Discharge lamp of the short arc type and a light source device having the discharge lamp of the short arc type

A discharge lamp of the short arc type, comprising:

• a bulb with an arc tube and sealing tubes continuously extending from opposite sides of the arc tube, a discharge gas and a pair of opposed electrodes being located inside of the arc tube, a lead pin supporting each of the electrodes and protruding from an outer end of a respective one of the sealing tubes and being affixed to a graded glass in the sealing tube;
• and
• a cooling fin that surrounds an outer surface of one of said sealing tubes, the cooling fin comprising a pair of plate-shaped bodies each of which has a curved portion placed so as to contact the outer surface of said one of said sealing tubes and a strip-shaped portion extending radially outward from each of opposite edges of the curved portion,
• wherein the strip-shaped portions of the plate-shaped bodies positionally overlap,
• wherein cooling openings are formed on the strip-shaped portion of only one of the plate-shaped bodies in such a way that air passing through said cooling openings strikes against the strip-shaped portion of the other one of the plate-shaped bodies, and
• wherein the ratio of the surface area of the plate-shaped body which is not provided with openings to the total combined aperture areas of all of the cooling air openings is within a range of 20% to 30%.