Abstract: A discharge lamp includes an emitter other than thorium, which is added to a cathode in a luminous tube. Early depletion of the emitter due to excessive vaporization of the emitter from the cathode is prevented, while achieving stable lighting even at the start-up of the lighting. A main body part (31) of the cathode (3) is made from a high-melting-point metal material that contains no thorium, and a front end part (32) thereof is made from a high-melting-point metal material that contains an emitter (other than thorium). A sintered compact (34), which contains an emitter (other than thorium) at a concentration higher than the emitter contained in the front end part (32), is buried in a sealed space (33) that is formed within the main body part (31) and/or the front end part (32). The sintered compact (34) abuts against the front end part (32).

Abstract: A discharge lamp includes a cathode in a luminous tube, and an emitter, other than thorium, is added to the cathode. The emitter is prevented from being excessively vaporized from the cathode and depleted soon. Smooth lighting is enabled even at start-up. A main body part (31) of the cathode (3) is made from a metallic material having a high melting point and containing no thorium. A front end (32) is made from a metallic material having a high melting point and containing an emitter (excepting thorium). Inside a sealed space (33) formed in the main body part (31) and/or the front end part (32) is received a sintered compact (34) containing an emitter (excepting thorium) that is higher in concentration than the emitter contained in the front end part (32).

Abstract: A discharge lamp includes an emitter other than thorium, which is added to a cathode in a luminous tube. Early depletion of the emitter due to excessive vaporization of the emitter from the cathode is prevented, while achieving stable lighting even at the start-up of the lighting. A main body part (31) of the cathode (3) is made from a high-melting-point metal material that contains no thorium, and a front end part (32) thereof is made from a high-melting-point metal material that contains an emitter (other than thorium). A sintered compact (34), which contains an emitter (other than thorium) at a concentration higher than the emitter contained in the front end part (32), is buried in a sealed space (33) that is formed within the main body part (31) and/or the front end part (32). The sintered compact (34) abuts against the front end part (32).

Abstract: A discharge lamp includes a cathode in a luminous tube, and an emitter, other than thorium, is added to the cathode. The emitter is prevented from being excessively vaporized from the cathode and depleted soon. Smooth lighting is enabled even at start-up. A main body part (31) of the cathode (3) is made from a metallic material having a high melting point and containing no thorium. A front end (32) is made from a metallic material having a high melting point and containing an emitter (excepting thorium). Inside a sealed space (33) formed in the main body part (31) and/or the front end part (32) is received a sintered compact (34) containing an emitter (excepting thorium) that is higher in concentration than the emitter contained in the front end part (32).