Optical emission tomography:looking into plasmas with complex structures

Measuring the light emitted by a plasma often offers a convenient way to obtain information on the plasma properties. To procure these plasma properties, as well as their spatial distribution in a volume discharge, the local emission coefficient is required. However, the intensity recorded by a detector is a lateral scan of the emission integrated along a line-of-sight. A commonly used technique to retrieve radial dependence in case of cylindrical symmetry is Abel inversion. When the discharge structure exhibits a more complex symmetry or no symmetry at all, a more generalised approach is required: the inverse Radon transform. Since optical access from numerous angles is now required, this technique is especially applicable to discharges in open air. A brief explanation of the Radon and inverse Radon transforms is given and the reconstructed local emission coefficient of a structured volume dielectric barrier discharge (DBD) in open air is presented. Finally, the local emission coefficient is compared to the local electric field strength obtained from simulations