How is the high explosive used in a fission bomb detonated so precisely together? – F, United Kingdom
Most modern nuclear weapons produce a super-critical mass of fissionable nuclear fuel by crushing a sphere of that material with high explosives. As the material’s size shrinks, its density increases and it passes rapidly through critical mass to achieve a highly super-critical mass. Nuclear chain reactions then grow exponentially in the material and huge amounts of energy are released. However, the process of crushing a solid sphere of metal to several times its normal density requires sophisticated high explosives triggered at precisely the right moments. The triggering is done with very high-speed electronic devices and explosive detonators that respond almost instantly to high voltage pulses. Perhaps the most critical components in this system are high speed, high voltage switches known as krytron tubes. Because these devices have limited uses outside of nuclear weapons, their export is tightly controlled and it’s a big news story whenever someone is caught trying to smuggle them outside the United States.