Patent ID: 7122960

Claim:
Emission device for an ultra-high pressure mercury lamp which comprises: a short arc ultra-high pressure mercury lamp having a silica glass arc tube containing a pair of opposed electrodes that have tungsten as a main component and that are spaced apart a distance of at most 2 mm, and being filled with at least 0.15 mg/mm 3 of mercury, a rare gas and an amount of halogen of from 1×10 −6 μmole/mm 3 to 1×10 −2 μmole/mm 3 ; and an operating device, the operating device being adapted to shift the surface of a tip area of at least one of the electrodes into a molten state during lamp operation; wherein the operating device has a means for superimposing a high pulse on the alternating lamp current immediately after polarity inversion.