The exploding-bridgewire detonator (EBW, also known as exploding wire detonator) is a type of detonator used to initiate the detonation reaction in explosive materials, similar to a blasting cap because it is fired using an electric current. EBWs use a different physical mechanism than blasting caps, using more electricity delivered much more rapidly, and explode in a much more precise timing after the electric current is applied, by the process of exploding wire method. This has led to their common use in nuclear weapons. The slapper detonator is a more recent development along similar lines. History The EBW was invented by Luis Alvarez and Lawrence Johnston for the Fat Man–type bombs of the Manhattan Project, during their work in Los Alamos National Laboratory. The Fat Man Model 1773 EBW detonators used an unusual, high reliability detonator system with two EBW "horns" attached to a single booster charge, which then fired each of the 32 explosive lens units. Description EBWs were developed as a means of detonating multiple explosive charges simultaneously, mainly for use in plutonium-based nuclear weapons in which a plutonium core (called a pit) is compressed very rapidly. This is achieved via conventional explosives placed uniformly around the pit. The implosion must be highly symmetrical or the plutonium would simply be ejected at the low-pressure points. Consequently, the detonators must have very precise timing. An EBW has two main parts: a piece of fine wire which contacts the explosive, and a high-voltage high-current low-impedance electricity source; it must reliably and consistently supply a rapid starting pulse. When the wire is connected across this voltage, the resulting high current melts and then vaporizes the wire in a few microseconds. The resulting shock and heat initiate the high explosive. This accounts for the heavy cables seen in photos of the Trinity "Gadget"; high voltage cable requires good insulation and they had to deliver a large current with little voltage drop, lest the EBW not achieve the phase transition quickly enough. The precise timing of EBWs is achieved by the detonator using direct physical effects of the vaporized bridgewire to initiate detonation in the detonator's booster charge. Given a sufficiently high and well known amount of electric current and voltage, the timing of the bridgewire vaporization is both extremely short (a few microseconds) and extremely precise and predictable (standard deviation of time to detonate as low as a few tens of nanoseconds).