| 摘要 |
A high pressure sodium vapor lamp having an elongated light-transmitting refractory arc tube with closure members sealing each end of the arc tube. An elongated hollow refractory metal member of predetermined length and surface area projects from the arc tube and is sealed through one of the closure members. The interior of the hollow metal member opens into the interior of the arc tube and the projecting end of the hollow metal member is sealed. During the operation of the lamp, the hollow metal member acts as a condensing repository for excess discharge sustaining filling which is not vaporized since the coolest spot of the hollow metal member is at a temperature less than the arc tube. The hollow metal member is provided on the outer surface with a radiation-emissive and electrical-insulating means, and a resistive-heater member is affixed to the exterior of the hollow metal member and in thermal contact with the radiation-emissive and electrical-insulating means. The resistive-heater member generates a predetermined power dissipation when carrying the normal operating current of the lamp to provide a heating effect for the metal member. Voltage rises in the lamp are normally encountered during prolonged operation and typically cause the lamp current to decrease, reducing the heating provided by the resistive-heater member which at least in part compensates for the tendency for increased voltage to be developed across the arc tube.
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