Analysis of the uncertainty in the measurement of electron densities in plasmas using the wave cutoff method

We have analysed the uncertainty of a measured electron density using a wave cutoff probe and compared it with that obtained using a double Langmuir probe and plasma oscillation probe. The wave cutoff probe gives an electron density from a measured plasma frequency, using a network analyser and radiating and detecting antennae. It can also measure the spatial distribution of the electron density. The cutoff method is free of many difficulties often encountered with Langmuir probes, such as thin film deposition and plasma potential fluctuation, and the uncertainty of the cutoff probe is not affected by the complex plasma environment. Here, the measurement technique is theoretically analysed and experimentally demonstrated in density measurements of an inductively coupled radio frequency plasma, and a comparison with the double probe and a plasma oscillation method with uncertainty analysis is also made.