I. E. Kozhevatov

Method for absolute calibration of reference plates for interferometric inspection of surfaces

A method for absolute calibration of reference plates of interferometers for measuring surface profiles of optical elements is described. It is based on the solution of the inverse problem of reconstruction of a surface profile from the data of relative measurements of three plates by way of minimizing the goal function. The method takes into account the gravitational sagging of the reference plate and allows one to obtain its profile with an accuracy of ∼λ/1000 for λ=6328 Å. The calibration algorithm as well as theoretical calculations and experimental results are presented.

A Fabry-Prot etalon as fourier tachometer

A tachometer for measuring the displacements of the center of gravity of spectral line profiles is developed. The implementation of the device, basically a Fabry-Pérot etalon, is given. The spectral shifts are determined, using the frequency of a laser as reference.

Fourier parameters and moments of polarization profiles of magnetically active lines. Fourier vector magnetograph

A new method is proposed to determine all components of the solar magnetic fields using the cumulants of the profile of a magnetic sensitive line. The method is based on polarization measurements in a number of points of the line profile and subsequent calculation of the amplitudes and phases of its two first Fourier-harmonics.

Second version of the IZMIRAN solar spectromagnetograph. Part I. Instrument design

The second version of the IZMIRAN solar spectromagnetograph (SM), which is designed for measuring the full vector of the magnetic field and the line-of-sight velocities in the solar photosphere, is described. In contrast to the conventional schemes, the described SM uses the parallel analysis of the spectrum and polarization of optical radiation. The latter could be performed thanks to the method of precise calibration of circuits with multielement photodetectors. The new scheme of the SM allows measurements of the Stokes parameters for two magnetically active lines with an accuracy limited by only the quantum noise of photodetectors.

Second version of the IZMIRAN solar spectromagnetograph. Part II. Algorithms for preliminary data processing

A system of experiments and an algorithm for data processing that allow elimination of systematic errors, which are caused by instrument effects of the spectromagnetograph, are described. It is shown that the residual systematic error in measuring the Stokes parameters is approximately three times lower than the statistical errors related to quantum noise of receivers.

A Solar Spectromagnetograph

A new solar spectromagnetograph for measuring the full magnetic-field vector and line-of-sight velocities is described. A new version of a polarization analyzer ensuring parallel measurements of six polarization components of spectral lines is considered. The spectromagnetograph allows the use of any algorithms for obtaining the magnetic fields vector, in particular, the Babcock algorithm and the Fourier transform technique. The sensitivity of the instrument for the longitudinal and transverse magnetic field is ∼ 3–5 and ∼ 20–30 G, respectively, and ∼10 m/s for the line-of-sight velocities.

Reducing the influence of the premonochromator on the stability of fourier spectrometers

A method is proposed to improve the stability of specialized solar Fourier spectrometers. The method is based on matching the premonochromator bandwidth with the Fourier harmonic frequency of the spectrometer. It is shown that this matching is efficient for both decrease of the measurement errors due to premonochromator instabilities and increase of the linearity of the measurement range. Some possible applications of this procedure for slot spectrometers and Fabry-Perot interference filters are considered.

Apparatus Weighting Functions in measuring the line-of-sight velocities by the ‘center of gravity’ method

The conception of the Apparatus Weighting Function (AWF), numerically characterizing the contributions of different layers of the solar atmosphere to indications of the apparatus used is introduced. For the detection of line-of-sight velocities, measuring the shifts of the ‘center of gravity’ of a spectral line profile, AWFs have been calculated for several single lines used by the authors in their observations of the photospheric velocity field. A comparison of AWFs is given for instruments, based on the principles of measuring both the ‘center of gravity’ shifts and intensity differences in the line wings.