In this review of plasma polarimetry, first the theory is discussed in general, then exact analytic solutions of the evolution equation for polarization are presented, as well as approximate analytic solutions. Numerical integration of the evolution equation is also discussed.The design of experiments is then considered taking into account the maximum amount of information which can be obtained from polarimetric measurements. Special attention is devoted to the techniques of polarization modulation (including both progressive and alternating modulation). Different alternative configurations are described which are of special interest because they can be realized in the far infrared and because they allow a measurement of phases rather than amplitudes. The effects of refraction are then briefly considered. Finally, the combination of polarimetry and interferometry on the same instrument is discussed, including the effects of polarization modulation.
The state of polarization of radiation scattered from hot plasma for any given input polarization is obtained by a relativistic derivation. Approximate analytical expressions are obtained for electron temperatures below about 10 keV. The characteristics of the scattered polarization are presented in detail for fully and linearly polarized incident radiation and their implications for the design of experiments are discussed.
A formalism is presented for treating plasma polarimetry when both the Cotton–Mouton and the Faraday effects are large. For this general case it is shown that, for each measuring chord, up to nine parameters related to the plasma can be determined, instead of the usual single Faraday rotation. These parameters can be measured by a convenient modulation of the polarization state of the input radiation, and they can be used in the reconstruction of the magnetohydrodynamic equilibrium. Thus, the potential of the polarimetric diagnostic can be significantly increased, and the range of plasma conditions where the latter can be used, is extended. The importance of refraction is discussed.
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