| 摘要 |
It is an object of the invention to provide a discharge tube in which the electrical insulating property between the discharge trigger wires is not deteriorated by the sputtering substance generated when discharge is conducted between the upper and the lower discharge electrode. There are provided sub-discharge trigger wires 50 at the center of the inner circumferential wall of the airtight cylinder 10 under the condition that the sub-discharge trigger wires 50 are electrically insulated from the upper and the lower discharge electrode. At the same time, there are provided discharge trigger wires 30a connected with the upper discharge electrode and discharge trigger wires 30b connected with the lower discharge electrode in the upper and the lower portion of the inner circumferential wall of the airtight cylinder 10 at which there is no possibility of adhesion of the sputtering substance 40 generated in the process of discharging conducted by the upper and the lower discharge electrode. A distance between the discharge trigger wires 30a, 30b is electrically reduced via the sub-discharge trigger wires 50. An initial discharge is stably generated at an early stage between the fore end portions of the discharge trigger wires 30a, 30b and the end portions of the sub-discharge trigger wires 50 located close to the discharge trigger wires 30a, 30b.
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