Evaluation of the spatial structure of multiline emission in a capacitively coupled plasma using tomographic reconstruction

Abstract

By imaging a capacitively coupled plasma from multiple directions using telecentric lens cameras and optical bandpass filters, the spatial structure of emission at specific wavelengths was reconstructed using the Tikhonov–Phillips regularization method. Camera parameters, crucial for relating three-dimensional structures to two-dimensional images, were evaluated experimentally to avoid a complex analytical approach. Assuming an axisymmetric emission profile, 750.4 nm Ar and 585.2 nm Ne emissions from Ar/Ne mixture plasma were reconstructed. The pressure dependence of the reconstructed Ar profile showed a similar trend to that of the two-dimensional emission images. The spatial structure of the emission intensity ratio of Ne to Ar from the reconstructed Ar and Ne profiles agreed well with a spatial distribution of electron temperatures measured with a Langmuir probe.