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Oppenheimer's Gamble - The Plutonium Crisis

Mar 18, 2024
thank you, you will not fear it until you understand it this design is the result of a mathematical advance in the face of a

crisis

a year before the first samples of

plutonium

generated in a reactor began to arrive at Los Alamos in a forest service cabin in Pajarito Canyon Lejos from the main laboratory to avoid stray radiation, scientists began counting alpha particle emissions from these new samples. Until then, only microgram quantities of

plutonium

had existed anywhere on the planet. The small samples the scientists had were created at the Berkeley cyclotron. It didn't take them long to realize that there was something terribly wrong with these new, larger samples from the x10 nuclear reactor in Oak Ridge, Tennessee.
oppenheimer s gamble   the plutonium crisis
A 20-microgram sample of the plutonium generated by the cyclotron would record about one count per month. These new, slightly larger samples were wildly different. Recording eight counts in just the first three days of measurement, the implications of these numbers were catastrophic for the Los Alamos project. Oppenheimer called an emergency meeting on the gun-type bomb design that most of laboratories have been developing hundreds of scientists was not going to work. The design was supposed to work by firing one mass of plutonium at another quickly forming a critical mass. Plutonium is otherworldly, as soon as you have enough of it in a single chunk, a critical mass it's basically impossible to stop it from exploding.
oppenheimer s gamble   the plutonium crisis

More Interesting Facts About,

oppenheimer s gamble the plutonium crisis...

A single strain. Neutron is everything. that is required to establish the nuclear chain reaction that detonates the bomb the alpha particle emissions that these scientists were measuring are the result of the spontaneous splitting of unstable plutonium atoms these fission reactions are the same mechanism that drives the bomb they release neutrons which are capable of triggering the detonation, the higher rate of spontaneous fission meant that the weapon-type bomb simply could not bring the two masses of plutonium together quickly enough. A maximum exit velocity of around a thousand meters per second means that it would take around 100 microseconds to spontaneously unite the two masses of plutonium.
oppenheimer s gamble   the plutonium crisis
Fission would likely trigger predestination before the mass was fully assembled, making the bomb a billion-dollar failure. Oppenheimer proposed a risky path forward. A small group of scientists at Los Alamos led by Seth Nettermeyer had been quietly working on a completely different way of building the bomb. It turns out that adding masses is not the only way to achieve plutonium's criticality. The growth rate of the neutron chain reaction that drives the bomb depends on the overall mass but also on the density. If a subcritical mass of plutonium could be quickly squeezed to a higher level. density, could reach criticality to crush a mass of plutonium in microseconds.
oppenheimer s gamble   the plutonium crisis
Nedermeyer's group was developing an implosion bomb design. The idea was to create a controlled explosion around the mass inside a rigid container by directing the force inward and squeezing the plutonium until it reached criticality. However, the first experiments did not go well using steel to simulate the mass of plutonium. Nedermire's group would surround the mass with TNT inside a cylindrical container and ignite the TNT from multiple points iterating through various designs that would invariably end up shattered and twisted into pieces of steel by the force of the explosion (the explosion was not symmetrical enough). As if to compress their masses when he heard Nedermeier's approach, the Los Alamos scientist compared it to squeezing water into your hand and hoping it wouldn't spurt out during Nedermeyer's presentation.
Richard Feynman reported raising his hand from the back row and simply announcing that it sucks months before the

crisis

with brilliant strategic foresight Oppenheimer contacted mathematical genius John Von Neumann to help him with the implosion bomb, he would always have a backup checking the problem and based on the work of others that Von Neumann proposed. A brilliant new design The detonation waves from each of the Nedermeier ignition points propagate in spherical wave fronts. The problem is that when these wave fronts converge on the mass, they do not apply uniform pressure in all directions, causing parts of the mass to squirt out. does not liquefy by general compression monoamen saw a way to redesign explosives so that the detonation waves from each ignition point would be shaped to match spherical plutonium Borrowing mass from optical lens design Von Norman realized that He could shape the wave fronts using an arrangement of high and low velocity explosives; he divided the explosives into individual lenses and within each lens he placed a cone of low velocity explosive within a region of high velocity explosive.
The key idea here is to slow down the more direct paths taken by the detonation wave with just the right amount so that they arrive at the same time as the less direct paths. Mathematically the total travel time between the ignition source and the mass must be the same for all paths the exact shape of the cone can be calculated by solving for the height of the cone as a function of position and depends on the speed of the detonation wave and the slow and fast materials to make this all work in 3D. Von Neumann basically designed a huge football with pentagon and hexagon shaped lenses fitting into a 3D puzzle around the plutonium core.
Oppenheimer knew that Von Neumann's design would work in theory, however, he was well aware of the enormous engineering challenges involved in constructing this complex design. Geometrically complex 3D lenses would have to be formed from new types of high explosives. The lenses would have to turn on with synchronized microseconds. Precision diagnostic equipment. It would need to be designed from scratch to determine whether the experiments were compressing the core, as expected, and even the theory was not entirely sound. Von Neumann's design assumed that the speed of the detonation wave was constant in a given material. Oppenheimer knew this was not true.
The speed of the detonation wave is non-linear and non-local, depending on the shape of the boundary and the overall scale of the lens, it would take the full force of the Los Alamos laboratory to solve these problems in two weeks. Oppenheimer completely reorganized the laboratory to work on implosion tests. It was a big challenge how scientists were able to measure how symmetrically and quickly a given design compressed the core in microseconds when the explosion ended and destroyed the test material. The newly formed X and G division simultaneously followed seven different testing strategies. High-speed X-rays allowed scientists to see inside the bomb as it imploded, capturing changes in density as the detonation wave propagated through the explosive;
However, X-ray methods did not provide good visibility of the compression of the core itself and could only provide a few snapshots of the bomb. Robert's server imploded proposed a clever upgrade instead of having an x-ray radiation source that sends x-rays through the bomb. What about moving a radiation source to the core? The server proposed placing a sample of radioactive lanthanum 140 inside the bomb core. The gamma rays emitted by lanthanum could be measured at multiple locations outside the bomb using ionization chambers and plotted on oscilloscopes that provide continuous data rather than a few snapshots when the bomb imploded as the core compressed, the highest density of the known as sparse experiments, these tests provided some of the most reliable data to guide iteration. of bomb designs, actually executing these tasks was a different matter the source of lantio Very dangerous levels of radiation are emitted.
The server commissioned two military tanks to protect the scientists while they captured data. Each implosion would destroy the ionization chambers and in the first test the server forgot to take into account the fact that the entire forest would burn down and the scientists would have to flee the scene in their tanks. These tests revealed a host of problems with the design. of the bomb the firing of each lens was not well synchronized slight manufacturing differences between the explosive detonation cables connected to each lens led to problematic timing differences on the order of microseconds or more Luis Álvarez led a redesign of the ignition system, changing scan wires to a new electrical detonator design, eventually achieving synchronization within a few hundredths of a microsecond.
Manufacturing explosive lenses presented an enormous range of challenges. Complex molds had to be designed in 3D and high explosives were prone to cracking Bubbles and other imperfections Over a period of 18 months, the lens production plant delivered more than 20,000 lenses to the test sites and many times this amount was rejected due to poor quality, the core of many of these problems was poor mathematical understanding. of the hydrodynamics of detonation waves, no analytical solutions for the governing equations were known. Von Neumann proposed an iterative numerical approach for a Lagrangian formulation of the problem where the pump was modeled as a set of small masses connected by springs for each time step and the position of each mass. depends on its two previous positions and the pressure on the mass half a step away in each direction, starting with boundary conditions based on the Lin shape and the ignition source, the trajectory of the detonation wave can be calculated, This process is time consuming and was done initially. at Los Alamos by human computing groups using mechanical desktop calculators led by Richard Feynman and later performed on IBM punch card accounting machines.
Von Norman's methods were improved by other scientists, but still had limited predictive capabilities, leaving painfully slow iterative trial and error. This approach as the primary path toward a functional implosion design. Months of development led to hard-fought improvements, and by the summer of 1945, scientists at Los Alamos had a design that appeared to be capable of compressing the core quickly and symmetrically enough, although not all test methods. supported this conclusion, testing of the entire device was scheduled for the morning of the Potsdam Conference, which could provide President Truman with valuable information in his negotiations at 5:29 a.m. on July 16, 1945, all science, mathematics and engineering of the Manhattan Project came together in a blinding flash of light in the New Mexico desert, followed by the most violent explosion ever created by man, equivalent to the detonation of 20,000 tons of TNT.
Oppenheimer's

gamble

on the implosion bomb had paid off. Humanity now had the power to destroy itself.

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