Abstract: A gas discharge tube which generates discharge between an anode 24 and a cathode 56 disposed within a sealed container 12 in which a gas is sealed, includes a cylindrical part 28 restricting the discharge path, the cylindrical part being disposed between the anode and the cathode and having a through hole 42 for narrowing the discharge path between the anode and the cathode, and a discharge shielding part 50 which is disposed so as to cover a surrounding of the part restricting the discharge path and is electrically insulated from the part restricting the discharge path, wherein the part restricting the discharge path has a cathode side end projecting by a predetermined projecting amount more than a surface on the cathode side of the discharge shielding part and an anode side end projecting into a space 62 on the side where the anode is positioned so that a high-density electron region is formed only in a part on the cathode side of the through hole of the part restricting the discharge path to reliably gener

Abstract: A gas discharge tube which generates discharge between an anode 24 and a cathode 56 disposed within a sealed container 12 in which a gas is sealed, includes a cylindrical part 28 restricting the discharge path, the cylindrical part being disposed between the anode and the cathode and having a through hole 42 for narrowing the discharge path between the anode and the cathode, and a discharge shielding part 50 which is disposed so as to cover a surrounding of the part restricting the discharge path and is electrically insulated from the part restricting the discharge path, wherein the part restricting the discharge path has a cathode side end projecting by a predetermined projecting amount more than a surface on the cathode side of the discharge shielding part and an anode side end projecting into a space 62 on the side where the anode is positioned so that a high-density electron region is formed only in a part on the cathode side of the through hole of the part restricting the discharge path to reliably gener

Abstract: In a gas discharge tube 1 of the present invention, a focusing electrode portion 14 and a discharge limiting portion 30 are electrically insulated, and the discharge limiting portion 30 comprises a discharge limiting opening 31 which opposes an arc ball shaping concave portion 16. Thus the formation of a discharge path from a cathode portion 20 to the concave portion 16 is ensured and a starting discharge can be reliably generated. Further, by means of the discharge limiting opening 31 which opposes the concave portion 16, an arc ball S can be continuously maintained in an appropriate shape even when a lamp is illuminated, and thus the arc ball S can be shaped with stability, thereby stabilizing the luminance and light quantity.

Abstract: In a gas discharge tube 1 of the present invention, a focusing electrode portion 14 and a discharge limiting portion 30 are electrically insulated, and the discharge limiting portion 30 comprises a discharge limiting opening 31 which opposes an arc ball shaping concave portion 16. Thus the formation of a discharge path from a cathode portion 20 to the concave portion 16 is ensured and a starting discharge can be reliably generated. Further, by means of the discharge limiting opening 31 which opposes the concave portion 16, an arc ball S can be continuously maintained in an appropriate shape even when a lamp is illuminated, and thus the arc ball S can be shaped with stability, thereby stabilizing the luminance and light quantity.