Bochum 2015 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 25: Low Temperature Plasmas III
P 25.6: Vortrag
Donnerstag, 5. März 2015, 11:55–12:10, HZO 30
Mass spectrometry of ions originating from atmospheric pressure plasmas — •Simon Große-Kreul, Simon Hübner, Gert Willems, Jan Benedikt, and Achim von Keudell — RD Plasmas with Complex Interactions, Ruhr-Universität Bochum
The investigation of ions originating from atmospheric pressure plasma (APP) sources plays an important role to understand their interaction with both liquid and solid samples. Mass spectrometry is a powerful diagnostic tool for the characterization of APPs. However, the process of ion sampling is a challenging task since the sampling orifice has to be small in order to avoid penetration of the plasma sheath into the vacuum system leading to distorting effects. Positive ions created by an APP jet operated with He and small (<2 %) admixtures of N2 and O2 are extracted from the effluent through a sampling orifice (20 µm) into a differentially pumped vacuum system. An ion lens is mounted in the first pumping stage and is used to extract and focus sampled ions into the second stage containing a quadrupole mass spectrometer. Ion trajectory simulation reveals an ion energy of less than 0.5 eV which shows that the analyzed ions are originating from the plasma. Water cluster ions of the form H+(H2O)n are dominating the mass spectrum in the case that the feed gas is not further purified. A Significant signal of NO+ can be observed even with highly purified feed gas depending on the operating conditions. This is attributed to the low ionization energy of NO of only 9.26 eV which causes it to win in charge transfer reactions during the sampling process.