Abstract: A high-pressure discharge lamp includes an external tube, and two luminescent tubes which extend in the tube axis direction in such a manner that one tube twists with respect to the other or vice versa and which are close to each other at least at one end of each tube and are more separate in the middle of the tubes than the ends close to each other.

Abstract: In a discharge lamp having a discharge medium sealed in a discharge tube assembly including electrodes for producing a discharge, a nitride layer is formed on a surface of an envelope tube of the discharge tube assembly. The nitride layer is formed by substituting an oxygen component of an oxide constituting the tube wall of the envelope tube with nitrogen, and exhibits a continuous and smooth reduction in nitride content in the direction of depth. This chemically stable nitride layer prevents a reaction between the discharge medium and the tube wall material, and removal or injection of the discharge medium. In addition, since the nitride layer also exhibits a continuous change in thermal expansion coefficient in the direction of depth, the thermal stress is reduced, and cracking, peeling, removal, and the like do not occur.

Abstract: The invention provides a high-pressure discharge lamp incorporating an outer envelope storing a pair of electric terminals a plurality of arc tubes which are respectively stored in this outer envelope and electrically connected in parallel, and a plurality of ignition aids available for assisting operating of these arc tubes, where these ignition aids are provided for each of these arc tubes and contain potentials different from each other. In addition, the invention also provides a lighting system for operating the high-pressure discharge lamp.

Abstract: The invention provides a ceramic electric-discharge lamp having a pinch-sealer which is set to an end of an outer envelope and covered by a base having a pair of base pins projecting themselves into the base. The outer envelope is in vacuum, in which an arc tube composed of a square U-shaped tube is installed. Apertures of both ends of the square U-shaped illuminant are closed by ceramic discs each containing an electrode. Linear illuminant is formed in such regions where the radius of curvature of the square U-shaped arc tube greatly varies, in other words, between the curved portions.

Abstract: A high pressure sodium lamp including a light permeable arc tube and an electrode extending into the arc tube via a central aperture provided in the arc tube. The electrode is supported in the aperture by means of a glass solder sealing composition. Sodium amalgam is seated in the arc tube and condensed at a corner thereof. To prevent sodium amalgam condensed at the corner of the arc tube from contacting the glass solder filled in the central aperture of the arc tube, sodium amalgam including sodium of 10-30 (wt %) is sealed in the arc tube at a prescribed volume V (mm.sup.3) which substantially satisfies the following relationship: ##EQU1## where D (mm) is the diameter of the arc tube, d (mm) is the diameter of the central aperture, Vo (mm.sup.3) is the volume of the sodium amalgam sealed in the arc tube when the shortest distance between the sodium amalgam condensed at the corner and the glass solder filled in the central aperture is given by ##EQU2## and WL (W) is the lamp power.

Abstract: A high pressure sodium lamp includes a light permeable ceramic bulb wherein a pair of electrodes are oppositely arranged. One of the electrodes is inserted into one end of a metal tube, the other end of which is pinched. The center line average surface roughness of the inner surface of the metal tube is held below 2 .mu.m for preventing melted sodium-mercury amalgam condensed on the inner surface of the other end of the metal tube from moving along the inner surface of the metal tube by capillary action toward the one end thereof.