Friday, August 03, 2007


The interior of an 18" square x 1" piece of Plexiglas was charged to 2.2 million volts (MV) using a 5 MV particle accelerator. A layer of excess electrons become trapped deep inside, When discharged, the excess charge escaped with a bright flash and a loud bang. The hot, lightning-like discharge created thousands of microscopic fractures inside the acrylic, resulting in a branching "Captured Lightning" sculpture (or Lichtenberg Figure).

The branching, self-similar patterns observed in Lichtenberg figures exhibit fractal properties. Lichtenberg figures often develop during the dielectric breakdown of solids, liquids, and even gases.

Two-dimensional (2D) Lichtenberg figures can be produced by placing a sharp-pointed needle perpendicular to the surface of a non-conducting plate, such as of resin, ebonite, or glass. The point is positioned very near to, or in contact with, the plate. A source of high voltage, such as a Leyden jar (a type of capacitor) or a static electricity generator, is applied to the needle. This creates a small electrical discharge to the surface of the plate.

Another type of 2D Lichtenberg Figure can be created when an insulating surface becomes contaminated with semiconducting material. When a high voltage is applied across the surface, leakage currents may cause localized heating and progressive charring of the underlying material. Over time, branching, tree-like carbonized patterns are formed on the surface of the insulator called electrical trees. These may ultimately bridge the insulating space, leading to catastrophic failure of the insulating material.

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