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Description
A phase-modulated dispersion interferometer combined with a polarimeter is currently being designed in ITER. This diagnostic, called DIP (Density Interferometer Polarimeter), aims at performing reliable electron density (ne) measurements with a time resolution of 1 ms and an accuracy of 10% during ramp up/down phases, and 2% during flat-top, serving as a complementary system for ITER’s main ne diagnostic, the TIP (Toroidal Interferometer/Polarimeter) [1]. ITER’s DIP is based on a CO2 laser (λ = 9.6 μm). It is inherently insensitive to mechanical vibrations and, thanks to the combined polarimeter, can correct fringe jump errors [2]. Phase-modulation is performed using a photo-elastic modulator (PEM) [3].
This work presents recent updates on the system design and synthetic diagnostic development. In particular, a model that takes into account the variations of air [4] and ZnSe optical windows [5] refractive index due to environmental parameters (temperature, pressure and humidity), eventually affecting phase measurements, is here described.
Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization
[1] M. A. Van Zeeland et al Rev. Sci. Instrum. 89, 10B102 (2018)
[2] T. Akiyama et al Rev. Sci. Instrum. 87, 11E133 (2016)
[3] T. Akiyama et al Rev. Sci. Instrum. 81, 10D501 (2010)
[4] R. J. Mathar 2007 J. Opt. A: Pure Appl. Opt. 9 470
[5] H. H. Li J. Phys. Chem. Ref. Data 13, 103–150 (1984)
