The Teller–Ulam esign is a nuclear weapon design which is used in megaton-range thermonuclear weapons, and is more colloquially referred to as "the secret of the hydrogen bomb". It is named after two of its chief contributors, Hungarian-born physicist Edward Teller and Polish-born mathematician Stanisław Ulam, who developed the design in 1951. The idea is thought to pertain specifically to the use of a fission bomb "trigger" placed near an amount of fusion fuel, known as "staging", and the use of "radiation implosion" to compress the fusion fuel before igniting it. There are a number of other additions and variations to this idea posited by different sources.