Discharge tube

A discharge tube comprising:

• a cylindrical envelope made of an insulating substance;
• discharge gas enclosed in said envelope;
• a pair of discharge electrodes disposed in an opposing relationship to each other at the opposite ends of said envelope, said discharge electrodes being formed as parallel plate electrodes wherein faces thereof facing the inside of said envelope extend flat and in parallel to each other;
• a pair of conductive layers formed on said envelope in an opposing relationship to and electrically connected to said discharge electrodes, one of said conductive layers being opposed at least part thereof with the other conductive layer with a portion of said envelope interposed therebetween;
• and
• a sputtering preventing member disposed on one of said discharge electrodes which serves as an anode in such a manner as to cover over a central portion of a surface of the one discharge electrode opposing to the other discharge electrode.

A discharge tube comprising:

• a cylindrical envelope made of an insulating substance;
• discharge gas enclosed in said envelope;
• a pair of discharge electrodes disposed in an opposing relationship to each other at the opposite ends of said envelope, said discharge electrodes being formed as parallel plate electrodes wherein faces thereof facing the inside of said envelope extend flat and in parallel to each other;
• a pair of conductive layers formed on said envelope in an opposing relationship to and electrically connected to said discharge electrodes, one of said conductive layers being opposed at least part thereof with the other conductive layer with a portion of said envelope interposed therebetween;
• and
• an external creeping discharge preventing member made of an insulating substance and disposed such that it covers over said conductive layers.

A discharge tube, comprising:

• a cylindrical envelope made of an insulating substance;
• discharge gas enclosed in said envelope;
• first and second discharge electrodes disposed in an opposing relationship to each other at opposite ends of said envelope;
• and
• first and second conductive layers corresponding to said first and second discharge electrodes, respectively, formed on an outer end face of said envelope,
• wherein a distance between the first and second conductive layers is less than a distance between the first and second discharge electrodes, and
• wherein said conductive layers are electrically connected to the respective corresponding discharge electrodes.