Open AccessInvestigation of the polarization state of dual APPLE‐II undulators
Author(s) -
Hand Matthew,
Wang Hongchang,
Dhesi Sarnjeet S.,
Sawhney Kawal
Publication year - 2016
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577515021645
Subject(s) - undulator , polarimeter , optics , physics , polarization (electrochemistry) , linear polarization , circular polarization , degree of polarization , beamline , polarization rotator , elliptical polarization , photon , stokes parameters , beam (structure) , laser , polarimetry , chemistry , birefringence , scattering , microstrip
The use of an APPLE II undulator is extremely important for providing a high‐brilliance X‐ray beam with the capability to switch between various photon beam polarization states. A high‐precision soft X‐ray polarimeter has been used to systematically investigate the polarization characteristics of the two helical APPLE II undulators installed on beamline I06 at Diamond Light Source. A simple data acquisition and processing procedure has been developed to determine the Stokes polarization parameters for light polarized at arbitrary linear angles emitted from a single undulator, and for circularly polarized light emitted from both undulators in conjunction with a single‐period undulator phasing unit. The purity of linear polarization is found to deteriorate as the polarization angle moves away from the horizontal and vertical modes. Importantly, a negative correlation between the degree of circular polarization and the photon flux has been found when the phasing unit is used.