High pressure discharge lamps.

摘要

In a high pressure sodium discharge lamp it has been found that rectification can be prevented by ensuring the amalgam does not make electrical contact with the electrode (17). To achieve this according to the invention a small shoulder member (11) is provided on the inside face of the end wall. Although the small height (1) effectively reduces the temperature differential between the bottom of the shoulder and the top (11a) the necessary differential to prevent the amalgam condensing out the top of the shoulder member is maintained by ensuring the width (W) of the shoulder member is a predetermined minimum thickness.