SHORT-ARC TYPE EXTRA HIGH-PRESSURE MERCURY LAMP

PROBLEM TO BE SOLVED : To provide a short-arc type extra high-pressure mercury lamp capable of generating always stable arc discharge by suppressing shape distortion of an electrode. SOLUTION : Of a structure in which a pair of electrodes are set opposed to each other with an interval of 2 mm or less in an arc tube made of quartz glass, and mercury by 0.15 mg/mm3 or more, rare gas, and halogen within the range of 1×10-6 to 1×10-2 μmol/mm3 are sealed in the arc tube, at least one of the pair of electrodes is constituted of a molten large diameter part formed by melting a tip of a coil wound around a shaft part and a coil part formed continuously and integrally fastened to a rear part of the molten large diameter part, in which, an end part at the root of the coil is rounded without any acute-angle parts.