SELF-SIMILAR SHEATH EXPANSION FROM A SEGMENTED PLANAR ELECTRODE

The expansion of the pulsed plasma sheath away from a segmented planar electrode is studied using a collisionless particle-in-cell simulatio n. One segment of the electrode is biased negatively, while the other is fixed at ground potential. Cases where the grounded and biased segm ents are semi-infinite and where the width of the grounded segment is equal to the ion-matrix sheath width are considered. For the case of t wo half-planes, one grounded and one biased, it is found that the expa nding sheath sweeps up ions from above the grounded segment and accele rates them to the biased segment, forming an are of high ion density e ncircling a void region at the junction between the segments. Further, for this case sheath expansion is found to be self-similar as the pro blem lacks any length scale excepting the sheath width. (C) 1996 Ameri can Institute of Physics.