title: Fringe jump analysis and implementation of polarimetry on the ASDEX Upgrade DCN interferometer.
abstract: The ASDEX Upgrade tokamak is equipped with a 5-channel DCN interferometer with a probing wavelength of 195 μm. Up to now, phase measurement and density calculation have been accomplished by hard-wired phase counting electronics. Meanwhile, a fast digitizer has been installed which acquires the raw signals. That way, the various causes of counting errors by integer multiples of 2π, so-called fringe jumps, can be analyzed, and phase reconstruction schemes based on digital signal processing can be developed. In addition, a prototype polarimeter setup has been installed on one channel and allows for measurement of the Faraday rotation experienced by the probing beam.
authors.affiliation: Max-Planck-Institute for Plasma Physics, Garching 85748, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Mlynek
authors.affiliation: Max-Planck-Institute for Plasma Physics, Garching 85748, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Casali
authors.affiliation: Max-Planck-Institute for Plasma Physics, Greifswald 17491, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Ford
authors.affiliation: Max-Planck-Institute for Plasma Physics, Garching 85748, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Eixenberger