Three dimensional distribution of impurity emission in the edge region of LHD obtained by single field-of-view tomography

Abstract

Three dimensional (3D) distribution of impurity emission intensity is obtained from two dimensional (2D) image using newly developed single field-of-view tomography scheme. Spectrometer with multi-channel fiber array views the entire edge region of stochastic magnetic layer of LHD, including divertor plates, divertor legs, the stochastic layer, and the last closed flux surface. The tomography scheme introduces new regularization terms in Lagrangian function, based on the transport feature in magnetized plasma that the emission assumed to be smooth along the magnetic field due to the very fast parallel transport compared to the transport across the magnetic field. Feasibility of the scheme is checked with test emission distributions. The scheme is applied to the experimental data in LHD, where the impurity emission distribution of different charge states and of different electron densities are obtained in relation to the magnetic field structure in the edge stochastic layer.