Abstract: In a metal halide lamp of the sodium-scandium-thorium iodide type utilizing tungsten electrodes without emission mix, lumen depreciation during life results primarily from blackening of the arc tube wall by electrode sputtering during the glow-to-arc transition phase of lamp start-up. The glow-to-arc transition is speeded up by a lower glow-to-arc transition voltage which is achieved by using electrodes comprising an open tungsten wire coil on a tungsten shank, the coil comprising two layers of a composite wire made by open-winding a 2 mil overwind on a 4 mil core and then close-winding two layers of the composite wire on the shank. This decreases sputtering at starting and improves lamp maintenance.

Abstract: A jacketed high pressure metal vapor discharge lamp comprising an arc tube having main electrodes at opposite ends and a starter electrode, has a resistor and a diode in series bridged across the main electrodes which are connected across a peaked lead ballast in operation. A second resistor connects the starting electrode to the remote main electrode. The circuit lowers the minimum open circuit voltage required from the ballast for reliable starting.

Abstract: A titania-silicate glass zone or layer is formed at the surface in fused silica by first applying a thick opaque polycrystalline titania powder coating to the silica and then fusing the coating into the silica at a high temperature. Such a zone reduces the ultraviolet transmission of the silica and also lowers its sodium ion conductivity. The zone may usefully be formed on the fused silica arc tubes of metal halide lamps in order to inhibit sodium loss and on other discharge lamps required to be ozone free.

Abstract: New sealant compositions for sealing end closures or inleads in ceramic envelopes are based on the system Dy.sub.2 O.sub.3 -Al.sub.2 O.sub.3 -SiO.sub.2. These compositions will withstand metal halides used as arc materials up to temperatures exceeding 1200.degree. C, and make possible more efficient lamps of improved color rendition.

Abstract: A coating of zirconium is bonded to niobium by applying to the niobium a paint of Mo and Zr powder which is fired above 1520.degree. C but below the zirconium-niobium liquidus temperature of 1740.degree. C. Such coating is used in making an improved seal by juxtaposing the metal body to the ceramic body, applying a powdered alumina sealing glass or frit and firing to the melting temperature of the frit.

Abstract: A high pressure alkali metal vapor lamp envelope of alumina ceramic has an end closure which includes an externally projecting thin-walled metal tube serving as in inlead and as a reservoir for excess alkali metal. An electrode is mounted on a tungsten shank which projects into the metal tube and is locked in place by crimping the tube about it externally of the envelope. The crimping leaves restricted channels which allow passage of the alkali in vapor form but prevent its movement as a liquid.

Abstract: Jacketed high pressure sodium vapor lamps of conventional construction operated on sonic frequency pulses with short duty cycles in order to raise the color temperature produce excessive acoustic noise. The noise level is reduced by using non-magnetostrictive material for the inleads extending from the base into the outer envelope and including the portions embedded in the press of the stem, and for the frame parts that support the arc tube within the outer envelope.

Abstract: A high pressure sodium vapor lamp arc tube of alumina ceramic has end closures one of which includes an externally projecting tube of niobium or tantalum serving as inlead and having a portion extending into the inside of the arc tube. A tungsten electrode shank is welded into the end of the niobium tube but the seal at the weld may not be fully hermetic. To assure a fully hermetic seal, a mixture of yttrium and zirconium which has a lower melting point than pure yttrium is included in the niobium tube.

Abstract: High pressure sodium vapor lamps operated on sonic frequency pulses with short duty cycle in order to raise the color temperature are subject to arc instability near the electrodes and to overheating of the end closures, particularly that at the anode end when unidirectional pulsing is used. Stability and long life is achieved and overheating is prevented by using electrodes of cross-sectional area from 0.3 to 0.4 times the envelope cross section and lengthening the distance from closure to electrode tip so that the arc gap is less than 80% of the gas column length.

Abstract: A graded alumina silicate glass layer or zone is formed at the surface of fused silica by first applying a polycrystalline coating of aluminum oxide to the silica and then fusing the coating into the silica at a high temperature. Such a zone on the outside of the fused silica arc tube of a metal halide lamp containing sodium is particularly effective to inhibit sodium loss by diffusion through the tube walls.

Abstract: The inner arc tube of some jacketed discharge lamps transmits ultraviolet radiation which is normally intercepted by the glass outer envelope. To prevent harmful release of such radiation in the event the outer envelope should be shattered, a mechanical disconnect is provided in the interenvelope space comprising separable conductors which are part of the arc tube supporting frame and which are maintained in engagement by the outer envelope. Upon fracture of the outer envelope, spring pressure forces the conductors apart whereupon the circuit is opened and the arc tube is disabled.

Abstract: In a high pressure alkali metal vapor lamp arc tube having a sealed off metal exhaust tube projecting through an end closure, the tip of the exhaust tube is the cold spot where excess alkali metal condenses. A fine mesh screen friction-retained in the exhaust tube prevents passage of liquid droplets; any alkali metal impinging on the screen is slowly revaporized and condenses at the tip due to the higher temperature at the screen.

Abstract: A metal vapor arc lamp comprises an alumina ceramic arc tube having an end closed by an apertured ceramic plug sealed by sealing frit. A metal lead wire extending through the aperture is also sealed therein by sealing frit and supports an electrode within the arc tube. A cross wire attached to the inlead immediately above the plug forms a wick equalizing the distribution of sealing frit between the plug seal and the inlead seal and also serves as a hanger for supporting the plug and electrode assembly in the arc tube during sealing.

Abstract: A high pressure sodium vapor lamp utilizing an alumina arc tube within an outer envelope has a getter structure comprising a niobium portion operating in a high temperature range and a titanium portion operating in a lower temperature range. The niobium portion includes a connection extending from a niobium end closure structure of the arc tube to the titanium portion. The titanium portion may form one of the lead supports within the outer envelope or it may merely extend along one of the lead supports. This eliminates the need for the conventional barium getter flash which tends to coat the outer envelope and absorb light.

Abstract: A long life tungsten halogen lamp comprising a fused silica envelope containing a coiled tungsten filament connected across inleads sealed therein which include inner portions of molybdenum wire. The molybdenum wire has been treated to increase its ductility and reduce the concentration of impurities at the surface. The fill gas at a room temperature total pressure of at least 2,000 torr comprises nitrogen, an inert gas and a bromine-bearing component which provides from 1.6 .times. 10.sup.-.sup.8 to 8.0 .times. 10.sup.-.sup.8 gram atoms of bromine per cubic centimeter of envelope volume.

Abstract: A long life tungsten halogen lamp comprising a fused silica envelope containing a coiled tungsten filament connected across inleads sealed therein which include inner portions of molybdenum wire. The molybdenum wire has been treated to increase its ductility and reduce the concentration of impurities at the surface. The fill gas at a room temperature total pressure of at least 2,000 torr comprises nitrogen, an inert gas and an iodine-bearing component which provides from 3.1 .times. 10.sup..sup.-7 to 9.6 .times. 10.sup..sup.-7 gram atoms of iodine per cubic centimeter of envelope volume.

Abstract: The inner arc tube of some jacketed discharge lamps transmits ultraviolet radiation which is normally absorbed without harm by the glass outer envelope but may be released should the outer envelope be broken off. This is prevented by a fuse heater and shunting thermal switch connected in series with the arc tube and located within the outer envelope. Should the outer envelope be broken, air cools the switch so that it opens. Current flow through the heater now raises its temperature and causes it to oxidize, thereby opening the circuit and disabling the lamp.

Abstract: The adherence of an optically reflective coating of refractory metal oxide particles such as ZrO.sub.2 or Al.sub.2 O.sub.3 on a fused silica discharge tube surface is improved severalfold by an adhesion layer consisting of colloidal aluminum oxide and boric oxide powders. The adhesion layer may be first applied and dried, the refractory metal oxide coating then applied, and the quartz tube then heated to a temperature greater than 460.degree. C., the melting point of boric oxide. The refractory metal oxide particles may also be applied admixed with the colloidal aluminum oxide and the boric oxide. The improved coating strength permits the use of a thicker layer of refractory metal oxide for higher optical and thermal reflection.

Abstract: In a discharge lamp where the arc tube has main electrodes and a starter electrode, there is provided a voltage doubling circuit comprising a diode and a capacitor connected in series across the input terminals. The circuit is poled to generate a positive potential at the junction of diode and capacitor which is coupled through a resistor to the starter electrode. Voltage doubling may be provided across the gap from starter to adjacent main electrode or from starter to remote main electrode to improve starting. Where the arc tube contains sodium, the positive potential may also be applied to the arc tube frame to reduce sodium loss by electrolysis.

Abstract: A high pressure sodium vapor lamp utilizing an alumina ceramic arc tube within an outer glass envelope is provided with a bi-metal switch which short circuits the arc tube at starting. Current flow through the switch causes it to heat up and open the short circuit, producing a voltage pulse which starts the lamp. The bi-metal is fastened to a pin conductor extending from the metal exhaust tube of the arc tube to the frame. The pin conductor, which receives heat by conduction from the exhaust tube and is also heated by lamp current flow, transmits sufficient heat to the bi-metal to maintain it deflected during normal operation.