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A Lichtenberg figure is a form of electrical discharge that has a branching, feather-like pattern to it. It is named after a German physicist of the 16th century, Georg Christoph Lichtenberg, who is credited with discovering the pattern. The output generated in a Lichtenberg figure is considered to be a form of fractal, which are patterns in nature that repeat themselves at smaller and smaller scales, demonstrating a property known as self-similarity.
The contemporary science of plasma physics is based upon fundamental principles involved in the creation of branching electrical discharges such as the Lichtenberg figure. The fractals, or electrical treeing of energy that are created when a Lichtenberg figure forms, are due to the physical properties of dielectrics. Dielectrics is the study of electrical breakdown as high voltage currents are passed through an insulator, or a substance that can maintain an electrical field with little power loss.
Xerography, or the process used by photocopy machines, is also based upon the principles of electrostatic discharge first revealed in the Lichtenberg figure. One of the unique aspects of Georg Lichtenberg's work with these figures was that he discovered that positive and negative charges display very different types of patterns. A positively charge figure tends to be heavily-branched and multi-layered, whereas a negatively-charged figure more closely resembles the expanding circular wave pattern one sees when dropping a stone into a pond. Photocopy technology relies upon the difference in positive and negative charges to transmit images to paper.
Originally Georg Lichtenberg used mediums to generate a figure, such as insulators of resin or glass, coated with a thin layer of powdered conductors of sulfur or lead tetroxide. These first displays are known as Lichtenberg Dust Figures. Surface charges appeared in the powder coating not unlike what one sees when iron filings arrange into a pattern in the presence of a magnetic field. The Lichtenberg figure more closely resembled a natural lightning pattern with a more uniform discharge of energy from a circular center branching outward.
As research into the properties of the Lichtenberg figure continued into the 19th and 20th centuries, mediums such as photographic film and ionized gases were later used to display the branching electric discharges. A current method for generating a Lichtenberg figure is to use acrylic plastic blocks as insulators through which a very high voltage, in the 150 kilowatt range, is passed from a linear accelerator. This process generates electron beams of up to 5 million electron volts (MeV), which are capable of penetrating to about 0.5 inch (1.27 cm) into the acrylic base before being stopped. By rotating the acrylic block or charging multiple regions, an elaborate three-dimensional figure can be created. Lichtenberg figure research may have many practical applications in medicine, electronics, and more, and is also a side effect of nuclear fusion research at the Sandia National Laboratory's Z Facility, in New Mexico, United States.