Automated plasma parameter measuring system using electrical probe

Abstract

In order to obtain the value of plasma parameters, including the plasma potential, the electron temperature, and the plasma density, the use of electrical probes is one of the techniques which can be accomplished by measuring current as a function of voltage. In this work, a computer controlled bipolar power supply was setup as a voltage source for the probe current measurement. The adjustable potential of the source was supplied to the probe so as to acquire adequate current information which corresponds with each region in I-V characteristics. The measured I-V data were recorded and analyzed by an automated algorithm. In the algorithm, the I-V data were partitioned into three voltage intervals by using the first and second derivatives of the current signal. The characteristic of the first derivative curve was utilized to determine the ion and electron saturation regions, while the interval between the maximum and minimum of the second derivation could be defined as the transition region. In the analysis of actual experimentally acquired data obtained from different plasma discharges, the algorithm performed well and also yielded plasma parameters with good agreement to the results obtained by usual manual calculation.