A high pressure sodium lamp of the invention is provided with a discharge vessel (20) which is enclosed with intervening space (1) by an outer bulb (10), which space contains a gas-fill with at least 70 mol. % nitrogen gas. Electrodes (30a, 30b) are positioned in the discharge vessel (20) and are each connected to a current supply conductor (40a, 40b) which issues from the discharge vessel (20) at a respective end (21a, 21b) thereof. The discharge vessel (20) has between the electrodes (30a, 30b) a central portion (22) with length L and volume V. The discharge vessel (20) contains an amalgam containing a weight mHg of mercury and a weight mNa of sodium, whereby the following relations are fulfilled: and in which mHg and mNa are expressed in mg, and L and V are expressed in cm and cm, respectively.; This allows for a stable operation despite temperature fluctuations in the environment, while breakdown in the outer bulb (10) and damage caused by corrosion of current supply connectors (40a, 40b) is prevented.
|Patent number||EP19930200664, US 55|
|Publication status||Published - 1996|