Plasma globe
A plasma lamp is a physical toy with dielectric barrier discharge, which was popular in the 1980s. However, it was invented in the year 1892 by Nikola Tesla and was originally used for the investigation of plasma. Were made known plasma lamps by Bill Parker and the Museum Exploratorium as well ( the " header " ) had by the German science program header, which until October 2003, a plasma ball as a prize. Tesla called his invention the " noble gas discharge tube " ( " Inert Gas Discharge Tube "). Plasma lamps are also called plasma globe, plasma ball or plasma spheres. They are available in different shapes, for example, in a cylindrical shape.
Function
Although numerous variations exist, the principle remains the same. Plasma lamp is typically a transparent glass sphere, which is filled with a mixture of argon, neon, and nitrogen at low pressure. It is powered by a high-frequency alternating voltage of about 20 kHz and a few kilovolts, is generated in the base of the lamp by a transformer in combination with an electronic oscillator circuit. A small ball in the center serves as an electrode. The counter electrode forms the environment connected to the electricity grid.
When switching, charge carriers (electrons and ions), which are available by photoemission or ionizing radiation in the gas accelerates in the radially directed pitch. The lighter electrons get fast enough energy that they generate more charge carrier pairs by impact ionization. By collisional excitation and recombination creates the characteristic of the filling gas lights, see the glow discharge.
The constriction of the discharge on filaments ( from Latin Filum " thread, string, fiber" ) based on the following instability: Different positive ion space charge results in the appropriate concentration of the electrons, and thus the current density and the impact ionization, which increases the initial differences. The filaments heat up slightly and rise through convection. The glass sphere ensures through its up-and trans-shipment in time with the AC voltage ( see capacitor ) for both a limitation of the current as well as a distribution of current over the surface - would the ball is electrically conductive, the total current would focus on only one filament without limitation would cause arcing.
Both the glass and in the ambient air of the current occurs as the dielectric displacement current. Lead Conductive objects near or on the ball and focus this current, if I create, for example, his hand on the glass, so the discharge is from the contact surfaces starting stronger. Electronic devices such as touchpads in laptops, portable music players, radio receivers and similar devices may be disturbed in the vicinity of the lamp in their function. LED and gas discharge lamps such as fluorescent tubes and neon lamps can be stimulated to emit light. The glass should be UV resistant, otherwise the radiation damages the eye and generates ozone in the ambient air.
Variants
There are also so-called plasma discs ( see also Planon ), in which not a glass ball, but a flat surface provided with a phosphor on a flat glass is clearly visible flashes. You can see this example in the Star Trek movies and television series in the alcove of the Borg ( greenish glowing plasma disc on the Borg drone ).
Another variant is the so-called plasma tube. Here, the light is generated in a cylindrical body.
The world 's largest plasma ball with a diameter of one meter is at the Swiss Science Center Technorama in Winterthur, Switzerland.