Abstract: A high-intensity discharge lamp including an arc tube provided with a heat-resistant translucent discharge vessel forming a discharge space, an electrode structure, a discharge medium charged in the discharge vessel, the discharge medium being composed of a light-emitting metal including mercury and a starting gas, a support member electrically connected with the electrode structure of the arc tube and holding the arc tube and an outer bulb having the arc tube disposed therein along a tube axis and sealed with a support member at an end portion thereof. The electrode structure has an electrode shaft hermetically sealed at each of opposed end portions of the discharge vessel and having a tip portion disposed in the discharge vessel, a coiled electrode wound around the tip portion of the electrode shaft disposed in the discharge vessel, and a recessed portion or a protruding portion formed on the electrode shaft spaced from the coiled electrode.

Abstract: A metal halide lamp has an outer envelope (3, 23) of quartz glass which sounds a discharge vessel (2, 22) of quartz glass. The discharge vessel (2, 22) gas-tightly retains an ionizable fill which includes sodium. In order to avoid loss of sodium from the discharge vessel (2, 22) due to UV radiation impinging upon current supply wires (8, 9, 28, 29) extending from the discharge vessel (2, 22) within and into the outer envelope (3, 23), the quartz glass of the outer envelope is doped with materials absorbing UV radiation, preferably cerium aluminate and titanium oxide; the outer envelope is spaced from the discharge vessel by at most 5 mm, the sodium content in the ionizable fill is at most 0.7 mg.sup.3 of the discharge volume, and the space within the outer envelope is evacuated.

Abstract: An alkali metal vapor discharge lamp is operable in a pulsed mode. The vapor discharge lamp includes an inner envelope made of first ceramics and an outer envelope made of second ceramics for enclosing the inner envelope under a vacuum atmosphere or an innert atmosphere. The inner envelope contains cesium, mercury and a rare gas, the vapor pressure of which cesium is selected from 400 to 1000 Torr. The second ceramics of the outer envelope is selected to be alumina ceramics.

Abstract: In a metal vapor discharge lamp for operating it by high voltage generated in the actuation of a heat sensitive switch means in an outer bulb, a relatively low pressure of a sealed gas or mercury is sealed in the outer bulb to operate the heat sensitive switch means in the gas atmosphere to control the surge voltage to a desired degree whereby the discharge lamp is operated without failure and the insulation breakdown of a ballast and an operation circuit is prevented.

Abstract: A metal vapor discharge lamp including an arc tube including an outer bulb and having at least an oxide crystal incorporated in the outer bulb, with a starting aid equipped on the outer circumference of said arc tube; at least one end of said arc tube having a heat insulator to keep the end warm, and a rare gas enclosed at 100 Torr or above together with at least sodium and mercury in said arc tube.