Patent ID: 7569993
Filing Date: 2009-08-04
Classification: H01J

Abstract:
1. A gas discharge tube wherein a gas is enclosed in a sealed envelope, and a light is emitted outward from a light emitting window of the sealed envelope by producing a discharge between an anode portion and cathode portion both disposed in the sealed envelope, comprising: a first discharge path limit portion, arranged in a midway of a discharge path between the anode portion and the cathode portion, and provided with a first opening for narrowing the discharge path, the first opening having an entrance area and an exit area; a second discharge path limit portion, arranged in a midway of the discharge path between the first discharge path limit portion and the anode portion, and provided with a second opening having a straight section for narrowing the discharge path a diameter of which is constant and which extends in a direction of an optical axis, and a spread section a diameter of which increases in size from an end of the straight section on the side of the cathode portion toward the first opening and which extends in the direction of the optical axis, the diameter of the exit area of the first opening being larger than the diameter of the straight section of the second opening.