The Gadget Test (1945)

This photograph was taken on July 15, 1945. The man standing beside this device is Norris Bradbury who was described by someone several years ago as the mechanic who had helped assemble the device (not completely inappropriate, but that "mechanic, Norris Bradbury, had a doctorate in physics and went on to become the second Director of the Los Alamos Nuclear Laboratory). The device was referred to as "The Gadget," and it consisted of a collection of carefully assembled explosive lens arranged in a spherical pattern much like the outlines commonly seen on volleyball. Early the next morning, on July 16, 1945, those conventional explosives were detonated simultaneously and resulted in a highly symmetrical pressure wave that literally imploded a small spherical chunk of metallic plutonium. There was a very small hollow spot in the center of that chunk of plutonium containing two elements that when crushed together released neutrons triggered plutonium nuclei to split (or fission) into two fragments and releasing energy. That relatively small sphere then released in total the equivalent of nearly 10,000 tons of TNT. It was the first man-made nuclear explosion and was conducted at Alamogordo in New Mexico and was referred to as the Trinity test.

.

The device was identical in concept and general configuration to the weaponized version of the bomb dropped on Nagasaki on August 9, 1945.

.

The reason for the July 16 test was to confirm that the implosion weapon would work. The first bomb dropped on Hiroshima (on August 6, 1945) in Japan was a uranium "gun-type" device that the developers had no doubt would work.