High pressure sodium lamp containing barium getter

摘要

A high pressure sodium lamp comprises an elongated arc tube within an evacuated outer jacket, the arc tube containing a fill including sodium and mercury. A barium getter film is disposed on the inner jacket wall at one end thereof. The film is longitudinally spaced more than 1 cm away from the end of the arc tube in order to reduce photoelectron emission from the barium which can cause sodium migration from the arc tube.