Xenon arc lamp Jyoti Sarita Mohanty 09-01-2016 What is Xenon arc - - PowerPoint PPT Presentation

Xenon arc lamp

INSTRUMENTAL TECHNIQUE PRESENTATION

Jyoti Sarita Mohanty 09-01-2016

What is Xenon arc lamp?

• Xenon arc lamp is a gas discharge lamp where electric power is converted into light

by an arc discharge in a xenon atmosphere at high pressure.

• It produces bright white light that closely resembles natural sunlight.
• Xenon has the highest overall conversion efficiency.
• used in movie projectors in theatres, in searchlights, and for specialized uses in

industry and research laboratories. Xenon arc lamps can be roughly divided into three categories:

• 1. Continuous-output xenon short-arc lamps
• 2. Continuous-output xenon long-arc lamps
• 3. Xenon flash lamps (which are usually considered separately)

• Carbon arc lamp was the first electric light invented by Humphry Davy in the early
• 1800s. This was the first widely-used and commercially successful form of electric

lamp.

• 1875 Pavel Yablochkov had developed the Yablochkov Candle which was the first

reliable carbon arc lamp and was used in Paris.

History of arc lamp

• 1870s-1890s Elihu Thomson and E.W. Rice Jr improved many parts of the arc light

system both in DC and AC power.

• Then xenon short-arc lamps were invented in the 1940s in Germany and introduced

in 1951 by Osram. First launched in the 2 kW size and now it is upto 15 kW.

Xenon arc lamp construction

• There is a fused quartz envelope with thoriated

tungsten electrodes. Fused quartz is the only economically feasible material currently available that can withstand the high pressure and high temp.

• the tungsten electrodes are welded to strips
• f pure molybdenum metal or Invar alloy, which

are then melted into the quartz to form the envelope seal.

• Because of the very high power levels involved,

large lamps are water-cooled, An O-ring seals

• ff the tube, so that the naked electrodes

do not contact the water.

• In order to achieve maximum efficiency, the xenon gas inside short-arc lamps is

maintained at an extremely high pressure — up to 30 atmospheres — which poses safety concerns, large xenon short-arc lamps are normally shipped in protective shields.

The mechanism of light generation

• In a pure xenon lamp, light is generated

within a tiny, pinpoint-sized cloud of plasma situated where the electron stream leaves the face of the cathode.

• The light generation volume is cone-shaped,

and the luminous intensity falls off exponentially moving from cathode to anode causing it to heat.

• The output of a pure xenon short-arc lamp offers

fairly continuous spectral power distribution and light intensity ranges from 20,000 to 500,000 cd/cm2.

• In xenon-mercury short-arc lamps, light is generated

in a pinpoint-sized cloud of plasma situated at the tip

• f each electrode.
• All xenon short-arc lamps generate substantial ultraviolet radiation and these readily

pass through the fused quartz lamp envelope. So some lamps have envelopes made

• ut of ultra-pure synthetic fused silica which allows them to emit useful light into the

vacuum UV region.

Spectral distribution of xenon arc lamp

• Xenon short-arc lamps come in two distinct varieties: (i)pure xenon,

which contains only xenon gas; and (ii) xenon-mercury, which contains xenon gas and a small amount of mercury metal.

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