Abstract: A lamp in which a stable, long-term luminous operation can be accomplished is achieved by the fact that, in a mercury lamp of the short arc type in which a cathode and an anode located next to one another within an arc tube and in which both ends of the arc tube are provided with hermetically sealed portions, the cathode is installed on the tip of a rod-shaped component which extends from a respective one of the hermetically sealed portions, the cathode having a greater outer diameter than the rod-shaped component on which it is installed, and the rear end of the cathode tapering toward the respective hermetically sealed portion.

Abstract: A mercury lamp of the short arc type in which tantalum can absorb impurity gases to a sufficient degree even if the inside of the arc tube reaches a high temperature is achieved by providing an arc tube, within which mercury and an inert gas are encapsulated, with a pair of electrodes disposed opposite each other within the arc tube, each of the electrodes being supported by a respective terminal post, tantalum being provided on the terminal post of one of the electrodes, and by ensuring that both of the relationships (D2/D1)>1.3 and the relationship 0.2.ltoreq.(D2/D1).sup.2 /L.ltoreq.0.5 are satisfied at the same time, where D1 is an outer diameter of the terminal post in millimeters, D2 is an outer diameter of the electrode supported by the respective terminal post in millimeters, and L is a distance between a tip of the electrode on which the tantalum is provided and the tantalum on the terminal post of that electrode.

Abstract: A method and apparatus for manufacturing a bulb wherein a bead mount and a glass bulb are set in a recess in an upper surface of a heater arranged inside a hermetically sealed chamber, a first gas comprised of one component of a composition of a sealing gas in the glass bulb or an inert gas excluding the sealing gas is supplied to the chamber at a predetermined pressure after the chamber is evacuated, a second gas comprised of a remaining component of the sealing gas or all of the components thereof is sprayed in a space between the glass bulb and the bead mount at a pressure higher than that of the first gas to exhaust the first gas from the space within the glass bulb. The heater is energized after the substitution of the gas within the space of the bulb is performed, or while the gas substitution in the space is being performed, in order to heat and melt an edge portion of the bead mount and glass bulb to seal the glass bulb to the bead mount with the second gas sealed within the glass bulb.