The Chicago Chain Reaction Laboratory was named the "Metallurgical Laboratory", but there was not a single metallurgist in it. After moving from New York to Chicago, the height of the reactor increased, but it still did not have the desired effect, and Fermi thought that graphite, a porous substance, has a lot of air in it, and the nitrogen in the air plays a role in absorbing neutrons, and if it can create a vacuum around the reactor, it may increase the reactor's ability. Inspired by canned food, Fermi asked a blacksmith at Columbia University in Chiga to build a huge iron can and extract the air inside, but the neutron escape was still severe. It was suggested that methane should be used instead of air, but methane was at risk of exploding, and Fermi's lab had already had two dangerous explosions (one with thorium and one with beryllium and radium), and he finally rejected the idea and decided to build a larger reactor.

The ideal place Compton found for the reactor was an indoor tennis court under the West Stand of Columbia Collegia Stadium (Stagg Stadium) in Chiga, a room 9 meters wide, 18 meters long, and nearly 8 meters high, which had been abandoned since the United States entered the war. Physicists wanted a bigger space, but several other places that were more suitable for installing reactors were requisitioned by Chicago's growing military department.

While the new reactor waited for graphite and uranium, Fermi's assistant, Anderson, went to Goodyear Tire & Rubber to order a square balloon, and the Goodyear people glared at the slender young man with amazement, because they had never heard of a square balloon. After Anderson gave the precise specifications, Goodyear reluctantly agreed to make a square balloon out of gelatinized fabric, but Goodyear "can't guarantee that this thing will fly."

Fermi didn't need to make it fly. Two months later, the giant balloon was transported to Columbia University in Chiga, and Fermi's team moved it to an indoor tennis court, where it was secured with scaffolding and lifts, leaving only a fan-shaped hanging door for personnel to enter and exit, and then began assembling the reactor inside. From the countless tests that have been completed, Fermi has an idea of what the reactor should look like: it is a 7.9-meter-diameter balloon supported by a square wooden frame and covered with the square balloon. The balloon was used to create a vacuum when necessary, although the Fermi team never did so. Middle school students who volunteered to help traveled between the indoor tennis court and the nearby carpentry shed, bringing in the finished pieces of wood and taking with them the drawings for the next piece of wood support. When the physicists began fiddling with the pure graphite bricks sent by Union Carbide, everything turned black: first the walls of the tennis court and the balloon, then the ground, where graphite powder covered the floor, smooth as the floor of a ballroom, with black figures gliding over it, their work suits and goggles pitch black. Inside the balloon, a tall black graphite wall is growing rapidly, with seven cadmium rods and three boron steel rods stuck in the wall to control the number of neutrons proliferating.

As the reactor grew taller, Fermi carried out various tests, but the top layers of the graphite ball were never added, because the reactor reached its critical size sooner than expected, only six weeks after the first layer of graphite bricks was placed, in the early morning of December 2. Anderson was the one who did the tail sweeping of the reactor, and if he had pulled out the cadmium rod at that time, he would have started the nuclear reactor, thus becoming the first person in the United States to achieve an artificial self-sustaining chain reaction, but he decided to give this honor to Fermi.

After dawn, Fermi, Compton and their assistants gathered on the tennis court, patiently waiting for the last moment. One of those present was a figure other than the "metallurgical laboratory": Crawford of the DuPont consortium? Mr. Greenwalt, who later became chairman of DuPont, happened to be in a meeting with senior military officials in a nearby room with the rest of DuPont in the early morning of that historic day, and Compton pulled him out and led him to the scene.

The Greenwalt and DuPont folks were in a dilemma: they didn't know how to make a deal with the military. The United States took over the "Uranium Project" in August 1942 and named it the "Manhattan Project". In September, US Army Engineer Colonel Groves was appointed head of the "Uranium Program" or "Manhattan Project". The project encompasses much more than nuclear research, including the production of graphite and uranium (both metallic uranium and uranium oxide), as well as the separation of uranium isotopes, and the production of a new element, plutonium. When DuPont was told that the fission process of uranium produced plutonium, which might be suitable for the atomic bomb, Greenwalt and his colleagues were invited by the military to the University of California, Berkeley, to see the plutonium research work that had been completed, and then flew to Chicago to negotiate with the military about building a nuclear reactor for the production of plutonium. Greenwalt was hesitant to accept the contract, which was worth more than a billion dollars and his company was willing to help win the war, but ...... This is talking about reactors and plutonium! Hell knows what it is!

Compton, sensing Greenwalt's hesitation, decided to break the mold and pull him on the tennis court so he could see the reactor's first run. Compton believes that Greenwalt's younger age "can tell this extraordinary moment to posterity in the longer years." They ascended to the stands at the north end of the tennis court, where Fermi and his assistants were there, in addition to the three people who stayed on the reactor. The three young men were called "suicide squads" and were tasked with pouring barrels of cadmium solution into the reactor as soon as the chain reaction got out of control. And there's another one named George? Vail's young physicist stands next to a cadmium rod on the ground. The other cadmium rods and boron rods have long been withdrawn, and now the whole chain reaction is stopped by this cadmium rod.

The show began. Vail pulled the cadmium rod out a little, and it still had 13 feet left in the reactor, and the Geiger counter began to "click", and the pen moved up a little, drawing a straight line on the roll paper. Fermi gave more instructions, and each time Vail pulled the rod out a little more, the pen rose to the point that Fermi had precalculated, which represented the magnitude of the k-coefficient. Greenwalt gasped nervously, while Fermi smiled calmly, because he had calculated in advance, even if the cadmium rod was completely withdrawn at once, he could guarantee that the reactor would be able to start reacting at a predetermined rate, and according to the calculations, it was absolutely impossible for the reactor to explode, and it would not get out of control to the point of emitting a lethal dose of radiation. However, people on the tennis court are dealing with something unknown, so it's important to be cautious.

So it was lunchtime, and although no one made a sign of hunger, Fermi announced, "Let's go to lunch!" After lunch, everyone was seated again, and Greenwalt was already very excited. By 3:20 p.m., Fermi said to Vail, "Pump it another 1 foot out." Then he turned to the anxious crowd in the stands and added: "This time it's done." Now the reactor will start a chain reaction. "The k-factor pen went up to 1.00, then 1.01, then 1.02, 1.03...... On 1.09 and 1.10, the three members of the "suicide squad" tensed their muscles and waited for Fermi to give instructions. The group stared at the recorders for 28 minutes, the k-factor stabilized between 1.09 and 1.10, and the reactor behaved as expected.

Eugene? Wegener pulled out a bottle of Italian Chianti wine hidden behind him and toasted Fermi. All those present drank wine, using paper cups, silently, without toasting. Then everyone signed the label of the bottle and went away. Greenwalt rushed back to the room where he was talking to the military and announced, "Yes, it was perfectly appropriate for DuPont to start building the reactor as the military asked." "The reactor is an amazing thing, it walks as accurately as a Swiss watch, and with competent scientists like Fermi and his team, DuPont is not taking unnecessary risks. Compton rushed back to his office and made a long-distance call to Connant, a member of the Directorate General for Scientific Research and Development and president of Harvard University. The good news was reported.

The Uranium Advisory Board, which includes representatives of the National Bureau of Standards, the Army and the Navy, meets regularly with physicists and chemists to discuss the development of atomic energy and weapons. Based on the comments made during the discussions, the commission requested appropriate summons from the Army and Navy for the purchase of research materials. After it was reported that the Kaiser Wilhelm Institute for Physics in Germany had undertaken a huge research program on uranium, the "National Defense Research Committee" was established, with OSRD Administrator George W. Bush concurrently serving as its chairman, and the Uranium Advisory Committee became a branch of the association. The Defence Research Council works through contracts with a number of universities and colleges, initially using funds allocated by the Army and Navy and later receiving a dedicated budget from the Congressional Appropriations Committee. Later, because the "uranium program" had become extremely important, Bush decided to let the uranium advisory board (now renamed the S-1 committee) separate from the jurisdiction of the NDRC and directly put it under the management of the OSRD. Bush discussed with Roosevelt the issue of military atomic energy, obtained Roosevelt's approval in expanding the program, adjusting the organization, obtaining special funding, and exchanging intelligence with Britain, and then created a top policy group for the atomic bomb program, which included the president himself, Vice President Wallace, Secretary of War Stimson, and Chief of Staff Marshall and Dr. Connant.

Since all the research work carried out in the laboratory in the United States is to use uranium-235 to achieve a controlled chain reaction. Uranium-235 is a rare isotope found in only 0.7% of natural uranium. In Fermi's nuclear reactor, nuclear fission was achieved with 0.7% uranium-235, and if it could be purified from natural uranium and the heavier uranium-238 could be removed, the chances of fission would be greatly enhanced. According to Fermi's estimates, it may take a few kilograms to dozens of kilograms of uranium-235 with a purity of more than 90% to achieve a nuclear explosion, but mankind has never obtained even a very small amount of pure uranium-235 before, and it is a fantasy to produce this thing in "kilograms".

However, there is another shortcut: the isotope uranium-239 can be obtained by bombarding uranium-238 with high-energy neutrons, which has a half-life of about 23 minutes, and then transmutes into a new element, 93 (neptunium), an unstable transuranic element that decays into plutonium in 2 to 3 days. In March 1940, a research team led by Dr. Seaborg at the University of California, Berkeley, bombarded uranium-238 with a deuterium nucleus accelerated by a 60-inch cyclotron and obtained plutonium-239. Analysis of this material shows that its critical mass is much smaller than uranium, about 1/5 of the latter when it is also spherical, and the purity is only 10 to 15 percent, so it can be used to make new nuclear fissile material with uranium-238, which is highly abundant in nature.

After the United States became involved in World War II, it terminated its research on atomic power and concentrated its manpower and material resources to speed up the pace of building atomic bombs. At a meeting of the top policymaking group, Bush suggested that nuclear physicists and engineers, who were still in a state of decentralized research at that time, should be concentrated in a certain area to improve efficiency and strengthen secrecy. He recommended that the Army Corps of Engineers oversee the construction work in the area. Shortly thereafter, Dr. Connant reviewed the Bush report and raised the issue of building a production plant. At that time, there were six methods of producing fissile material: centrifugation, gas diffusion, liquid thermal diffusion, and electromagnetic separation of uranium-235, and uranium-238 plus graphite or heavy water reactors to produce plutonium-239.

On June 17, 1942, Bush sent Roosevelt a report on the status of the atomic bomb program, in which he pointed out that it was technically achievable to create nuclear weapons for war and detailed the methods of producing such weapons. Roosevelt approved the report, and the next time the U.S. Army Logistics Chief of Staff, Maj. Gen. Steyer, appointed Engineer Colonel Marshall to oversee the construction of an engineering area to "carry out the Army's responsibilities in the development of atomic energy." From this day on, the "Manhattan Project" was officially launched. Of course, at this time, the project was not called this name, but "Alternative Materials Development Laboratory", until August of that year, one of the project leaders, Colonel Groves, worried that the name would arouse people's curiosity, suggested that it be named after Manhattan, where Colonel Marshall's office was located, and thus the "Manhattan Engineering District" was born.

After a series of negotiations, the U.S. Treasury Department agreed to provide 47,000 tons of silver coins worth more than $300 million and 39,000 tons of silver ingots (a reserve for dollar bills) on the condition that the same amount of silver be returned within six months of the end of the war. The coins and ingots were brought out of the West Point vault and transported under strict protection to the American Metal Refining Company to be minted into short silver bars, which were made into deflector tapes, magnet coils, and similar parts for the manufacture of electromagnets by the Alice-Chalmers Company.

In the first few months of the plant's operation, Groves et al. discovered a series of technical problems: the silver ribbon of the magnet core was too tightly wound, and iron filings were mixed in the circulating oil used for cooling, causing a short circuit in the coil; The rat ran into the vacuum; Birds, storms, lightning strikes short-circuit wires...... In the end, Groves had to strengthen security and waste recycling measures to prevent sabotage by sabotage (such as throwing iron filings into circulating oil), and to require α workshops to be cleaned every four weeks and β workshops every two weeks.

The gas diffusion plant (K-25) started much later than the electromagnetic separation plant, as the S-1 commission prioritized it after the electromagnetic separation plant and the plutonium plant. At the heart of the plant were thousands of graded filtration equipment, each with tubes made of metal membranes, and because of the many state-of-the-art chemical technologies involved at the time, Union Carbide, one of the largest chemical companies in the United States, was appointed as the prime contractor for the production of membranes and cascade filtration equipment, and the diffusion pumps were manufactured by Alice Chalmers. Due to the need for multiple frequencies of power and, more importantly, the fear of damage to the power lines, the K-25 plant did not use power from the Tennessee Valley Authority, but instead built a separate thermal power plant. To ensure safety, there is not a single pore in the hundreds of miles of pipes, which are cleaned surgically before they are put into production, and Groves has a dedicated welding and cleaning shop...... In this way, before going into production, the K-25 plant had already spent $200 million.

The factory has also built a liquid thermal diffusion workshop as an auxiliary means of production for gas diffusion. The Navy then funded the experiment and built an experimental plant at the Philadelphia Navy Yard. It would cost about $2 billion to $3 billion to build a complete system for heat diffusion production, but the process could be used as the first step in obtaining low-enriched uranium, which would be much cheaper. In the summer of 1944, the liquid thermal diffusion plant, codenamed S-50, was opened next to the K-25 plant, which used the steam of the latter, and the latter further enriched uranium from the crude product of the former. In this way, Oak Ridge would have provided enough uranium for the Manhattan Project to build an atomic bomb.

"Plutonium production is achievable with a 99 per cent chance of success and a 90 per cent chance of success for bombs according to the currently mastered process...... In terms of time, assuming continuous all-round support, the first atomic bomb would be handed over in 1944 and 1 per month in 1945 would be achieved...... "Arthur? Compton wrote this in his report to Roosevelt.

(To be continued)