tamper

In nuclear engineering, a tamper is a component surrounding the fissile material in a nuclear weapon. Its primary function is to reflect neutrons back into the fissile core, thereby increasing the efficiency of the nuclear chain reaction and allowing for a greater explosive yield with less fissile material.1

The tamper also helps to hold the fissile material together for a longer period during the explosion, further contributing to a more powerful detonation. Common fissile materials used in nuclear weapons include uranium-235 and plutonium-239. These materials are assembled into a supercritical configuration, either through a gun-assembly method or implosion, to initiate a nuclear explosion.12