LOW POWER HIGH VOLTAGE DISCHARGE LAMP AND METHOD OF OPERATING THE LAMP

PURPOSE: To extremely shorten a time for starting by specifying various requirements. CONSTITUTION: The starting current of a lamp 1 is controlled to be 5 to 10 times the rated current value, a discharge container 2 is forced to include at least halide of sodium and scandium or halide of rare earth metal of sodium and the mass of the container 2 is set within a range from 0.002 to 0.1g/W per output W watt of the lamp 1. Furthermore, the container 2 including xenon gas of sealing pressure 3 bar as a sealed gas at least at a normal temperature is provided with means for transmitting visible light beam by either partially reflecting or absorbing invisible light beam. The shaft part of an electrode 4 is 0.3mm in its maximum diameter, and mutually opposing parts of the electrode 4 are roundish. At least one factor out of 4 factors is combined, a period of time for reaching 90% of light flux is reduced from about 30 seconds to about 1 second so that the time for starting can be saved remarkably.