Microwave-Excited High-Density Plasma Column Sustained along Metal Rod at Negative Voltage

Abstract

We have studied the mechanism of a microwave-excited plasma column sustained along a graphite rod at a negative voltage. It was confirmed that an Ar plasma column is extended longer along the rod axis by increasing the negative voltage. Langmuir probe measurement showed that the electron density was higher than 1011 cm-3 at a gas pressure of 4.5 Pa with an incident microwave power of 200 W and a negative voltage of -240 V. Significantly localized electromagnetic fields were detected near the rod surface, indicating that surface waves propagated along the axis of the conductive (or nondielectric) graphite rod.