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Optical Layout and Alignment Methods for Visible Tomography and Emission Spectroscopy Diagnostics in SPIDER

SPIDER, a prototype negative ion source with low voltage extraction for the ITER neutral beam injector will be equipped with a set of diagnostics to qualify and optimize the neutral beam for ITER. In particular, the visible tomography diagnostic will estimate the uniformity of the beam using a set of linear charge-coupled device cameras, while emission spectroscopy will measure the spatial variation of plasma parameters in the RF plasma source and evaluate the divergence of the extracted beam, analyzing the spectrum collected over multiple lines of sight (LOS). This paper presents the optical layout of the LOS and detection heads of tomography and spectroscopy and the required accuracy in their alignment, proposing also alignment criteria.