The Los Alamos Primer
On the evening of April 15, 1943, I was called to a meeting with about forty other physicists in what used to be the library reading room of the Los Alamos Ranch School. There was a small blackboard on wheels at one end of the room. Everyone sat down in folding chairs, except Oppenheimer (who we called Oppie) and his assistant Robert Serber. After introducing Serber, Oppie sat down. It was at that moment that my suspicions of the work we were doing were confirmed.
"The object of the project is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast-neutron chain reaction," Serber stated. There was a stunned silence. Even though I had already guessed what we were working on, there were many scientists who hadn't. Then Serber began to explain the physics of the atomic bomb, all the while scribbling on the blackboard. The word "bomb" was mentioned in almost every sentence. Concerned that someone might overhear, Oppie asked John Manley, the physicist sitting next to him, to tell Serber to stop saying "bomb." From then on, Serber referred to the bomb as "the gadget." It stuck, and soon everyone who knew about the bomb called it that.
Over the next two weeks, Serber gave four more lectures describing the physics of how the gadget might work. I already understood much of this because of the work I had done with Enrico Fermi. However, the atomic reactor had only released a tiny amount of energy at a very slow speed. At Los Alamos, we needed to create a much faster chain reaction. One that would release a vast amount of energy and result in a giant explosion. Also, the entire thing had to be transportable by airplane.
Serber explained a possible design for the gadget that we called the "gun assembly" method. Basically, two pieces of uranium could be fired at one another inside a specially developed artillery gun. When the pieces of uranium met, they would form the amount of material needed to get a chain reaction (a critical mass). Within less than a millionth of a second, so many atoms would fission that the lump of uranium would blow itself apart with extreme force. Surrounding the uranium would be a tamper, or a sheet of very dense metal. Its job would be to contain the neutrons and bounce them back into the uranium, causing more fission and a bigger explosion.
We still had many questions. How much material was needed to form a critical mass? What would we use as a tamper? Would the design even work? So we got to work.
From Serber's lectures, the Los Alamos Primer was written. Every new scientist was expected to read it as soon as they arrived.
On the evening of April 15, 1943, I was called to a meeting with about forty other physicists in what used to be the library reading room of the Los Alamos Ranch School. There was a small blackboard on wheels at one end of the room. Everyone sat down in folding chairs, except Oppenheimer (who we called Oppie) and his assistant Robert Serber. After introducing Serber, Oppie sat down. It was at that moment that my suspicions of the work we were doing were confirmed.
"The object of the project is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast-neutron chain reaction," Serber stated. There was a stunned silence. Even though I had already guessed what we were working on, there were many scientists who hadn't. Then Serber began to explain the physics of the atomic bomb, all the while scribbling on the blackboard. The word "bomb" was mentioned in almost every sentence. Concerned that someone might overhear, Oppie asked John Manley, the physicist sitting next to him, to tell Serber to stop saying "bomb." From then on, Serber referred to the bomb as "the gadget." It stuck, and soon everyone who knew about the bomb called it that.
Over the next two weeks, Serber gave four more lectures describing the physics of how the gadget might work. I already understood much of this because of the work I had done with Enrico Fermi. However, the atomic reactor had only released a tiny amount of energy at a very slow speed. At Los Alamos, we needed to create a much faster chain reaction. One that would release a vast amount of energy and result in a giant explosion. Also, the entire thing had to be transportable by airplane.
Serber explained a possible design for the gadget that we called the "gun assembly" method. Basically, two pieces of uranium could be fired at one another inside a specially developed artillery gun. When the pieces of uranium met, they would form the amount of material needed to get a chain reaction (a critical mass). Within less than a millionth of a second, so many atoms would fission that the lump of uranium would blow itself apart with extreme force. Surrounding the uranium would be a tamper, or a sheet of very dense metal. Its job would be to contain the neutrons and bounce them back into the uranium, causing more fission and a bigger explosion.
We still had many questions. How much material was needed to form a critical mass? What would we use as a tamper? Would the design even work? So we got to work.
From Serber's lectures, the Los Alamos Primer was written. Every new scientist was expected to read it as soon as they arrived.
The Tech Area
The Tech Area was only half-finished when we began working in it. It contained our labs and offices, and was surrounded by a nine-foot, barbed wire fence. There was only one gate, and it was guarded by military personnel 24/7. To get in, I had to show my white badge- a special kind of picture ID that only the scientists were given.
We were organized into divisions in order to solve all of the apparent problems. I worked with a group on measuring the nuclear properties of the isotopes uranium-235 and plutonium-239. Oppie was a miracle. He inspired us to do things we didn't think we could. Sometimes he would pop into our lab and help solve a problem that we had worked on for a substantial amount of time. Whenever he asked my team for updates, I was the one to write the fifteen to twenty page paper describing our recent efforts. He would say, "Well, let's look this over and we'll talk about it." After taking about five minutes to flip through the pages, he would discuss the paper's key points with me. His ability to absorb information was remarkable. I think he was fully familiar with everything of any significance happening in the lab.
I worked a 10 to 12 hour day, Monday through Saturday. We had Sundays off to rest and recharge. I often went on hikes in the nearby mountains, and sometimes I went fishing.
The Tech Area was only half-finished when we began working in it. It contained our labs and offices, and was surrounded by a nine-foot, barbed wire fence. There was only one gate, and it was guarded by military personnel 24/7. To get in, I had to show my white badge- a special kind of picture ID that only the scientists were given.
We were organized into divisions in order to solve all of the apparent problems. I worked with a group on measuring the nuclear properties of the isotopes uranium-235 and plutonium-239. Oppie was a miracle. He inspired us to do things we didn't think we could. Sometimes he would pop into our lab and help solve a problem that we had worked on for a substantial amount of time. Whenever he asked my team for updates, I was the one to write the fifteen to twenty page paper describing our recent efforts. He would say, "Well, let's look this over and we'll talk about it." After taking about five minutes to flip through the pages, he would discuss the paper's key points with me. His ability to absorb information was remarkable. I think he was fully familiar with everything of any significance happening in the lab.
I worked a 10 to 12 hour day, Monday through Saturday. We had Sundays off to rest and recharge. I often went on hikes in the nearby mountains, and sometimes I went fishing.
The First Gadgets
By early 1944, we had created two gun assembly models. The gadget "Thin Man" used plutonium-239, and the smaller and lighter "Little Boy" used uranium-235. We finally felt close to achieving our goal. Then everything changed. Emilio Segrè discovered that the design of Thin Man was hopelessly flawed. The gun method would fail to create the desired explosion using plutonium. We had already been worried about receiving enough uranium-235 from the plant in Oak Ridge, Tennessee to power Little Boy, so we certainly didn't have enough to replace the plutonium in Thin Man.
Everyone began searching for a solution to this enormous setback. Physicist Seth Neddermeyer and mathematician John von Neumann devised another bomb model based on implosion technology. A sphere of plutonium would be surrounded by small explosives. When they were detonated, they would squeeze the plutonium and set off a nuclear chain reaction. We were less certain of this design, but we were desperate, so we gave it a go. The new gadget design was called "Fat Man," in honor of Winston Churchill.
By early 1945, prospects were bright again. Field tests confirmed that Little Boy would be ready for use by August 1st of that year. In February, Fat Man's design was approved, and the plants in Oak Ridge and Hanford were back on track. They began sending us fissionable material that spring. Once again, I was optimistic.
By early 1944, we had created two gun assembly models. The gadget "Thin Man" used plutonium-239, and the smaller and lighter "Little Boy" used uranium-235. We finally felt close to achieving our goal. Then everything changed. Emilio Segrè discovered that the design of Thin Man was hopelessly flawed. The gun method would fail to create the desired explosion using plutonium. We had already been worried about receiving enough uranium-235 from the plant in Oak Ridge, Tennessee to power Little Boy, so we certainly didn't have enough to replace the plutonium in Thin Man.
Everyone began searching for a solution to this enormous setback. Physicist Seth Neddermeyer and mathematician John von Neumann devised another bomb model based on implosion technology. A sphere of plutonium would be surrounded by small explosives. When they were detonated, they would squeeze the plutonium and set off a nuclear chain reaction. We were less certain of this design, but we were desperate, so we gave it a go. The new gadget design was called "Fat Man," in honor of Winston Churchill.
By early 1945, prospects were bright again. Field tests confirmed that Little Boy would be ready for use by August 1st of that year. In February, Fat Man's design was approved, and the plants in Oak Ridge and Hanford were back on track. They began sending us fissionable material that spring. Once again, I was optimistic.