How are atomic bombs made?

Answer 1

Much of the design particulars are top secret-Q but basically you need a mass of fissile material (usually plutonium) large enough to be able to reach supercritical mass and support an uncontrolled nuclear reaction. The explosion is triggered by compressing the plutonium by an implosion to assemble the initially subcritical mass into a supercritical mass rapidly (a couple milliseconds). once the material reaches supercritical mass, a neutron source is fired through it to start the reaction at the optimal time. about 4µs to 7µs later the bomb explodes. The longer the design is able to hold the bomb together, the higher the yield when it does disassemble.