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P: Plasmaphysik

P 4: Diagnostik 1; Niedertemperaturplasmen / Plasmatechnologie 2; Magnetischer Einschluß 2

P 4.1: Poster

Montag, 27. März 2006, 17:00–19:00, Flure

Cavity Enhanced Spectroscopy as a Diagnostic for Micro Particles in a Plasma — •G. Thieme¹, R. Basner¹, J. Ehlbeck¹, J. Röpcke¹, H. Kersten¹, J.P. Reid², and P.B. Davies³ — ¹Institut für Niedertemperatur-Plasmaphysik, F.-L.-Jahn-Str. 19, 17489 Greifswald, Germany — ²School of Chemistry, University of Bristol, Bristol BS8 1TS, UK — ³Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB21EW, UK

Cavity enhanced spectroscopy has been successfully used as a diagnostic for aerosol droplets [1].

We investigate the feasability of applying this technique to solid micron sized particles levitated in an rf-plasma. A pulsed laser is used to excite whispering gallery modes (cavity resonances) in individual microspheres leading to enhanced Raman scattering at corresponding wavelenghts. This non-invasive method gives direct access to the size and also the chemical composition of the microspheres, and is so very interesting for the characterisation of growing layers deposited on micro particles i.e. in molecular plasmas.

We use a capacitively coupled rf-discharge (13,56 MHz) containing an adaptive electrode, above which the micro particles are trapped. The adaptive electrode is divided in ca. 100 square segments which can be biased individually with a DC-voltage allowing specific manipulation of the particle position.

[1] R. Symes, R.M. Sayer, and J.P. Reid, Phys. Chem. Chem. Phys., 2004, 6, 474.