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1

Application of the gradient method for polarimetric data inversion

Chrzanowski J.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2012

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nr 31 (103)

55-61

EN

Gradient procedure is suggested, which allows to fit multi-parameter theoretical model to multi-channel experimental data obtained by means of polarimetric measurements. Procedure deals with nonlinear system of differential equations that describe the evolution of an electromagnetic wave in a hot plasma and provides sufficiently fast convergence to stationary values. The procedure is illustrated with numerical calculations in the case of one and two measurement channels, that allow to retrieve two and four of plasma parameters respectively.

2

Unconventional procedure for inversion of polarimetric data: numerical calculation for a simple model of toroidal plasma

Chrzanowski J., Kravtsov , Y. A., Mazon D.

Nukleonika

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2012

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Vol. 57, No. 1

37-41

EN

A gradient method is proposed for inversion of polarimetric data for tokamak plasma. It is assumed that the electron density and the normalized magnetic profile along the ray are known from experiments (scattering and magnetic measurements) in the spirit of the EFIT approach. Under these assumptions the maximum value of the electron density and maximum value of the magnetic field may be estimated by the gradient method. It is shown that with this method it is possible to achieve accuracy of about 0.1% already after 3-4 iterations.

3

Modulation of weak Cotton-Mouton effect in conditions of strong Faraday rotation

Kravtsov Y. A., Chrzanowski J.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2011

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nr 26 (98)

47-51

EN

Evolution of polarization state is described by new mathematics, namely, by angular variables technique (AVT) which describes behavior of the angular parameters of polarization ellipse in magnetized plasma. From this point of view the polarization of electromagnetic waves in magnetized plasma is studied in conditions, when Cotton-Mouton effect is weak enough as compared with Faraday one. The method of consequent approximations is applied, which uses the ratio of Cotton-Mouton [omega], and Faraday [omega]3 parameters, as a small parameter of a problem and allows obtaining simple analytical expressions for ellipticity angles approximations.

PL

Przy pomocy nowego modelu matematycznego – techniki zmiennych kątowych (AVT), opisana jest ewolucja stanu polaryzacji z ukazaniem zachowania kątowych parametrów elipsy polaryzacji w namagnetyzowanej plazmie. Z tego punktu widzenia analizowany jest stan polaryzacji wiązki elektromagnetycznej w warunkach, gdy efekt Cottona-Moutona jest niewielki w porównaniu z efektem Faradaya. Zastosowana metoda kolejnych przybliżeń pozwala wykorzystać stosunek parametrów [omega] (Cotton-Mouton), oraz [omega]3 (Faraday), jako kolejny, mały parametr, pozwalający uzyskać proste analityczne wyrażenia dla kątów opisujących stan elipsy polaryzacji.

4

Possible accuracy of the Cotton-Mouton polarimetry in a sheared toroidal plasma

Kravtsov , Y. A., Chrzanowski J.

Nukleonika

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2011

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Vol. 56, No. 2

175-177

EN

The Cotton-Mouton effect in the sheared plasma with helical magnetic lines is studied, using the equation for the complex amplitude ratio (CAR). A simple model for helical magnetic lines in plasma of toroidal configuration is suggested. Equation for CAR is solved perturbatively, treating the shear angle variations as a small perturbation, caused by the spiral form of the magnetic lines. It is shown that the uncertainty of the polarization measurements in the toroidal plasma with a spiral form of the magnetic lines does not exceed 1.0–2.0%, which determines the limiting accuracy of the Cotton-Mouton polarimetry. It is furthermore pointed out that the method of a priori subtraction of the “sheared” term may significantly improve the accuracy of the Cotton-Mouton polarimetry.