PURPOSE: To set a separating distance at a tip to a necessary length and to obtain a desired potential inclination, by forming a sealed portion at one side of a light emitting bulb, connecting a base end portion of a pair of electrodes to a metal foil sealingly attached to the sealed portion, and widening an intermediate portion.
CONSTITUTION: A sealed portion 2 is formed to a one side of a light emitting bulb 1 and rare gas is introduced into it. A base end portion of an electrode 3 is welded to the center of a metal foil 5 and an intermediate portion 6 is widened. Therefore, a separating distance of the intermediate portion 6 formed is wider than the base end portion 4 and a tip portion 7. The light emitting tube 8 is accommodated in a outer tube 9 with one end thereof sealed and a lead wire 10 of the light emitting tube is connected to a lead wire 13 of the outer tube. With the arrangement, a separating distance of the intermediate portion 6 is made wider than the base end portion 4 even it the base end portion 4 is connected to the center of the metal foil 5. Then, the separating distance of the tip portion can be made to a necessary length, whereby a desired potential inclination can be obtained.
IWATO YASUHIRO
INUKAI SHINJI
MATSUURA ATSUSHI
