Detection and analysis of plasma species using a compact mass spectrometer

Abstract

The concentration of the ion species in plasma is an important parameter in applications using plasma discharges such as thin film deposition, ion implantation and other plasma processes. To determine the ionic concentration in plasma a mass spectrometer is needed. However, commercial mass spectrometers are often very large, complex and very expensive, making them unsuitable for most researchers. Thus, a compact, simple and relatively cheap mass spectrometer is greatly needed.
Recently, Sanchez and Ramos constructed a compact mass spectrometer optimized to extract H⁻ ions from magnetized sheet plasma of hydrogen gas. This paper aims to detect light ions using the same design of the mass analyzer used for H⁻ extraction in a plasma discharge. In this case, however, the ions are extracted from side-on measurements unlike in a previous study where the beam was directed straight into the mass analyzer. The parameters in the peripheral regions of the arc plasma were obtained using the mass analyzer. The H⁻ current is compared to the amount of current extracted. The characteristics of H⁻ current are then correlated to the H⁻ density. Results obtained with the extraction of hydrogen ions and electrons are indicative of the sensitivity of the mass spectrometer system.