Simultaneous Cotton-Mouton and Faraday rotation angle measurements on JET

A. Boboc, L. Zabeo, A. Murari

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Abstract

The change in the ellipticity of a laser beam that passes through plasma due to the Cotton-Mouton effect can provide additional information on the plasma density. This approach, complementary to the more traditional interferometric methods, has been implemented recently using the JET interferometer-polarimeter with a new setup. Routine Cotton-Mouton phase shift measurements are made on the vertical central chords simultaneously with the Faraday rotation angle data. These new data are used to provide robust line-integrated density measurements in difficult plasma scenarios, with strong Edge Localized Modes (ELMs) or pellets. These always affect interferometry, causing fringe jumps and preventing good control of the plasma density. A comparison of line-integrated density from polarimetry and interferometry measurements shows an agreement within 10%. Moreover, in JET the measurements can be performed close to a reactor relevant range of parameters, in particular, at high densities and temperatures. This provides a unique opportunity to assess the quality of the Faraday rotation and Cotton-Mouton phase shift measurements where both effects are strong and mutual nonlinear interaction between the two effects takes place. © 2006 American Institute of Physics.
Original languageEnglish
Article number10F324
Pages (from-to)-
JournalReview of Scientific Instruments
Volume77
Issue number10
DOIs
Publication statusPublished - 2006
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Instrumentation

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