High pressure discharge lamp and luminaire

摘要

A high-pressure discharge lamp which includes a translucent ceramic discharge vessel having a swollen portion defining a discharge space and a pair of cylindrical portions formed in and communicating with the swollen portion and extending from the swollen portion in the opposite directions with each other. The high-pressure discharge lamp also includes metal tubes each having a outer diameter D and fit with its one end on the cylindrical portion, a pair of fusible metal plugs each plugged in the outer end of the metal tube, the fusible metal plug sealing the discharge vessel by being fused to the inner surface of the metal tube for a specified height T from the outer end of the metal plug, a pair of electrode systems each supported its one end to the fusible metal plug and facing the interior of swollen portion with its other end, and ionizing filling filled in the discharge vessel The ratio T/D of the height T concerning the fusible metal plug and the diameter D satisfies the following equation 0.40<=T/D&LE;0.95.