Short metal vapor ceramic lamp
View Patent ↗A high intensity arc discharge lamp having a short metal seal plug running hotter than typical of capillary seals, enables a lamp with a metal fill to achieve a vapor pressure higher than the one set by the cold spot temperature typically of a capillary seal lamp. Corrosive fill materials, such as halogens are excluded. Zinc may be used to in starting the lamp.
1. A high intensity discharge lamp comprising:
an envelope substantially formed of a ceramic material; the envelope having a wall defining an enclosed volume with an interior surface; the wall formed with at least one passage extending from the interior surface of the enclosed volume to an exterior side of the wall;
at least a first electrically conductive electrode extending into the enclosed volume and electrically coupled through a seal plug having a metal seal portion that is hermetically sealed in the passage to close the passage without the use of a frit;
a chemical fill located in the enclosed volume, the chemical fill consisting of sodium metal, thallium metal, indium metal and mercury metal; and
an inert gas in the enclosed envelope, the inert gas having a fill pressure greater than five kilopascals at 20 degrees Celsius.
2. The lamp of claim 1 , wherein the ceramic material is polycrystalline alumina.
3. The lamp of claim 2 wherein the metal seal portion is comprised of a first metal selected from tungsten and molybdenum and alloys thereof, and a second metal selected from chromium, titanium, vanadium and alloys thereof.
4. The lamp of claim 1 wherein the inert gas is xenon.
5. The lamp of claim 1 wherein the fill is 6.64 molar percent indium, 49.64 molar percent sodium, 38.06 molar percent mercury and 5.65 molar percent thallium.