Absolutely calibrated mass spectrometry measurement of reactive and stable plasma chemistry products in the effluent of a He/H2O atmospheric plasma. (27th July 2017)

• Record Type: Journal Article
• Authors: Willems, Gert; Benedikt, Jan; von Keudell, Achim
• Is Part Of: Journal of physics. Volume 50:Number 33(2017)
• Publication Date: 2017-07-27
• Subjects: cold atmospheric plasma -- atmospheric pressure plasma jet -- OH radical -- H2O2 -- MBMS -- TIMS; Physics -- Periodicals; 530
• DOI: 10.1088/1361-6463/aa77ca
• Languages: English
• ISSNs: 0022-3727

Abstract

Abstract: Mass spectrometry has been used to analyse the effluent of a micro-scaled atmospheric plasma jet operated in helium with a controlled concentration of water vapour. Absolute densities of H2 O2 and OH have been measured as function of water vapour concentration and distance from the jet nozzle. The trend for both species densities are correlated and after an initial increase, the densities of H2 O2 and OH saturate around 5000 ppm to 6000 ppm of water admixture. The largest densities for H2 O2 ( 2.37 × 10 14 c m − 3 ) and OH ( 1.96 × 10 14 c m − 3 ) were measured at 7980 ppm water admixture and 2 mm distance from the jet. Densities of HO2 ( 1 × 10 14 c m − 3 ) and O2 ( 4 × 10 14 c m − 3 ) have been measured as well, although no trend could be observed. The direct electron impact ionisation cross-section of H2 O2 at 70 eV electron energy was experimentally determined to be 1.02 × 10 − 16 c m 2 . The measured densities and profiles have been compared to a 2D axially symmetric fluid model of species transport and recombination reactions. The effluent reaction chemistry is dominated by the hydroxyl radical, where the hydrogen atoms seem to play an important role as well. The analysis of neutral plasma chemistry products have been complemented by measurements of qualitative ion signals.