In-situ measurement of electrode work function in high pressure lamps

Summary form only given. High electrode temperatures are detrimental for maintenance and lifetime behaviour of high pressure discharge lamps but a certain minimum temperature is necessary because the electrode has to deliver the lamp current. This temperature is strongly correlated to the work function. Existing work function measurements by thermoemission or contact potential methods are "vacuum" methods and cannot be used in operating high pressure lamps. An in-situ method is important because determining factors like electrical fields and temperature gradients of the electrodes are determined by the presence of the discharge. Here, the authors describe measurements of work functions which can lead to an improved understanding of the physical processes in the electrode region and are of great interest for discharge lamp developers.