An important issue of localization of neutral particle measurements on LHD [1, 2] has been investigated. Two approaches exist that can be used to achieve locality. The first one is the application of active measurements with an artificially created localized target for the charge exchange process [1, 3]. The second mathematical approach is a combination of the experimental and computational diagnostic techniques to obtain local measurements with a passive non-perturbing method.
A numerical method has been formulated that can be used to restore the radial distributions from line-integrated passive measurements in case when the structure of the nested magnetic surfaces, i.e. the plasma parameter isolines, is known. The problem is reduced to a numerical solution of an integral equation with the kernel determined by the geometry of experiments and the magnetic equilibrium data available from computer modeling, e.g. by VMEC code. The speed of the plasma column vertical angular scan limited by mechanical capabilities of the diagnostic is 1° per 30 s. The required input data set can be obtained by fan-shaped chord measurements by the analyzer described in [1, 2] either during a steady state of a long plasma discharge or during a sequence of identical short plasma discharges in LHD.

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