The Classical Super is Improved
Meanwhile, Klaus Fuchs continued to work on the American bomb design. In the spring of 1946, Fuchs and John von Neumann contemplated how to improve the classical Super's conditions of initiation and considered using a gun-type primary atomic bomb. They proposed applying a new initiation system in the classical Super that incorporated a secondary core of liquid deuterium-tritium (D-T) mixture, which would be heated, squeezed and ignited by the energy of radiation from a primary atomic bomb. Fuchs came up with the idea of transferring the D-T mixture out of the uranium-235 into a radiation-heated beryllium oxide tamper. To confine the radiation within the tamper volume, he suggested enclosing the system in a radiation-impervious casing. Thus was born the radiation implosion principle.
Fuchs' design, noted as far ahead of its time, was the first physical scheme to utilize the radiation implosion principle and served as the prototype for the future Teller-Ulam configuration. On May 28, 1946, Fuchs and von Neumann jointly filed a patent application for the invention of a new scheme for the initiator of the classical Super using radiation implosion.