Effect of microwave field on the Langmuir probe characteristics in measurements of high-density plasmas

摘要

How the Langmuir probe V-I characteristics are distorted by the presence of microwave field in theplasma is studied computationally using a fluid model. The effect of microwave field is simulated asan oscillating potential difference between the plasma and the probe surface The results ofcomputation show that, when the electron density (ne) is low (electron plasma frequency ωpe ω), the V-I curve shows a significant distortion around a particular DC bias potential, so thatthe second derivative of the V-I curve shows a dip around that potential. The position of the dip depends on ne and moves towards shallower bias potentials as n ne increases. The results of computation give an explanation for the discrepancy between recent Thomson-scattering and probe measurements of electron energy distribution in a surface wave plasma.