Showing papers on "Polarimetry published in 1975"

Stellar and Solar X-Ray Polarimetry

Abstract: Astronomical stellar and solar studies involving X-ray polarimetry are discussed along with the statistical limitations inherent in polarimeter measurements and the design principles of a number of polarimeter types. Attention is given to photoelectric polarimeters, secondary fluorescence X-ray polarimeters, Borrmann-effect polarimeters, circular polarization analyzers, gamma-ray polarimeters, and multilayer reflection polarimeters. Bragg crystal polarimeters are considered, taking into account the theory of the polarimeter operation, aspects of instrument design, and the occurrence of systematic errors. The design and the performance of a rocket and a satellite Thomson-scattering polarimeter are also examined.

Stellar and solar X-ray polarimetry

Abstract: The scientific motivation for X-ray polarimetry is discussed with particular emphasis on the information that might be obtained on binary X-ray pulsars and a number of other classes of objects, including solar flares. Detailed discussions are given for Thomson-scattering and Bragg-crystal polarimeters with numerical estimates for the sensitivity of various existing and proposed instruments.

Determining several optically active components in a single sample - using a series of polarimetric determinations

Abstract: The concentration of several optically active substances, occurring together in a single sample, is determined by measuring the optical rotation by multiple polimetry at different wave lengths. The number of polimeter measurements should at least be equal to the number of optically active substances present in the sample and by this means the values of the concns. of the various components are determined. The measurements may be made consecutively or simultaneously. An automatic polarimeter which measures at several wavelengths is used. the angular measuring system of which is connected directly, or indirectly vian an electronic stone, to a computer. It has an automatically adjustable revolving filter. The computer is linked to a data logger and can have an optical signal also. Method is used for determining the composition of multi-component mixtures when these are optically active and of known properties. The use of polarimetry has been limited because only one component could be measured at one time. The system described allows the break down of such a mixture to give the conc. of the various components.

Focusing crystal polarimeter designed for x-ray polarimetry: construction and performance

Abstract: A method for the construction of a graphite crystal polarimeter designed for measuring linear polarization of X-ray continuum sources is described. The dependence of reflected intensity upon the polarization direction of the incident beam at Bragg angles of 45 deg is used to measure the polarization. The particular instrument described was designed for a satellite X-ray polarimeter. By using a focusing parabolic surface instead of a nonfocusing flat crystal, the signal-to-background ratio is improved by a factor of 30 as compared to a flat crystal polarimeter of the same effective area. The focusing properties of the reflector were tested both optically and with X-rays. The performance of the instrument as a polarimeter was tested with a continuum X-ray source of small polarization, which was independently measured by a single flat crystal polarimeter. The agreement between the two measurements is excellent, indicating that the instrument can measure polarizations as low as 0.3%.

Influence, detection, and measurement of depolarization in Hertzian reflecto‐polarimetry and reflecto‐ellipsometry

Abstract: Radar specialists know that during the reflection of waves the phenomenon of depolarization appears in a more or less intense manner depending upon atmospheric conditions. The measurement of depolarization in a laboratory setting is difficult because the problem involves measuring a weak, incoherent energy superimposed upon a strong, coherent energy, and standard instruments have not been conceived to effect such a measurement. The author first studies the influence of wave depolarizations upon reflectometric measurements made at normal incidence in standard rectangular guides, then he indicates how, by using an interferometer, one can perform the measurement of the coherent and incoherent energy. In the second part of his report, he studies the influence of wave depolarizations made during reflection at an oblique angle (for example, the measurement of the Brewster angle). He then indicates a type of interferential analyzer (a two‐ or a three‐wave) employed with a polarization duplexer which enables one to measure, or to record (with a three‐wave interferometer), depolarization as well as the rotation and ellipticity of the reflected coherent energy. Finally, in the third part, the author considers the case of reflection made at normal incidence in circular waveguides (mode TE11). He is led to propose an interferential reflecto‐polarimeter–ellipsometer having as its principal element a ’’lossy’’ turnstile junction, the properties of which he outlines briefly. He shows that this instrument will enable one to achieve the measurement and recording (when associated with a three‐wave interferometer) of depolarization as well as of the rotation and ellipticity of the coherent part of the reflected wave.

Potential implications of x‐ray polarimetry of binary sources

Abstract: Interesting inferences that could, in principle, be drawn from cosmic x-ray polarimetry experiments of the type being currently planned are summarized. 34 references. (auth)