Diagnostics in lamp research to evaluate HID-electrode and ballast performance

Electrodes in a high intensity discharge (HID) lamp play a major role in the successful operation of these light sources. On one hand a "good" electrode has to fulfil the fundamental task of supplying power to the discharge, on the other hand it has to survive the demanding conditions of the thermal and chemical environment in an HID lamp for many hours of operation. The performance of the electrodes during starting and continuous operation in an HID lamp is strongly dependent on the type of ballast used. Improper design of electrodes and ballasts can lead to life-limiting problems. The paper focuses on diagnostic efforts to shed some light on the complex electrode, plasma and ballast operation.