An analysis on transmission microwave frequency spectrum of cut-off probe

We investigated the formation mechanism of transmission microwave frequency (TMF) spectrum of cut-off probe using a simple circuit model to elucidate the physics behind the TMF spectrum. The result showed that the overall shape of the TMF spectrum of cut-off probe (N - shape spectrum) is well reproduced with our proposed circuit model and can be understood as the combined result of two different resonances caused by the elements between two probe tips (a sheath, a plasma, and a vacuum which is filled by the plasma). Furthermore, based on this simple modeling, a more precise method to find the plasma frequency by taking account with the e-n collision frequency and the pressure limitation of the cut-off probe application is established. (C) 2011 American Institute of Physics. [doi:10.1063/1.3634022]