| 摘要 |
PROBLEM TO BE SOLVED: To effectively lower temperature of an electrode through improvement of heat radiation characteristics from the electrode, in a short-arc high pressure discharge lamp with increased input power for augmentation of irradiation light quantity, and, further, solve the problem of fluctuation of light irradiated even in case the high pressure discharge lamp is arranged vertically to be lit. SOLUTION: At least either electrode (20, 30) of the electrodes (20, 30) inside a luminous tube (11) is structured with a tapered part (21) at its body part (22) and its tip, and the tapered part (21) has grooves (25) formed with angle not more than 90 deg. against an electrode axis.
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