High-pressure sodium lamp

摘要

A high-pressure sodium lamp in which the inner diameter of an arc envelope is largest at the midpoint between the ends thereof and the inner and outer diameters thereof in the vicinity of the ends at which are air-tightly fitted electrodes and their associated parts are reduced gradually relative to the inner diameter of the midpoint thereof. When the arc envelope is turned on, the following conditions are satisfied: Te>/=0.85 Tc and 1020 DEG C.