Search results for "Polarimeter"
showing 10 items of 35 documents
Development of hard x-ray photoelectron SPLEED-based spectrometer applicable for probing of buried magnetic layer valence states
2016
Abstract A novel design of high-voltage compatible polarimeter for spin-resolved hard X-ray photoelectron spectroscopy (Spin-HAXPES) went into operation at beamline BL09XU of SPring-8 in Hyogo, Japan. The detector is based on the well-established principle of electron diffraction from a W(001) single-crystal at a scattering energy of 103.5 eV. It's special feature is that it can be operated at a high negative bias potential up to 10 kV, necessary to access the HAXPES range. The polarimeter is operated behind a large hemispherical analyzer (Scienta R-4000). It was optimized for high transmission of the transfer optics. A delay-line detector (20 mm dia.) is positioned at the exit plane of the…
Vertical Beam Polarization at MAMI
2017
For the first time a vertically polarized electron beam has been used for physics experiments at MAMI in the energy range between 180 and 855 MeV. The beam-normal single-spin asymmetry $A_{\mathrm{n}}$, which is a direct probe of higher-order photon exchange beyond the first Born approximation, has been measured in the reaction $^{12}\mathrm C(\vec e,e')^{12}\mathrm C$. Vertical polarization orientation was necessary to measure this asymmetry with the existing experimental setup. In this paper we describe the procedure to orient the electron polarization vector vertically, and the concept of determining both its magnitude and orientation with the available setup. A sophisticated method has …
The Second Flight of the Sunrise Balloon-borne Solar Observatory: Overview of Instrument Updates, the Flight, the Data, and First Results
2017
S. K. Solanki et. al.
Imaging spin filter for electrons based on specular reflection from iridium (001)
2013
Abstract As Stern–Gerlach type spin filters do not work with electrons, spin analysis of electron beams is accomplished by spin-dependent scattering processes based on spin–orbit or exchange interaction. Existing polarimeters are single-channel devices characterized by an inherently low figure of merit (FoM) of typically 10 −4 –10 −3 . This single-channel approach is not compatible with parallel imaging microscopes and also not with modern electron spectrometers that acquire a certain energy and angular interval simultaneously. We present a novel type of polarimeter that can transport a full image by making use of k -parallel conservation in low-energy electron diffraction. We studied specul…
First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO
2005
The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developped a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting de…
Computer aided photoelasticity by an optimum phase stepping method
2002
In this paper an automated photoelastic method based on the phase stepping technique is described. It provides full-field maps of the isoclinic parameter and the relative retardation. The technique is based on processing six images of a photoelastic specimen acquired using plane and circularly polarized light. The number of acquisitions and the type of polariscope used in this approach have been chosen with the aim at reducing the influence of quarter wave plate errors and obtaining raw photoelastic data in a periodic form suitable for easy applications of automatic unwrapping routines.
Spin-polarized photoelectrons resonantly excited by circularly polarized light from a fractional Ag film on GaAs(100)
2013
We demonstrate a finite spin polarization of photoelectrons emitted from GaAs(100) covered by a fractional Ag film. The photoemission yield shows a sharp maximum for intermediate coverage and the spin polarization increases with increasing laser intensity. Photoelectrons are excited by circularly polarized 100 fs laser pulses of 800 nm wavelength. We recorded the photoemitted electrons using a photoemission electron microscope combined with a Mott spin polarimeter. The spin polarization is analyzed in dependence on the excitation frequency and intensity and on the average thickness of the silver film. The results are explained by a model combining multiphoton photoemission and optical field…
Scattering and Depolarization in a Polymer Dispersed Liquid Crystal Cell
2008
An imaging polarimeter in transmission has been used to explore the effects of scatter and depolarization induced by a polymer dispersed liquid crystal cell. The experiment was carried out for three visible wavelengths. Both a directional and a scattered component can be distinguished in the light transmitted by this material. Whereas the directional component increased with voltage, the scattered portion decreased. This was a common behaviour for all three wavelengths. The polarimetric analysis revealed that the degree of polarization was also affected by changes in the voltage applied to the cell. Depolarization effects in the scattered component were usually high and decreased with volta…
Measurement of high energy resolution inelastic proton scattering at and close to zero degrees
2009
13 pages, 15 figures.-- Printed version published Jul 1, 2009.
The BLAST experiment
2009
The Bates large acceptance spectrometer toroid (BLAST) experiment was operated at the MIT-Bates Linear Accelerator Center from 2003 until 2005. The detector and experimental program were designed to study, in a systematic manner, the spin-dependent electromagnetic interaction in few-nucleon systems. As such the data will provide improved measurements for neutron, proton, and deuteron form factors. The data will also allow details of the reaction mechanism, such as the role of final state interactions, pion production, and resonances to be studied. The experiment used: a longitudinally polarized electron beam stored in the South Hall Storage Ring; a highly polarized, isotopically pure, inter…