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Sounds like a "sulphur" lamp from before 1994. They used a microwaveOr is it like those miracle stories in EET?
Robert H.
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http://www.physorg.com/news125238861.html
A Tic-Tac-sized lightbulb that gives off as much light as a streetlamp may
offer a peek at the ultra-efficient lighting of the future. The bulb,
developed by Luxim of Sunnyvale, California, uses plasma technology to
achieve its brightness.
The tiny bulb contains an argon gas in the middle, as well as a component
called a "puck." The bulb is partially embedded in a dielectric material.
When electrical energy is delivered to the puck, the puck acts like an
electrical lens. It heats up the argon to a temperature of 6000 degrees
Kelvin, and turns the gas into a plasma that gives off light.
The plasma, whose 6000-degree temperature is similar to that of the surface
of the sun, also emits a spectrum that looks very similar to the spectrum of
sunlight.
The plasma bulb uses 250 watts, and achieves around 140 lumens per watt,
making it very bright and highly efficient. By comparison, conventional
lightbulbs and high-end LEDs get around 15 and 70 lumens per watt,
respectively.
source to excite the sulphur bit (turned into a vapor) in a low
pressure argon atmosphere. This is a 1960's (discovery) lamp that had
a lot of problems containing and exciting the plasma.
http://www.thekrib.com/Lights/sulphur.html
"In this new light bulb, sulfur excited by microwaves emits a bright
white light. At the DOE's headquarters, a sulfur bulb at each end of
one 240-foot-long light pipe replaced 240 individual 175-watt
high-intensity lamps. One Tootsie-Pop-size lamp gives off the same
light as more than 250 standard 100 watt incandescent bulbs."
Downside was the cost of the excitation gear - a magnetron and large
wattage lamps they were making - the smallest was 1,000 watts and way
more light than any single source could use - so they resorted to
light pipes and optics to distribute the light and that was too costly
for most applications.