| 摘要 |
PROBLEM TO BE SOLVED: To obtain a reliable operating current by means of small radioactivity by a method wherein an ion source is installed inside a thin chamber whose internal particle travel distance is shorter than a specific value and the ion source is selected from a kind whose initial emission energy level is lower than a specific voltage. SOLUTION: A smoke detector 20 in which a chamber 10 is built is provided with a housing 22, it is opened in such a way that a combustion product such as a smoke particle substance can be taken into and out, it is adjacent to a peripheral region in such a way that a particle substance and smoke can enter an active chamber. A control circuit 24 is supported by a printed-wiring board 26 inside the housing 22. In addition, the smoke detector 20 is connected to an alarm system. Then, the chamber 10 is formed to be a thin shape whose internal particle travel distance is shorter than 2.5 cm, an ion source is installed inside the chamber 10, and the ion source is selected from a kind whose initial emission energy level is lower than 4 MeV. Then, the ion source discharges particles inside the chamber to a route corresponding to the internal particle travel distance.
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