Gas-discharge lamp

Typically, such lamps use a noble gas (argon, neon, krypton, and xenon) or a mixture of these gases.

Some include additional substances, such as mercury, sodium, and metal halides, which are vaporized during start-up to become part of the gas mixture.

One hundred years of research later led to lamps without electrodes which are instead energized by microwave or radio-frequency sources.

The lamp consisted of a Geissler tube that was excited by a battery-powered Ruhmkorff induction coil; an early transformer capable of converting DC currents of low voltage into rapid high-voltage pulses.

Initially the lamp generated white light by using a Geissler tube filled with carbon dioxide.

[14] Intended for use in the potentially explosive environment of mining, as well as oxygen-free environments like diving or for a heatless lamp for possible use in surgery, the lamp was actually developed both by Alphonse Dumas, an engineer at the iron mines of Saint-Priest and of Lac, near Privas, in the department of Ardèche, France, and by Dr Camille Benoît, a medical doctor in Privas.

[16] The lamps, cutting-edge technology in their time, gained fame after being described in several of Jules Verne's science-fiction novels.

[17] Each gas, depending on its atomic structure emits radiation of certain wavelengths, its emission spectrum, which determines the color of the light from the lamp.

In many types the electrodes consist of electrical filaments made of fine wire, which are heated by a separate current at startup, to get the arc started.

In this case the heat of the discharge is used to actuate the switch; the starter is contained in an opaque enclosure and the small light output is not used.

The ionized gas moves randomly between the two electrodes which produces a flickering effect, often marketed as suggestive of a candle flame (see image).

[19] High-pressure lamps have a discharge that takes place in gas under slightly less to greater than atmospheric pressure.

Applications include indoor lighting of high buildings, parking lots, shops, sport terrains.

A high-intensity discharge (HID) lamp is a type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube.

Particularly robust versions of this lamp, known as strobe lights, can produce long sequences of flashes, allowing for the stroboscopic examination of motion.