but the political atmosphere was growing heavy. On November 9, 1938, Hitler’s Nazis unleashed the Kristallnacht terror in Germany. To Enrico and Laura Fermi, that was the last straw. The following week they traveled to Stockholm, picked up the professor’s Nobel Prize for work on neutron bombardment of the nucleus, and then kept right on going, to New York. Four years later, Fermi initiated operation of the first chain-reacting nuclear pile at the University of Chicago, thereby opening the door to the production of plutonium and the explosion of Fat Man.
Lise Meitner was Austrian and Jewish by birth. In 1938, as a pioneering and isolated lady physicist, she was working alongside chemist Otto Hahn at the Kaiser Wilhelm Institute in Berlin. Hahn was studying the chemical effects of neutron bombardment of the uranium nucleus. By 1938, Meitner and Hahn had enjoyed a thirty-year professional relationship.
That year started badly, with Hitler’s virulent anti-Jewish policies penetrating even into academia; Meitner’s file made it to the desk of SS chief Heinrich Himmler. In March, the Nazis annexed Austria in a bloodless (actually, highly acclaimed) Anschluss. Meitner’s Austrian passport no longer protected her, since Austria was no longer a country. Her life was in jeopardy; lacking documentation, she found it difficult to emigrate. On July 12, 1938, with the covert assistance of a Dutch colleague and carrying but one suitcase, Meitner fled to Groningen, Holland, and thence to Sweden, leaving behind her long-time German associates and her beloved laboratory.
While living in Scandinavia, Meitner stayed in touch with her German colleagues. In November of 1938 she reconnected with Otto Hahn at a Niels Bohr–sponsored seminar in Copenhagen. Hahn, born in Frankfurt to “acceptable” German stock, had served in a chemical warfare unit during World War I. He remained securely behind, in Berlin, for the duration of the Hitler years.
At the time of their meeting in Copenhagen, Meitner urged Hahn to re-examine the products of his neutron bombardment of uranium. “You have it all wrong,” she observed. “Your theories [of chemical reaction] make no sense.” Hahn returned to Berlin, repeated his experiments, and on December 19 wrote to Meitner that he had found barium in the “reaction products.” How could that be? Barium was far down the periodic table from uranium. “Perhaps you can suggest some fantastic explanation,” he wrote. “Uranium really cannot break into barium.”
Oh yes, it could.
Upon receipt of that letter, on December 21, Meitner and her nephew-physicist, Otto Robert Frisch, began to reflect on Bohr’s model of the nucleus: a drop of liquid, held together by surface tension. If too big, it will pop apart. But how to account for the energy released in the Hahn experiments? According to Einstein’s famous E=MC2, that unexplained energy must have come from the tiny difference of mass, known as the “packing fraction,” as one moves down the periodic table. The following day, Meitner responded to Hahn, advising that the nucleus must have split in two. To explain the phenomenon and the associated release of energy, she coined the word “nuclear fission”.
Hahn received the letter on December 23, 1938, and published soon thereafter. After the war, he and his virulently anti-Nazi coworker Fritz Strassman were awarded the Nobel Prize for the discovery of fission. Meitner spent the war years in Scandinavia, well out of Hitler’s grasp. Her recognition only came decades later, in 1966, when Glenn Seaborg, chairman of the U.S. Atomic Energy Commission and a Nobel laureate himself, awarded the AEC’s Fermi Prize to Hahn, Meitner, and Strassman for their “independent and collaborative contributions to the discovery of nuclear fission.”
Niels Bohr was born in Denmark to a Jewish mother. In 1922, he won a Nobel Prize for explaining the structure of the atom. Seventeen years later, in early 1939, he visited the United States, carrying the news of the Meitner and Hahn discovery of fission and warning of the ongoing atom-splitting work continuing in Berlin. Bohr returned to Denmark in time for the Nazi invasion of western Europe in 1940, staying in Copenhagen until learning, in 1943, that he was about to be arrested. Bohr and his family fled to Sweden in a fishing boat. He and his son were then flown on to England in the bomb bay of a British Mosquito aircraft, traversing the German-controlled airspace over Norway along the way. In time, Bohr made it to Los Alamos, where his presence was so important that, even within the Los Alamos fence, he was given the code name “Nicholas Baker.”
With the growth of Nazi animosity, this westward-flowing tide of nuclear-competent refugees worked its way to Paris, hosted by Irene Joliot-Curie, and New York, welcomed by Fermi. In March 1939, these assemblies of genius in the United States, as well as Soviet readers of the Hahn-Strassman paper in Moscow, confirmed that the lighter-weight fragments resulting from the fission of their parent nuclei needed fewer neutrons for stability. Thus, with every successful neutron bombardment of a uranium nucleus, two or three additional neutrons would be released.1 A chain reaction was possible.
In March 1940, Rudolf Peierls and Otto Frisch, associates at Birmingham University in England, wrote a three-page paper that explained how a uranium fission bomb might be built using U-235. They could have written that paper for Hitler, since Rudolf Peirels had been born in Berlin to Jewish parents. But he fled Germany and immigrated to Birmingham when Hitler came to power. The Peierls-Frisch paper became the basis of the British MAUD Committee report and thus the Allied nuclear weapon program (the membership of the MAUD Committee and the delivery of the report is discussed in chapter 4). Peierls moved on to Los Alamos in 1943.
Wolfgang Pauli was born in Vienna in 1900 to Jewish parents. During the interwar years, he became a superstar in the world of quantum physics, devising the Pauli Exclusion Principle, which explains why all the universe does not collapse back upon itself. In the late summer of 1940, Pauli fled his Zurich enclave for the security of Princeton and the company of Albert Einstein, leaving only his contemporary, Werner Heisenberg, in charge of the German nuclear weapon program. Pauli was awarded the Nobel Prize for physics in 1945.
Nine months after the discovery of nuclear fission, Hitler invaded Poland; World War II was on. The tide of refugees to the West began to flood; in time, much of that talent converged on Los Alamos and Chalk River.2
The Europeans were eager to settle their score with the dictators, inspired as they were by the arrival of yet another Jewish German refugee. Fritz Reiche, arriving in the United States in April 1941, advised his contemporaries that “a large number of German physicists are working intensively on the problem of the uranium bomb under the direction of (Nobel Prize winner) Werner Heisenberg.”3
The mind boggles to think of how different the world might have been if those tyrants in Berlin and Rome had been more hospitable to their native scientific genius.
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CHAPTER 2
LOS ALAMOS: A FIRST, BUT NOT THE LAST
Until the middle of the twentieth century, most atomic and nuclear discoveries had come from European minds, including those of immigrants to the New World. The top seventy nuclear discoveries and innovations of those fifty years1 (1897–1948) originated in:
An examination of the Los Alamos technical staff roster from 1943 to 1945 shows the national origin of the twenty-four intellectual all-stars, i.e., the directors, division chiefs, and their deputies, to have been:
Thus, there never was an American nuclear cartel. Technology does not respect national borders, and in time, nuclear and atomic matters have ceased being even a European monopoly. We should not kid ourselves into thinking otherwise. By the summer of 1942, the European scientific diaspora had temporarily settled into Berkeley, Columbia, and the University of Chicago. Fearing Berlin’s capabilities, these refugees and their American hosts were determined to beat Hitler to the nuclear punch.
In the beginning, nuclear cross-sections were at the heart of the puzzle. What was the probability of a given nuclear response to the bombardment of a nucleus by an incoming particle, usually a neutron? The answer came from experimental measurements. The standard unit of nuclear cross-section, 10-28 square meters, came to be known as a “barn,” from the expression, “bigger than a barn door” (physicist humor, since the dimension was infinitesimally small). Once measured, cross-sections were then used to calculate the progress of a proposed nuclear assembly, chain reaction, or explosion. That data, in turn, was employed to calculate (correctly in the United States) the critical mass of uranium-235.3 The Germans, in Berlin, miscalculated by a factor of ten, leading them to the conclusion that a portable bomb was not feasible.
In Chicago, Enrico Fermi was assembling a large pile of natural uranium (0.7- percent U-235) within a graphite matrix, which was necessary to slow down the cascading neutrons and thus promote their capture by the U-235 nuclei. On December 2, 1942, his “nuclear pile” went critical, producing slightly more neutrons than it consumed during each fission generation. Each neutron’s gestation time was found to be about ten nanoseconds (10-8 seconds), and thus that interval became the unit of time in nuclear work. It was given the name “one shake,” as in “one shake of a lamb’s tail.”
Fermi had created the world’s first chain-reacting nuclear reactor. The secret of his success was the use of ultra-pure graphite. In Berlin physicists were attempting a similar experiment, but they used commercial-grade graphite; their reactor never went critical.
In June 1942, as Fermi labored in Chicago, the German armaments minister convened a conference of scientists, army officers, and munitions experts to review Germany’s nuclear options. Albert Speer wanted to hear about recent nuclear fission developments and then the prospects for an A-bomb on a time scale acceptable to Hitler. Physicist Werner Heisenberg, already a Nobel laureate, led the discussion. He was enthusiastic, but the others, hearing estimates of a nonportable weapon and given no evidence of a chain-reacting experiment, wished to pursue other avenues. Speer closed out the subject in discussions with Hitler on June 23. The Fuehrer preferred to focus on more immediate prospects: rockets and jet aircraft.
Even so, physicists in Germany continued to tinker with nuclear visions for another half year. It was only the destruction of the Norsk Hydro heavy water facility4 in Norway by ten dedicated Norwegian Special Forces paratroopers in February 1943 and the mind-focusing German defeat at Stalingrad during that same month that led Speer to reconfirm, formally, the end of any nuclear weapons work within wartime Germany.
In March 1943, the Allied pace picked up, and the action moved to Los Alamos.5 The scientists relocated to that isolated New Mexico mesa not only achieved awesome scientific breakthroughs, they did so with a breathtaking speed while the engineers at their sides brilliantly coupled those discoveries into the industrial infrastructure and then into the military machines needed to win the war.
Once gathered, the scientists of Los Alamos immediately recognized the possibilities of plutonium as a nuclear weapon material. That element had been discovered by American Glenn Seaborg in Berkeley in March 1941, but it had not even been named when the Los Alamos talent first considered its possibilities. It was clear that “Material 49,” as it was then known, would be a more efficient weapon fuel. Less of it would be needed for a critical mass; more yield would result from a given mass. On the other hand, there were problems. Plutonium generated too many neutrons spontaneously; it could not easily be brought to supercriticality. The solution: a spherical implosion, driven by high explosives, to both rapidly assemble and compress the new metal.
The requirement to accurately implode a ball of fissionable plutonium led to the engineering, machining, and testing of very intricate high-explosive lenses in the canyons of New Mexico. One such partially assembled system is shown in the photo section of this work. High-explosive lens technology was one of the real “secrets of the A-bomb” later appropriated by Soviet spies and Allied scientists after World War II.
Engineers needed to learn the metallurgy of plutonium; no one had ever cast, machined, or even handled this very dangerous metal before. The scientists needed to figure out its equation of state: its hydrodynamics as highly compressed plutonium metal turned into superheated plasma during implosion and compression. Then came the pursuit of neutron generators, the devices needed to flood the assembling core of a nuclear weapon with thousands of initiating neutrons at just the right instant.
These were the cutting edges of A-bomb technology honed in Los Alamos. Equally astonishing was the speed with which those nuclear concepts were brought to tangible reality. It was only at the end of 1941 that governmental papers were signed reflecting a serious U.S. interest in A-bombs. General Leslie R. Groves was not put in charge of the Manhattan Engineering District (as the A-bomb project was called) until September 1942. Fermi’s chain-reacting “nuclear pile” did not go critical until December 1942. Robert Oppenheimer and the first scientific staff members did not arrive in Los Alamos until March 1943. At the earliest, the autumn of 1942 should be considered the starting point for America’s serious efforts to achieve a nuclear weapon. Yet within three years of that start, A-bombs were falling on Japan. Could we make such quick progress today? And what does that tell us about the spe...
