Open AccessQuantitative investigation of linear arbitrary polarization in an APPLE‐II undulator
Author(s) -
Hand Matthew,
Wang Hongchang,
Maccherozzi Francesco,
Apollonio Marco,
Zhu Jingtao,
Dhesi Sarnjeet S.,
Sawhney Kawal
Publication year - 2018
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/s1600577518001960
Subject(s) - undulator , polarimeter , synchrotron radiation , physics , beamline , optics , linear polarization , polarization (electrochemistry) , photon , linear particle accelerator , stokes parameters , cathode ray , photon energy , beam (structure) , electron , polarimetry , laser , quantum mechanics , chemistry , scattering
Insertion devices are utilized at synchrotron radiation facilities around the world for their capability to provide a high‐brilliance X‐ray beam. APPLE‐II type undulators are especially important for their capacity to switch between a variety of photon beam polarization states. A high‐precision soft X‐ray polarimeter has been used to investigate the polarization calibration of an APPLE‐II undulator (period length λ u = 64 mm) installed on beamline I06 at Diamond Light Source. Systematic measurement of the beam polarization state at a range of linear arbitrary angles has been compared with the expected result for a given set of undulator gap and row phase parameters calculated from theory. Determination of the corresponding Stokes–Poincaré parameters from the measured data reveals a discrepancy between the two. The limited number of energy/polarization combinations included in the undulator calibration tables necessitates the use of interpolated values for the missing points which is expected to contribute to the discrepancy. However, by modifying the orbit of the electron beam through the undulator by at least 160 µm it has been found that for certain linear polarizations the discrepancies can be corrected. Overall, it is suggested that complete correction of the Stokes–Poincaré parameters for all linear angles would require alteration of both these aspects.