| 摘要 |
A particle charging apparatus (Boxer-Charger) is constructed by disposing electrode assemblies each consisting of corona discharge electrodes and excitation electrodes, in parallel to each other with a charging space interposed therebetween. An a.c. voltage is applied between the corona discharge electrodes in the respective assemblies to establish a main electric field in the charging space. When the a.c. main voltage has entered a half cycle of particular polarity such as, for example, negative polarity, an excitation high frequency voltage including fast-rising pulses having a pulse duration time of 1 ns-1 ms is applied between the corona discharge electrodes and the excitation electrodes in the assembly to generate a creeping streamer on the corona electrode surface and thereby form a two-dimensional plasma source. Only negative ions are drawn out from this ion source by the action of the main electric field, and these negative ions will travel through the charging space towards the assembly on the opposite side. In the next half cycle, the assembly on the opposite side emits negative ions in the opposite direction. Accordingly, dust particles passing through the charging space are charged as they are bombarded by the negative ions alternately from the opposite directions. If the phases of the main voltage and the excitation voltage are shifted by one-half cycle relative to each other, then charging by positive ions can be achieved.
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