Comparison between experimental Langmuir probes and three species one-dimensional kinetic simulations

The biasing of Langmuir probes to obtain the appropriate measurements in weakly ionized plasmas is addressed in this work. The experimental results show discrepancies when this measurement method is employed with sweep signals of different symmetries or frequencies. This means that the method provides signal dependent plasma parameters, which hinder its diagnosis. In this work, a three species one-dimensional kinetic model is applied with a sweep electric field to simulate the dynamics of a weakly ionized plasma close to a Langmuir probe. With the same symmetries and frequencies for the sweep signal in both the experimental and numerical problems, a qualitative similar behaviour is found. The response of the three species plasma due to changes of the electric field is analysed by means of a three species kinetic collisional model. The effect of constant averaged or energy dependent characteristic collision frequencies is studied. These numerical results are useful to provide a first explanation of the dis...