University, Diss., 2003--Bonn.

The Q-weak experiment aims to measure the weak charge of proton with a precision of 4.2%. The proposed precision on weak charge required a 2.5% measurement of the parity violating asymmetry in elastic electron - proton scattering. Polarimetry was the largest experimental contribution to this uncertainty and a new Compton polarimeter was installed in Hall C at Jefferson Lab to make the goal achievable. In this polarimeter the electron beam collides with green laser light in a low gain Fabry- Perot Cavity; the scattered electrons are detected in 4 planes of a novel diamond micro strip detector while the back scattered photons are detected in lead tungstate crystals. This diamond micro-strip detector is the first such device to be used as a tracking detector in a nuclear and particle physics experiment. The diamond detectors are read out using custom built electronic modules that include a preamplifier, a pulse shaping amplifier and a discriminator for each detector micro-strip. We use field programmable gate array based general purpose logic modules for event selection and histogramming. Extensive Monte Carlo simulations and data acquisition simulations were performed to estimate the systematic uncertainties. Additionally, the Moller and Compton polarimeters were cross calibrated at low electron beam currents using a series of interleaved measurements. In this dissertation, we describe all the subsystems of the Compton polarimeter with emphasis on the electron detector. We focus on the FPGA based data acquisition system built by the author and the data analysis methods implemented by the author. The simulations of the data acquisition and the polarimeter that helped rigorously establish the systematic uncertainties of the polarimeter are also elaborated, resulting in the first sub 1% measurement of low energy ( 1 GeV) electron beam polarization with a Compton electron detector. We have demonstrated that diamond based micro-strip detectors can be used for tracking in a high radiation environment and it has enabled us to achieve the desired precision in the measurement of the electron beam polarization which in turn has allowed the most precise determination of the weak charge of the proton.

This work presents the design, development, and testing of a field portable imaging spectropolarimeter that operates over the short-wavelength and middle-wavelength portion of the infrared spectrum. The sensor includes a pair of sapphire Wollaston prisms and several high order retarders to produce the first infrared implementation of an imaging Fourier transform spectropolarimeter, providing for the measurement of the complete spectropolarimetric datacube over the passband. The Wollaston prisms serve as a birefringent interferometer with reduced sensitivity to vibration when compared to an unequal path interferometer, such as a Michelson. Polarimetric data are acquired through the use of channeled spectropolarimetry to modulate the spectrum with the Stokes parameter information. The collected interferogram is Fourier filtered and reconstructed to recover the spatially and spectrally varying Stokes vector data across the image.The intent of this dissertation is to provide the reader with a detailed understanding of the steps involved in the development of this infrared hyperspectral imaging polarimeter (IHIP) instrument. First, Chapter 1 provides an overview of the fundamental concepts relevant to this research. These include imaging spectrometers, polarimeters, and spectropolarimeters. A detailed discussion of channeled spectropolarimetry, including a historical study of previous implementations, is also presented. Next a few of the design alternatives that are possible for this work are outlined and discussed in Chapter 2. The configuration that was selected for the IHIP is then presented in detail, including the optical layout, design, and operation. Chapter 3 then presents an artifact reduction technique (ART) that was developed to improve the IHIP's spectropolarimetric reconstructions by reducing errors associated with non-band-limited spectral features. ART is experimentally verified in the infrared using a commercial Fourier transform spectrometer in combination with Yttrium Vanadate as well as Cadmium Sulfide retarders.The remainder of this dissertation then details the testing and analysis of the IHIP instrument. Implementation of ART with the IHIP as well as the employed calibration techniques are described in Chapter 4. Complete calibration of the IHIP includes three distinct processes to provide radiometric, spectral, and polarimetric calibration. With the instrument assembled and calibrated, results and error analyses are presented in Chapter 5. Spectropolarimetric results are obtained in the laboratory as well as outdoors to test the IHIP's real world functionality. The performance of the instrument is also assessed, including experimental measurement of signal-to-noise ratio (SNR), and an analysis of the potential sources of systematic error (such as retarder misalignment and finite polarizer extinction ratio). Chapter 6 presents the design and experimental results for a variable Wollaston prism that can be added to the IHIP to vary the fringe contrast across the field of view. Finally, Chapter 7 includes brief closing remarks summarizing this work and a few observations which may be useful for future infrared imaging Fourier transform channeled spectropolarimeter instruments.

The goal of this dissertation research is to develop and demonstrate a functioning snapshot imaging spectropolarimeter for the long wavelength infrared region of the electromagnetic spectrum (wavelengths from 8-12 microns). Such an optical system will be able to simultaneously measure both the spectral and polarimetric signatures of all the spatial locations/targets in a scene with just a single integration period of a camera. This will be accomplished by combining the use of computed tomographic imaging spectrometry (CTIS) and channeled spectropolarimetry. The proposed system will be the first instrument of this type specifically designed to operate in the long wavelength infrared region, as well as being the first demonstration of such a system using an uncooled infrared focal plane array. In addition to the design and construction of the proof-of-concept snapshot imaging spectropolarimeter LWIR system, the dissertation research will also focus on a variety of methods on improving CTIS system performance. These enhancements will include some newly proposed methods of system design, calibration, and reconstruction aimed at improving the speed of reconstructions allowing for the first demonstration of a CTIS system capable of computing reconstructions in 'real time.'

A three-beam heterodyne polarimeter has been designed and constructed to measure line-integrated density and Faraday rotation of accelerated spheromak plasmas in the Plasma Injector 1 and 2 devices (PI-1, PI-2) at General Fusion Inc. Faraday rotation is a function of the local magnetic field and electron density. Therefore, the polarimeter has the potential to provide information on the internal magnetic field of the plasma. A typical spheromak is about 1m in length and is accelerated to speeds on the order of 100km/s. At a bandwidth of 1MHz, the polarimeter can axially resolve the spheromak down to about 10cm. The polarimeter uses a $\nit{CO}_2$ laser that produces a Faraday rotation signal of about $0.5\degrees$ for a typical plasma with density and magnetic field on the order of $\ee{21}\mmt$ and 1T. The Faraday rotation measurement noise floor for a null signal is about $0.1\degrees$. Two important sources of Faraday rotation error are the ellipticity and collinearity of the plasma-immersed beams. These error sources are examined by sending the plasma beams through a rotating optic to mimic the path through a dense, magnetized plasma. The error due to the ellipticity effect has been reduced to below the noise floor by careful alignment and use of zero phase reflectors that minimize elliptical polarization of the beams. Collinearity error has been greatly improved by aligning the beams with a rotating ZnSe wedge. Measurements after the alignment match well with a model Faraday rotation signal generated from magnetic probe measurements. However, beam collinearity continues to be a significant source of error. For regions with strong density gradients, the size of this error can be on the order of the signal magnitude. For future work, steps should be taken to improve the alignment of the two plasma-immersed beams, and to shorten the length of the beam path to further reduce the beam collinearity error. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-04-30 22:17:18.648

Universiẗat, Diss., 2002--Mainz.

The diploma thesis deals with the influence of magnetic and electromagnetic fields on signals transmitted by optical fibers. Subsequently, the results of individual measured values are evaluated and analyzed, which were measured using an interferometer and a polarimeter. The first part deals with the theoretical analysis of the principles of interference and polarization of light. It further explains the basic operation of the above-mentioned devices as well as the immunity of the optical fiber to EMI. The second part of the work presents selected devices and technologies that were used as a source of electromagnetic or magnetic radiation. Subsequently, individual phenomena are plotted both in the course of time and with the help of a spectrogram or Poincaré sphere. From the measured results we can conclude that the commonly available technologies, which were selected for the diploma thesis, will not cause greater negative problems to the signal on measured frequencies in optical fibre, that could degrade the transmitted signal.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20786号 / 理博第4330号 / 新制||理||1622(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 谷森 達, 教授 永江 知文, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

No description available.

Liquid crystals are traditionally aligned via a rubbed substrate. The rubbing creates anisotropic defects and strain in the material which provide an energetically favorable orientation for the liquid crystal (LC). This is a well-developed technology that is used in virtually all liquid crystal displays (LCDs). However, it is only capable of uniform alignment on a large planar substrate. This work utilizes a new class of photoalignment materials (PM) that replace the traditional buffing technique. PMs allow for patterned LC alignment using polarized photo-lithography. Further, instead of using a nematic liquid crystal, a UV curable liquid crystal polymer (LCP) is coated on this patterned alignment material. This generates a cured, aligned, and patterned thin film that has retardance and diattenuation if a dichroic dye is incorporated in the LCP. Using these materials and methods, retarders, polarizers, and polarized fluorescent sources are fabricated with dimensions as small as a few microns. In addition to exploring the material and processing properties of the PM and LCP system, arrays of micropolarizer are fabricated for the construction of a prototype polarization camera, termed an imaging polarimeter. An imaging polarimeter is a device that measures not only the intensity but also the polarization state of a light field. My imaging polarimeter design incorporates a patterned LCP polarizer focal plane array (FPA) that is aligned and mounted to a charge-couple-device (CCD) image sensor. A polarizer FPA allows an individual pixel on a CCD sensor to detect a unique polarization state, such as a specific linear polarization orientation or right or left handed circular polarization. Neighboring pixels are designed to detect different states and each cluster can then estimate the incident polarization state. Results of a linear LCP polarimeter operating in the visible spectrum are presented.