While Cousins and Ware began their work, in April 1947 Thomson filed a more complete patent application. This described a larger 4 metres (13 ft) wide torus with many ports for injecting and removing gas and to inject the radio frequency energy to drive the current. The entire system was then placed within a large magnet that produced a moderate 0.15 T vertical magnetic field across the entire torus, which kept the electrons confined. He predicted that a power input of 1.9 MW would be needed and calculated that the D-D and D-T reactions would generate 9 MW of fusion energy, of which 1.9 MW was in the form of neutrons. He suggested that the neutrons could be used as a power source, but also if the system was surrounded by natural uranium, mostly U, the neutrons would transmute it into plutonium-239, a major component of atomic bombs.