The Story of The First Atomic Bomb, Trinity Test and the First Atomic Bomb Plutonium
This is the photograph of a tower, which is currently 80 years old, on which you see some people mounting a giant ball-shaped object.
Do you know what this is?
It is the first massive nuclear explosion in the world.
Today, being July 16, 1945, at 5.29:45 am, the desert of New Mexico was illuminated by a shocking flash, and then a great explosion that was to mark the dawn of the nuclear era.
This was the Trinity test, the climax of years of covert scientific labor in the Manhattan Project and the baking of the first nuclear bomb in the history of the world.
The Gadget: A plutonium implosion bomb:
The atomic weapon was a complicated type of fission bomb called Plutonium Implosion, and a companion nuclear bomb known as Fat Man, was dropped in Nagasaki just under one month later on August 9. The type of implosion was an important technical challenge over the basic "gun-type" uranium bomb, yet it was much more efficient, and permitted the use of plutonium, an easier-to-produce fissionable material.
What was the mechanism of the plutonium bomb?
To interpret The Gadget, one has to be aware of the concepts of nuclear fission. Fission is the splitting of the nucleus of a heavy element like uranium-235 or plutonium-239 into other smaller nuclei, releasing a great deal of energy and a large number of neutrons. When these emitted neutrons hit other fissionable nuclei, they can cause further fission, and a self-sustaining chain reaction begins.
To generate a nuclear explosion and sustain it is the difficulty in attaining and maintaining a supercritical mass. A subcritical mass of fissionable material is that in which there are excessively many neutrons that escape, making a sustained chain reaction impossible. But the highly critical mass is considered so dense that a chain reaction can be generated at a very high rate, and it results in an explosion.
The Gadget bomb (shaped in the form of a round ball) had a central sphere of plutonium-239. All sides of the plutonium sphere were enclosed with a specially designed set of highly explosive lenses called the Explosive Lenses. These lenses were organized around the plutonium sphere to ensure that when they were all blown up, they would cause a shock wave to propagate inwards at the same time.
The plutonium sphere was compressed very quickly due to the huge pressure of the explosion of these conventional explosives. This compression made the plutonium much denser, drawing the atoms of plutonium closer to one another. The plutonium became supercritical when the density was attained.
This is the density of plutonium at which, in case it is bombarded with neutrons, the chain reaction of fission may easily proceed. This was at a supercriticality when a small Neutron Initiator (polonium-beryllium), already inserted in the core, gave out a shower of neutrons, which instantly commenced the chain reaction.
When it began, the chain reaction acquired an unbelievable pace. The neutrons produced in the first fission struck the other plutonium nuclei and caused them to fission, also emitting more neutrons, which caused a fast growth of fission.
The whole process (initiating the chain reaction to the emission of the majority of the energy of the bomb) took tens of nanoseconds. The enormous amount of energy emitted quickly heated and expanded the plutonium, returning it to a subcritical state, and when the material itself started to disintegrate, the chain reaction was effectively terminated.
This was an enormous engineering and scientific feat that saw the success of this extremely intricate and accurate implosion design.
The experiment day: Watching the unthinkable
The period before the Trinity test was full of anxiety for all. Even the then director of the bomb-making facility, Robert Oppenheimer, found the idea concerning, and was burdened by years of hard work and political pressure. It was also a worrying day with thunderstorms threatening to postpone the much-needed experiment. However, at the beginning of the predawn of July 16, 1945, the skies started clearing.
Some of these scientists, military men, and government officials had assembled at a number of observation bunkers, which were miles away at a distance of Ground Zero, where The Gadget was installed on a steel tower of 100 feet. It was the mood of terror, expectation, and profound historicity.
Some of the most brilliant minds, who had been devoted to the Manhattan Project over the years, were among the most prominent scientists of that era:
J. Robert Oppenheimer: Scientific Director of Los Alamos Laboratory, the so-called father of the atomic bomb. His famous quote is,
And now I am Death, the slayer of worlds,
Who else was there?
Italian Nobel laureate Enrico Fermi was a pioneer in nuclear reactors. Richard Feynman, an eccentric and brilliant young physicist, was another big name. Feynman was in the control bunker watching what was happening. Then followed James Chadwick, the Nobel laureate who discovered the neutron, whose discovery of the atomic bomb was a wonder today, as the British contribution to the Manhattan Project.
One Nobel laureate physicist, Isidor Isaac Rabi, also worked with Oppenheimer.