Exploding-bridgewire detonator

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.

[2][3] 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.

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.

Given a sufficiently high and well-controlled 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).

[4] EBWs have found uses outside nuclear weapons, such as the Titan IV missile,[5] safety conscious applications where stray electrical currents might detonate normal blasting caps, and applications requiring very precise timing for multiple point commercial blasting in mines or quarries.

Primary explosives such as lead azide are very sensitive to static electricity, radio frequency, shock, etc.

To achieve the melting and subsequent vaporizing of the wire in time sufficiently short to create a shock wave, a current rise rate of at least 100 amperes per microsecond is required.

The extremely short rise times are usually achieved by discharging a low-inductance, high-capacitance, high-voltage capacitor (e.g., oil-filled, Mylar-foil, or ceramic) through a suitable switch (spark gap, thyratron, krytron, etc.)

A very rough approximation for the capacitor is a rating of 5 kilovolts and 1 microfarad, and the peak current ranges between 500 and 1000 amperes.

When fired, it creates a strong electromagnetic pulse, which is inductively coupled into one or more secondary coils connected to the bridge wires or slapper foils.

A low energy density capacitor equivalent to a compression generator would be roughly the size of a soda can.