Spectroscopic diagnostics of an atmospheric microwave plasma for monitoring metals pollution

A 1.5 kW, 2.45 GHz microwave sustained plasma in a flowing sample of stack exhaust gas has been shown in recent Department of Energy/Environmental Pro tection Agency testing to be an accurate monitor of trace hazardous metals (in the ppb range) such as lead, chromium, and beryllium. Optical-ultraviol et spectroscopic studies are being carried out to better understand this pa rticular atmospheric pressure plasma torch. An experimental device has been modified with extra visible access for radial and axial profile measuremen ts. Diffraction limited fiber optic plasma views and high-resolution gratin g spectrometer instrumentation for molecular rotational and atomic excitati on temperature (T-rot, T-exc) measurements are being used for plasma studie s. Initial chord averaged measurements have been made of the N-2(+) (0,0) f irst negative system for T-rot and Fe I levels for T-exc in nitrogen and ai r plasmas, respectively. (C) 1999 American Institute of Physics. [S0034-674 8(99)52401- 5].