Process control of a plasma treatment of wool by plasma diagnostics

Abstract

Wool was treated in a large-volume microwave plasma source SLAN II [D. Korzec, F. Werner, R. Winter, J. Engemann, Scaling of microwave slot antenna (SLAN): a concept for efficient plasma generation. Plasma Sources Sci. Technol. 5 (1996) 216–234] to improve the felting tendency. To control this plasma process, the applicability of three plasma diagnostic methods, optical emission spectroscopy (OES), double Langmuir probe measurements (DLP) and mass spectrometry (MS), was investigated. The plasma is composed of a variety of species like electrons, ions, neutrals and excited atoms, radicals and molecules. Many of these may have to be taken into account for a successful treatment of the wool. OES data, which are monitoring excited particles show large fluctuations in the line intensities. The main reason for this is that the pressure does not remain constant during the plasma treatment. DLP measurements suffered the same problem. Additional problems occurred because the probe surface became contaminated during the measurement. In contrast, the relative intensities of mass lines obtained from quadrupole mass spectrometry (MS) turned out to be a good indicator for the intensity of the plasma treatment of wool.