Measurement of density profiles using the new infrared scanning interferometer for FTU

A scanning interferometer has been developed and installed on the FTU tokamak for plasma density profile measurements. A scanning system is equivalent to a multi-chord system while keeping the optical scheme as simple as a single-chord interferometer. This new diagnostic has achieved a spatial resolution of ∼1 cm and a time resolution of 62 μs. In this paper, we present the first measurements carried out with this interferometer showing its peculiar capabilities. Particular care has been paid to the analysis of pellet fuelled discharges, where the fast and large density change (1021/m3 in 100 μs) is a great challenge for the system. Results and problems with the inversion are reported. Comparison with other FTU diagnostics is also presented