Plasma globe

A plasma globe or plasma lamp (also called plasma ball, dome, sphere, tube or orb, depending on shape) is (usually) a clear glass sphere filled with a mixture of various noble gases with a high-voltage electrode in the center of the sphere.

Plasma filaments extend from the inner electrode to the outer glass insulator, giving the appearance of multiple constant beams of colored light (see corona discharge and electric glow discharge). Plasma globes were most popular as novelty items in the 1980s.

The plasma lamp was invented by Nikola Tesla after his experimentation with high-frequency currents in an evacuated glass tube for the purpose of studying high voltage phenomena, but the modern versions were known to be first designed by Bill Parker. Tesla called this invention an inert gas discharge tube.

Although many variations exist, a plasma lamp is usually a clear glass sphere filled with a mixture of various gases (most commonly neon, sometimes with other noble gases such as argon, xenon and krypton) at nearly atmospheric pressure. They are driven by high-frequency alternating current energy at approximately 35 kHz, 2–5 kV. This energy comes from a lower-voltage DC power supply usually connected to mains power, and flows through a high-voltage transformer combined with a high-frequency electronic oscillator circuit which together output a high frequency and high voltage AC to the electrode. Therefore, the circuitry inside the electrode can be considered as a specialized power inverter. The high-frequency high-voltage power, or radio frequency energy, is transmitted into the gas within the globe through an electrode at its center. A much smaller hollow glass orb can also serve as an electrode when it is filled with metal wool or a conducting fluid that is in communication with the transformer output. In this case, the radio-frequency energy is admitted into the larger space by capacitive coupling right through the glass. Plasma filaments extend from the inner electrode to the outer glass insulator, giving the appearance of moving tendrils of colored light within the volume of the globe (see corona discharge and electric glow discharge).

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