The Role of Fission Devices in Nuclear Weapons

A fusion weapon works by instigating a fusion reaction between two isotopes, typically deuterium and tritium. To get the amount of heat necessary to instigate that reaction, you typically need a fission device with a plutonium or uranium core. There are also two kinds of additional materials which are used to influence the criticality of a fission core. Neutron reflectors and tampers do exactly what they say on the tin. They reflect neutrons, from the core, back at it, thus lowering the amount of fissile mass needed for criticality. An oblong mass of plutonium might be critical, or even subcritical, but will become supercritical if beaten