An apparatus includes a shaft, the shaft including a plurality of stepped sections along the length of the shaft. The apparatus further includes a plurality of electrodes disposed along the length of the shaft, each electrode characterized by a geometric aspect ratio of the length of the electrode to the outer diameter of the electrode. Each electrode is located at a different stepped section of the plurality of stepped sections of the shaft and includes a set of leads. Each lead of the set of leads is configured to attain an electrical voltage potential of at least about 1 kV. The geometric aspect ratio of at least one electrode of the plurality of electrodes is in the range between about 3 and about 20.