Effect of an AC-modulated cathode on particle trap in a dusty DC discharge

Summary form only given, as follows. A localized particle trap or dust cloud commonly observed in dusty plasmas is a basic and significant structure for understanding characteristics of dusty plasmas. It occurs around the plasma-sheath boundary resulting from balance among various forces exerted on particles. In general, characteristics of a particle trap such as its overall size, shape, trapping position, interparticle distance, etc are highly dependent on both operating and plasma parameters. In order to find a possible way to control dust particles inside the plasma, dc cathode voltage for plasma generation was superimposed with small ac voltage, and the effect of the ac-modulation on dust trap structure was investigated by comparing the aforementioned characterizing parameters with those of the dc case through measurement and numerical analysis. Results show that the ac modulation of the cathode voltage brings about expansion of dust cloud and shift of particle trap position depending on particle size, and it also possibly induces spatial separation of a collection of dust particles of different sizes. Control of the dust void structure such as void size by the ac modulation is suggested as well.