<P> A thermonuclear weapon is a second - generation nuclear weapon design using a secondary nuclear fusion stage consisting of implosion tamper, fusion fuel, and spark plug which is bombarded by the energy released by the detonation of a primary fission bomb within, compressing the fuel material (tritium, deuterium or lithium deuteride) and causing a fusion reaction . Some advanced designs use fast neutrons produced by this second stage to ignite a third fast fission or fusion stage . The fission bomb and fusion fuel are placed near each other in a special radiation - reflecting container called a radiation case that is designed to contain the energy of the primary charge for as long as possible . The ability of the design to ignite fusion leads to a greatly increased explosive power when compared to first generation single - stage fission weapons ("atomic" bombs). </P> <P> The device is colloquially referred to as a hydrogen bomb or, an H - bomb, because it employs the fusion of isotopes of hydrogen . </P> <P> The first full - scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons . The modern design of all thermonuclear weapons in the United States is known as the Teller--Ulam configuration for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951 for the United States, with certain concepts developed with the contribution of John von Neumann . Similar devices were developed by the Soviet Union, United Kingdom, France, and China . </P> <P> As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above 50 kilotons of TNT (210 TJ), virtually all the nuclear weapons of this size deployed by the five nuclear - weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using the Teller--Ulam design . </P>

When was the first weapon ready thermonuclear bomb tested