scispace - formally typeset
Search or ask a question

Showing papers on "Polarimetry published in 1976"


Journal ArticleDOI
TL;DR: In this article, the results of the recent observations of interstellar circular polarization are applied to a study of the galactic magnetic field, and the results are compared with what has already been learned from linear polarization observations.
Abstract: Recent observations of interstellar circular polarization are applied to a study of the galactic magnetic field. The results are compared with what has already been learned from linear polarization observations.

12 citations


Journal ArticleDOI
TL;DR: In this paper, two distinct and general definitions of ellipsometry and polarimetry are stated ab initio that account for the existing duality in usage of both terms and contrast these commonly used similar terms against one another.

10 citations


Journal ArticleDOI
TL;DR: In this article, a portable astronomical polarimeter system employing a photoelastic modulator and digital synchronous detection to extract simultaneously three of the four Stokes' parameters of the incident light is described.
Abstract: We describe a portable astronomical polarimeter system employing a photoelastic modulator and digital synchronous detection to extract simultaneously three of the four Stokes' parameters of the incident light. Light polarization by the telescope optics is the major systematic offset error. A mini-computer is employed for data handling, control, and quick-look Fourier transformation of time-series data.

4 citations


Journal ArticleDOI
TL;DR: In this article, a general procedure based on Mueller matrices and Stokes vectors is applied to investigate the phase shifts and instrumental polarization of a five-mirror coude system, and it is concluded that very accurate absolute polarimetry is probably impossible with a complicated coude focus, but relative measurements of the variation of polarization with wavelength can still be made with reasonable accuracy.
Abstract: The coude focus is a poor focus to use for polarization observations because the intervening flat mirrors can considerably change the polarization properties of starlight. The present paper is intended to serve as a guide for the study of a coude system prior to its employment in polarization measurements and also for the later interpretation of the observations. Polarization characteristics of aluminized mirrors are studied experimentally, with consideration given to the uniformity of phase shifts on different parts of a mirror, the wavelength dependence of phase shifts, aging effects, and spurious linear polarization. Modifications of partially polarized starlight by a coude system are analyzed using a general procedure based on Mueller matrices and Stokes vectors; the method is then applied to investigate the phase shifts and instrumental polarization of a five-mirror coude system. It is concluded that very accurate absolute polarimetry is probably impossible with a complicated coude system, but relative measurements of the variation of polarization with wavelength can still be made with reasonable accuracy.

4 citations


Journal ArticleDOI
TL;DR: In this paper, a method is described for correcting the error in the measurement of a Faraday rotation in propagation from a geostationary satellite by calibrating the receiving system.
Abstract: Sources of error in polarization measurements on electromagnetic waves are investigated. A method is described for correcting the error in the measurement of a Faraday rotation in propagation from a geostationary satellite by calibrating the receiving system.

4 citations



R. S. Wolff1
01 Aug 1976
TL;DR: In this paper, a spectrometer and a polarimeter consisting of large-area panels of mosaic crystals have been constructed and prepared for use in the OSO-8 satellite for study of stellar and solar X-ray spectra between 1.8-8 keV and stellar Xray polarization at 2.6 keV.
Abstract: A spectrometer and a polarimeter consisting of large-area panels of mosaic crystals have been constructed and prepared for use in the OSO-8 satellite. The instrumentation is planned for study of stellar and solar X-ray spectra between 1.8-8 keV and stellar X-ray polarization at 2.6 keV. Aspects of the design which enable the instrument to make measurements of the diverse range of stellar and solar phenomena are described. Some of the unique features, such as high sensitivity, high temporal resolution, and spectral range, are discussed. The applicability of the spectrometer and polarimeter to various current problems in X-ray astronomy is considered.

1 citations





Journal ArticleDOI
TL;DR: A quadrupole Fe57 polarimeter consisting of single crystals of LiNbO3 : CoJ7 as source (polarizer) and of Fee03 (siderite) as absorber (analyzer) is described in this article.
Abstract: A quadrupole Fe57 polarimeter consisting of single crystals of LiNbO3 : CoJ7 as source (polarizer) and of Fee03 (siderite) as absorber (analyzer) is described. The quadrupole interactions of the two materials are nearly equal in magnitude but opposite in sign and in addition the asymmetry parameter q ss 0. The polarization dependence in Mossbauer spectroscopy has been worked out in a number of theoretical treatise [I-101 and various techniques have been used to carry out polarimetry experiments, mostly based on transversely magnetized Co57 a-Fe sources [lo-271 and/or by selective excitation of nuclear sublevels [28] or filter techniques [13, 29-32]. These methods have disadvantages and difficulties are encountered in the analysis of the spectra. In the former case by the multiplicity resulting from the six linearly polarized source lines and in the latter cases by the inefficiency of the selective excitation or of the filters in terms of intensity, degree of polarization and non-Lorentzian lines. Sources exhibiting quadrupole hyperfine interaction will circumvent some of these problems. The usefulness of a quadrupole split Co57 source for a polarimeter depends on the fulfillment of the following conditions : 1. The material can be grown as single crystal and cutting of thin plates in various directions is


Book ChapterDOI
01 Jan 1976
TL;DR: In this paper, the polarimeter system with an on-line particle identification system is described. But this system is not suitable for high resolution in energy and vice-versa.
Abstract: Polarimetry based on double scattering techniques usually use carbon or helium on polarization analysers. But this limits the polarimeter efficiency when high resolution in energy is sought and vice-versa. The polarimeter system we have developed overcomes these limitations by using a silicon analyser which acts as a ΔE detector at the same time. Basically the polarimeter consists of a lmm thick silicon ΔE detector and two silicon stopping detectors for detecting L and R scattered particles at 28°, and another detector behind the analyser used in anticoincidence to eliminate the unscattered particles as shown in fig. 1. The basic design of the polarimeter has already been described 1). We have devised a system to use the polarimeters (one on each side of the beam) with a PDP-9 computer on-line. Three 400-channel pulse height analysera. each with its memory divided in halves are used to record ΔE1,2, E1L,R and E2L,R pulses respectively. The ADC outputs corresponding to these signals give the energy deposited by the reaction products in ΔE detectors and their total energy respectively. The primary data are stored on-line and written on a magnetic tape as records consisting of 133 events, each event being defined as three channel conversions in coincidence from three ADC’s. The basic logic is to record a new event whenever there is an acceptable signal in any one of the ΔE detectors, ADC1 simultaneously with a signal in any of E detectors, ADC2 or ADC3. This event corresponds to a new channel conversion only in one of the E ADC’s depending on ΔE signal location in the first ADC, the previous channel conversion being repeated for the other E ADC. The separation of these events into those due to protons and to other particles, for each detector telescope,is done setting energy windows on ΔE and E channel conversionsto match with the energy loss in the analyser detectors and the total energy of these particles,as determined from the reaction kinematics. Thus this technique enables one to identify the reaction products and obtain their energy spectra without using analog particle identifying circuits. This type of polarimeter with an on-line particle identification system can play an important role in polarization measurements involving low count rates,as generally is the case in double scattering, triple scattering and in simultaneous measurements of asymmetries when more than one type of particles is produced in a nuclear reaction. The system described here is easily adaptable to handling four polarimeters simultaneously without changes. With larger ADC’s it can handle easily eight to sixteen polarimeters.

Journal ArticleDOI
TL;DR: The instrument described by West uses a rotating analyzer, which absorbs at least half the incident unpolarized light, which is a serious disadvantage in most astronomical applications.
Abstract: The instrument described by West uses a rotating analyzer, which absorbs at least half the incident unpolarized light. This light loss, avoided in our polarimeter, is a serious disadvantage in most astronomical applications. Nevertheless, the polarimeters with rapidly rotating analyzers were often used in astronomical studies. Besides light loss, their disadvantage is a need of placing a depolarizer between the analyzer and detector to eliminate the effects of dependence of detector sensitivity on polarization. The depolarizer is even more essential if the analyzer is placed in front of a grating spectrometer, the transmittance of which usually depends strongly on polarization. However, a satisfactory monochromatic depolarizer remains to be invented. The crystal depolarizers in which the light is split on a crystal surface into two perpendicularly polarized beams cannot be used because the distribution of illumination on the detector, having usually nonuniform sensitivity, would depend on polarization of light incident on the depolarizer.

Journal ArticleDOI
TL;DR: In this article, the polarization parameters of optical radar signals, which are characterized by parameters resulting from entropy of partially polarized light waves, are discussed and the properties of the signal can be represented by a factor which is a ratio of entropies, and by two parameters of the polarization ellipse.
Abstract: The polarization parameters of optical radar signals, which are characterized by parameters resulting from entropy of partially polarized light waves, are discussed. It is shown that the properties of the signal can be represented by a factor which is a ratio of entropies, and by two parameters of the polarization ellipse. The proposed method using quasilinearly polarized signals of He-Ne laser at 632.8 nm was applied to the investigations of a number of typical materials.