ABSTRACT
INTRODUCTION UHP lamps are the standard light source for projection applications [ 1]. Essential characteristics of UHP lamps are a high mercury pressure above 200 bar for a good spectrum and high burning voltage, and the implementation of a chemical cycle which keeps the wall clear over thousands of hours lamp life. The small display sizes require very short arcs in the order of lmm. The electrode front has to deal with current densities of 10kAcm-2 and heat loads of 100kWcm-2. Obviously it is a major task of UHP electrode design to handle this heat load and realize an electrode temperature low enough to reduce electrode burn-back to a minimum so that the required short arc length is maintained.
