Patent ID: 6956326

Claim:
A gas discharge tube encapsulating a gas within a hermetic envelope and generating discharge between anode and cathode parts disposed within said hermetic envelope, so as to emit predetermined light from a light exit window of said hermetic envelope to outside, said gas discharge tube comprising: a first discharge path restricting part, disposed in the middle of a discharge path between said anode and cathode parts, having a first aperture for narrowing said discharge path; a second discharge path restricting part, disposed in the middle of a discharge path between said first discharge path restricting part and said anode part, having a second aperture for narrowing said discharge path; and a first electrically insulating part disposed between said first and second discharge path restricting parts, wherein a periphery of said second discharge path limiting part is surrounded by an insulator including said first insulating part, said second discharge path restricting part has a peripheral edge facing outwardly and away from said discharge path, and said insulator including said first insulating part comprises an insulator portion, located further from said discharge path than the peripheral edge of said second discharge path restricting part, which circumnavigates the peripheral edge of said second discharge path restricting part.