Hid sodium lamp which incorporates a high pressure of xenon and a trigger starting electrode

摘要

High-intensity-discharge sodium lamp incorporates as a starting gas xenon at a pressure between 50 and 300 torrs, in order to improve the lamp efficiency and the spectral power distribution of the discharge. To facilitate lamp starting on a conventional pulse-type starting circuit, a trigger electrode is wrapped about the exterior of the arc tube proximate one of the lamp electrodes, with the potential applied to the trigger electrode during lamp starting being the same as that which is applied to the other or more remote lamp electrode. The starting pulse applied between the trigger electrode and the proximate lamp electrode initiates the lamp discharge. The trigger electrode also extends along the outer surface of the arc tube contiguous therewith toward the other electrode and the discharge, once initiated, progresses toward the other electrode. If the arc tube is pervious to the migration of sodium ions therethrough under the influence of an electric field during the normal lamp operation, the trigger electrode is effectively removed from the circuit by a switch or a high impedance to prevent such sodium ion migration.