| 摘要 |
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. <IMAGE> |
