PURPOSE: To reduce temperature rising more effectively with a simple structure while increasing a radiation area and giving a cooling effect to an X-ray shield by providing unevenness on the X-ray shield surface surrounding the skirt part of a bulb.
CONSTITUTION: A cooling fin 2 made of a metal is fixed to the periphery of the face part 1a of a bulb 1 with adhesive 3, further a transparent plate 4 is fixed onto said radiating fin 2 with adhesive 5, while a coolant 6 is sealed in the space between the face part 1a and the transparent plate 4. Also an X-ray shield 10 is arranged around the skirt part 1b of the bulb 1 in order to shield the X-rays generated by electrons colliding with the face part 1a. Said X-ray shield 10 is formed, for instance, into the serrated shape in order to give unevenness to its surface. Thereby, a cooling area is increased and accordingly the X-ray shield 10 is given a cooling effect in addition to the normal X-ray shielding effect so as to effectively conduct the heat in the face part 1a to the skirt part 1b for radiating it from the X-ray shield 10.
TSURUOKA MASAKAZU
ASANO TETSUO
