A novel experimental method for in situ diagnostics of electrode workfunctions in high-pressure gas discharge lamps during operation

In this work a new diagnostic method is presented, which allows the in situ detection of the electrode workfunction of high-intensity discharge (HID) lamps during normal lamp operation. With this novel tool it is possible to investigate the electrode emission behaviour of HID lamps during operation, which is influenced, for example, by high electric fields at the electrode surface. After verification of the experimental method using a specially designed test system, the new method is applied to HID lamps, in which different are attachment modes, due to different emitter concepts, are used. This new method is based on the photoelectric effect at hot metal surfaces. With the well known theoretical description of this process, including the presence of electric fields, the short-time electric signals induced by pulse laser irradiation can be interpreted and the workfunction can be determined. Effects causing experimental uncertainties are investigated and can be quantified. Appropriate corrections are possible.