gasontlading

Gasontlading, in physics and engineering, is the process whereby an electric field provides enough energy to ionize a gas, turning an insulating medium into a conductive plasma and allowing current to flow. Ionization occurs when energetic electrons from a nearby conductor collide with gas molecules, creating additional ions and electrons in an avalanche. The discharge behavior depends on pressure, gap distance, and gas composition.

Two common regimes characterize gas discharges. In the Townsend regime, at voltages below the breakdown threshold, the current is carried by a chain of ionization events, with little visible light. At higher voltages, a breakdown can occur, leading to spark or arc discharges. If the current is limited and the discharge is stable with visible glow, it is called glow discharge, producing characteristic light and used in devices such as neon tubes. Corona discharge is a weaker, non-uniform ionization around sharp conductors.

Gases used vary widely: air, neon, argon, krypton, mercury vapor in lamps, and insulating gases such as SF6 in high-voltage equipment. The choice affects breakdown voltage, color of emitted light, and stability of the discharge.

Applications include neon signs, gas-discharge tubes for surge protection, fluorescent and plasma-display panels, high-voltage switches, and older vacuum tubes. The study of gas discharge is a branch of plasma physics and has shaped electrical insulation and lighting technologies.