Lichtenberg Figures... An ExtraOrdinary Tesla Coil Application! Bert Hickman • Stoneridge Engineering 2523 Stonewall Ave.• Woodridge, IL 60517 [email protected] What Are Lichtenberg figures? surface. The powdered sulfur was Lichtenberg figures are branching, attracted to the positively charged tree or fern-like patterns that form regions and the red lead to negative as the result of high voltage dis- regions, thus making the previous- Doubly Irradiated "Windblown charges on the surface of, or within, ly hidden regions of charge clearly Lightning" Lichtenberg Figure electrical insulating materials (di- visible. This figure was created by irradiating a block of electrics). The first Lichtenberg Plexiglas with a 5 million electron volt electron figures were actually 2-dimensional Lichtenberg also observed that beam on the left side, rotating it 180 degrees and then irradiating it on the right side, thereby creat- patterns formed in dust on the sur- the shapes of the positively and negatively charged figures were ing two independent internal charge layers. The face of charged insulating plates in right charge layer was then manually discharged, the laboratory of their discoverer, significantly different. Positive causing a 3-D "lightning storm" inside the right- German physicist Georg Christoph figures tended to be star-like with most layer, which then spread into a series of dis- Lichtenberg (1742-1799. Professor long branches, while negative fig- charges between the two layers. The specimen ures tend to be round or fan-like. is lit from below by an array of blue LED's. Un- Lichtenberg made this observation like low detail laser crystal art, each Lichtenberg in the late 1700's, demonstrating By carefully placing a piece of specimen has a unique and incredibly detailed the phenomenon to his physics stu- paper onto the dusted surface, he fractal discharge pattern. As they branch, the dents and peers. was able to transfer these image discharge channels become increasingly finer, to the paper, demonstrating what becoming hairlike as they finally disappear. The The basic principles involved in was later to become the process of smallest discharges may ultimately go to the mo- lecular level. (Actual size: 3" x 3" x 2") the formation of these electrostatic Xerography. Drawings of positive figures later evolved to become and negative figures actually cap- searchers used photographic film modern xerography and the science tured by Lichtenberg are shown to directly capture the light emitted of plasma physics. Lichtenberg below. by positive or negative high voltage used electrostatic devices to charge discharges along dielectric sur- Later researchers included Gas- the surfaces of various insulating faces. Von Hippel discovered that ton Planté (mid 1850's), Thomas materials such as resin, glass, or Lichtenberg figures were actually Burton Kinraide (late 1800's), Carl ebonite. He then sprinkled a mix- created through complex interac- Edward Magusson, and Dr. Arthur ture of finely powdered sulfur and tions between ionized gas (corona Von Hippel (1930's+). These re- red lead (lead tetroxide) onto the or electrical discharges) and the di- electric surface below. It was also found that increasing the applied voltage or reducing the surrounding gas pressure caused the length of the figures to in- crease. This property was used in klydonographs, special recording instruments that photographical- ly recorded the size and shape of Lichtenberg figures that appeared during abnormal electrical surges on power lines. Klydonographs allowed lightning researchers and Positive Lichtenberg figure Negative Lichtenberg figure power system designers to esti- EXTRA ORDINARY TE CHN O L O GY - APR/MAY/JUN 2007 27 mate peak voltages and polarity upon the original theories and tech- trons into a high-energy beam. The of abnormal transients caused by niques discovered by Dr. Gross. energy of the accelerated electrons lightning strikes to power lines. A The resulting Lichtenberg figures is measured in millions of electron schematic diagram of the main parts are sometimes called electrical Volts (or MeV). The LINAC that of a klydonograph is shown on the trees, electron trees, beam trees, or we use accelerates electrons to a leftmost drawing above, along with spark trees - we call them Captured kinetic energy of between three and examples of "klydonograms" from Lightning. five MeV. At these energies, elec- equal magnitude positive and nega- How we create our trons leaving the accelerator were tive high voltage transients. "Captured Lightning" sculptures traveling at relativistic velocities Lichtenberg figures are now known We have continued to develop and that are between 98.5% and 99.6% to often occur during electrical refine irradiation and material pro- the speed of light. breakdown processes within most cessing techniques to create a truly As the specimen is irradiated by gases, insulating liquids, and solid unique line of 2D and 3D Lich- the beam, electrons are driven deep dielectrics. Lichtenberg figures can tenberg figure sculptures that we inside the acrylic. The penetration be created very quickly (tens of call "Captured LightningTM". Our depth is determined by the electron nanoseconds) when dielectrics are Captured LightningTM sculptures beam's initial energy, the material's heavily overstressed, or they can are made from specially cut and dielectric properties, and its den- grow very slowly , through a series polished clear plastic (polymeth- sity. The higher the electron beam of low energy partial discharges, ylmethacrylate, or PMMA), also energy, the deeper the penetration. evolving into partially conductive called acrylic, or by various trade As the specimen is irradiated, huge surface patterns or 3D "electrical names such as Lucite, Plexiglas, or numbers of electrons accumu- trees". Electrical trees may form Perspex. Acrylic was selected be- late inside the acrylic, creating a on contaminated insulator surfaces, cause of the combination of crystal stranded, cloud-like layer of excess within dielectrics due to internal clarity, and its superior electrical negative electrical charge called a defects or voids, or at points where and mechanical properties. Other space charge. an insulator has been physically clear polymers, such as polycar- By carefully changing the orienta- damaged. bonate (PC), polystyrene (PS) , tion of the specimens and passing Considerable pioneering research polyethylene terephthalate (PET), them through the beam in two or on the detailed behavior of charge and polyvinyl chloride (PVC) more passes, complex 3-dimen- storage within dielectrics was per- will also work to varying degrees. sional space charge regions can be formed by Dr. Bernhard Gross in Some materials even develop dark, produced. Since acrylic is an excel- the middle of the last century. In the or even black (carbonized), trees. lent dielectric, most of the injected early 1950's, Dr. Gross discovered Our sculptures are created by in- electrons cannot escape, so they that internal Lichtenberg figures jecting acrylic specimens with high accumulate under continued irra- could be created within plastic ma- velocity electrons. Electrons are diation, causing a huge negative terials by injecting them with high tiny, negatively charged particles space charge to develop inside the energy electrons using a linear ac- that orbit the nucleus of the atoms specimen. celerator (LINAC). that make up all condensed matter. As the space charge grows, the The techniques we use to make An electron beam accelerator is resulting electrical field also in- our Lichtenberg Figures are build used to accelerate and focus elec- creases. Eventually, the stress from Schematic view of a klydonograph showing the position of the photographic film and HV electrode. From W.W. Lewis, "The Protection of Transmission Sys- Light from high voltage discharges creates a permanent photographic record of the event. tems Against Lightning", John Wiley & Sons, 1950 28 EXTRA ORDINARY TE CHN O L O GY - APR/MAY/JUN 2007 Electrodes placed on acrylic material s are used to launch the electrons driven deep into the acrylic. Great Reference Books for (Photo courtesy of Theodore Gray) Advanced Researchers may reach hundreds or even thou- as well as Home Schoolers! sands of amperes, causes the Get ALL Three for your Library TODAY! acrylic to melt and fracture along each path, and the higher current Basic Electricity "roots" may even char slightly. The US Bureau exit point of the discharge appears of Naval Personnel as a small hole on the surface of the acrylic. Originally a training course, its the best non- The discharge point is typically lo- technical coverage on electricity. Topics include the huge electric field overcomes cated at a surface defect, or where a point of external mechanical batteries, circuits, conductors, AC and DC, the dielectric strength of the acryl- inductance and capacitance, generators, ic, and some of the chemical bonds stress has weakened the dielec- motors, transformers, amplifiers, etc. Many that hold the acrylic molecules to- tric. The defect causes a localized questions with answers. gether are ripped apart. This strips concentration of the electric field, 390001- Basic Electricity ........ 15.95 away additional free electrons (a creating a "weak link" where the process called ionization). The breakdown process can begin. In- Basic Electronics newly-freed electrons are also ac- terestingly, even though we've US Bureau of Naval Personnel celerated by the electric field, injected a