Resolving discharge parameters from atomic oxygen emission
Pedro Viegas, Luca Vialetto, Alex van de Steeg, A. Wolf, W.A. Bongers, G.J. van Rooij, M. C. M. van de Sanden, P. Diomede, F J J Peeters
Abstract
Abstract A method is proposed to spatially resolve discharge parameters from experimental measurements of emission intensity and 1D numerical simulations including an O atom collisional-radiative model. The method can be used for different plasmas and conditions. Here, contracted microwave discharges for CO 2 conversion are studied at intermediate to high pressures (100–300 mbar). Radial profiles of electron density ( n e ) are used as input in the model and corrected to successfully simulate the measured Gaussian profiles of emission intensity of the 777 nm transition ( I 777 ). As a result, radially-resolved parameters inaccessible in experiments, such as n e , power density ( P abs ), electron temperature ( T e ), electric field and reaction rates, are numerically-obtained for several conditions. n e and P abs approximately follow Gaussian profiles that are broader than that of I 777 . For pressures below 150 mbar, the difference in full width at half maximum is typically a factor 1.6. This consists in a phenomenon of optical contraction, which is due to concave profiles of O molar fraction and T e . The implications of the simulated profiles on the study of plasmas for CO 2 conversion are discussed and it is shown that these profiles allow to explain high reactor performances at low pressures.