Optimization of Remote Inductively Coupled Plasma for the Cleaning of Different Optical Surfaces

This work deals with different experimental approaches based on the low-pressure RF downstream ICP plasma, where different test objects were cleaned using specific plasma configurations. Among the cleaned test objects are: B4C-coated optics, Al EUV filters, Au, Al, Ni, Rh materials and Au coated optics. The present study is based on the analysis  of  different plasma configurations such as Ar, O2, O2/Ar, H2/Ar, N2/O2/H2 and N2/O2/H2 feedstock gases by using a commercial plasma source, the model GV10x produced by ibss Group Inc.

The first part of this work consists of an overview with information on the plasma-related cleaning applications and accelerator-based light sources. The second part gives a detailed experimental description including the different techniques used not only to characterize the optical coating and materials, but also on how to use the pertinent plasma diagnostics performed on some plasma configurations in the context of this study. Subsequently, the results from the cleaning of different optical coatings such as among others Al and B4C are shown. The thesis concludes with the results from the in-situ plasma cleaning of a copy mirror with similar characteristics than the mirror M1 from the CIRCE beamline at ALBA Synchrotron. The carbon contamination was successfully removed form that mirror optical surface, which indicates the importance of this application for the future process at ALBA as well as at other accelerator-based light source facilities. In this specific plasma cleaning run, additional unexpected – but nevertheless scientifically relevant - issues were also found and will thus be discussed.

Thesis supervisor: Eric Pellegrin


Thesis tutor: Javier Rodríguez Viejo