'Complete' far-infrared polarimetry measurements at JET

|p B which is proportional to the Faraday rotation angle of the plane of polarization. This ‘traditional’ polarimetry provides important data to calculate the q-profile, but does not exploit the method completely: The output ellipticity of the beam, generated by the Cotton-Mouton effect (birefri ngence of a magnetized plasma), carries line-integrated information on density time s field components perpendicular to the direction of the beam. This concerns ‐ in good approximation ‐ the toroidal field B t alone, which is, in the case of vertical chords, largely constant along the line of sight. is otherwise measured routinely by interferometry with the drawback of fri nge jumps [2]. It is the phase shift Φ ′ between the wave components parallel and perpendicular to = ′