Cavity ring down detection of neutral hydrogen atoms and negative hydrogen ions in plasmas

M.G.H. Boogaarts, A.H.M. Smets, M.C.M. Sanden, van de, D.C. Schram

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Abstract

The Cavity Ring Down (CRD) technique has been applied for the absolute detection of low density species in two different hydrogen containing plasmas. CRD measurements have been performed in a 10 Hz pulsed capacitively coupled RF H/sub 2/-plasma to detect negative hydrogen ions (H/sup -/) as well as atomic hydrogen in the n=2 state (H(n=2)). A broadband absorption of 3.5*10/sup -6/ per pass due to photo-detachment of H/sup -/ was observed, which corresponds to a H/sup -/ density of 10/sup 16/ m/sup -3/. In addition, CRD measurements on H(n=2) have been performed in the expanding plasma of a cascaded arc, in which H/sub 2/ or C/sub 2/H/sub 2/ is injected. Densities of H(n=2) down to 10/sup 12/ m/sup -3/ have been measured. In both plasmas a severe decrease of the reflectivity of the cavity mirrors over time was observed, which is possibly caused by diffusion of atomic hydrogen into the reflective coating
Original languageEnglish
Title of host publicationFrontiers in low temperature plasma diagnostics III : book of papers ; Saillon, Switzerland, 15.-19.2.1999
Place of PublicationLausanne
PublisherEcole Polytechnique Fédérale de Lausanne
Pages215-218
Publication statusPublished - 1999
EventFrontiers in Low Temperature Plasma Diagnostics III, February 15-19, 1999, Saillon, Switzerland - Saillon, Switzerland
Duration: 15 Feb 199919 Feb 1999

Publication series

NameLRP / Ecole Polytechnique Fédérale de Lausanne
Volume629/99

Workshop

WorkshopFrontiers in Low Temperature Plasma Diagnostics III, February 15-19, 1999, Saillon, Switzerland
CountrySwitzerland
CitySaillon
Period15/02/9919/02/99

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    Boogaarts, M. G. H., Smets, A. H. M., Sanden, van de, M. C. M., & Schram, D. C. (1999). Cavity ring down detection of neutral hydrogen atoms and negative hydrogen ions in plasmas. In Frontiers in low temperature plasma diagnostics III : book of papers ; Saillon, Switzerland, 15.-19.2.1999 (pp. 215-218). (LRP / Ecole Polytechnique Fédérale de Lausanne; Vol. 629/99). Ecole Polytechnique Fédérale de Lausanne.