 In June 1944, Oppenheimer created a dedicated Super Group under Teller, who was made directly responsible to Oppenheimer, and Peierls became head of the T-1 (Implosion) Group.In September, Teller's group became the F-1 (Super and General Theory) Group, part of the Enrico Fermi's new F (Fermi) Division.The new design that von Neumann and T Division, most notably Rudolf Peierls, devised used explosive lenses to focus the explosion onto a spherical shape using a combination of both slow and fast high explosives.