Exploding Wire Method

Exploding Wire Method (also known as EWM) is a high energy density process by which a rising current is applied to a thin electrically conductive wire. The heat vaporizes the wire, and an electric arc over that vapor creates a shockwave and explosion. Exploding Wire Method is best known to be used as a detonator in nuclear munitions, high intensity light source, and production method for metal nanoparticles.

Exploding Wire Method has a surprisingly long history for a process only recently appropriated. Progress on the comprehension of the mechanism was intermittent, and even at present day there are many aspects that remain not fully understood.

One of the first documented cases of using electricity to melt a metal occurred in the late 1700s and is credited to Martin van Marum who melted 70 feet of metal wire with 64 Leyden Jars as a capacitor. Van Marum's generator was built in 1784, and is now located in the Teylers Museum in the Netherlands. Years later, Benjamin Franklin vaporized thin gold leaf to burn images onto paper. While neither Marum nor Franklin actually incited the exploding wire phenomenon, they were both important steps towards its discovery.

Edward Nairne was the first to note the existence of the exploding wire method in 1774 with silver and copper wire. Subsequently, Michael Faraday used EWM to deposit thin gold films through the solidification of vaporized metal on adjacent surfaces. Then, vapor deposits of metal gas as a result of EWM were studied by August Toepler during the 1800s. Spectrography investigation of the process, led by J.A. Anderson, became widespread in the 1900s. The spectrography experiments enabled a better understanding and subsequently the first glimpses of practical application. The mid 20th century saw experiments with EWM as a light source and for the production of nanoparticles in aluminum, uranium and plutonium wires. Congruently, Luis Álvarez and Lawrence H. Johnston of the Manhattan Project found use for EWM in the development of nuclear detonators.

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