Journal article

Reconstruction of ion temperature profiles from single chord NPA measurements on the TCV tokamak

The flux of charge exchange ( CX) neutrals measured by neutral particle analysers ( NPAs) is the line integral along the viewline of the NPA and contains information about the ion energy distribution of the observed plasma. On the Tokamaka a Configuration Variable ( TCV) a single chord NPA is used to scan the plasma cross section by vertically displacing a reproducible discharge across its fixed line of sight. The ion temperature inferred from the passive CX flux as a function of the distance of the NPA chord to the magnetic axis is used to obtain an ion temperature profile T-i(rho). To model the neutral source, simulations of neutral particle penetration from the edge and the neutralization processes are reported. In plasmas with thermalized ion populations, the NPA hydrogen or deuterium temperature profiles agree with the carbon ion temperature profile measured by charge exchange recombination spectroscopy. Matching the simulation with synchronous NPA measurements of two plasma species provides absolute profiles of neutral particles densities and the isotopic composition of the plasma, which are required for the transport analysis. With further modelling, the ion temperature profile may be iteratively reconstructed from the CX spectrum without displacing the plasma.


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