Comparison of Langmuir probe and hairpin methods to characterise microwave cool plasma

As plasma consists of particles, number of these particles refers to plasma density which is the main diagnostic problem, therefore different methods have been developed to measure the plasma density as well as its temperature. Langmuir probe underestimate the density measurements because the accuracy of an I-V curve depends on different factors such as instability in the plasma erosion of the probe tip due to sputtering by the microwave field. To improve the results we used a filtered Langmuir probe. To eliminate the difficulties of Langmuir probe we used hairpin method to determine the plasma density. This technique measures the electron density with a very high accuracy and reproducibility as compared to Langmuir probes. The hairpin probe is a U-shaped resonant structure which works based on measuring the plasma dielectric constant. The results from both methods have been compared in this paper.