The first Sloika design test , RDS-6s , was detonated in 1953 with a yield equivalent to 400 kilotons of TNT ( 15 – 20 % from fusion ) . Attempts to use a '' Sloika '' design to achieve megaton-range results proved unfeasible . After the United States tested the " Ivy Mike " bomb in November 1952 , proving that a multimegaton bomb could be created , the Soviets searched for an additional design . The " Second Idea " , as Sakharov referred to it in his memoirs , was a previous proposal by Ginzburg in November 1948 to use lithium deuteride in the bomb , which would , in the course of being bombarded by neutrons , produce tritium and free deuterium . In late 1953 physicist Viktor Davidenko achieved the first breakthrough , that of keeping the '' primary '' and '' secondary '' parts of the bombs in separate pieces ( " staging " ) . The next breakthrough was discovered and developed by Sakharov and Yakov Zel ' dovich , that of using the X-rays from the fission bomb to compress the '' secondary '' before fusion ( " radiation implosion " ) , in early 1954 . Sakharov 's " Third Idea " , as the Teller – Ulam design was known in the USSR , was tested in the shot " RDS-37 " in November 1955 with a yield of 1.6 megatons
Ivy Mike
Ivy Mike
Thermonuclear weapon