A spherical grating monochromator and beamline optimised for the provision of polarised synchrotron radiation in the photon energy range 20–200 eV

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 184; no. 4; pp. 627 - 643
• Main Authors: Finetti, P, Holland, D.M.P, Latimer, C.J, Binns, C, Quinn, F.M, Bowler, M.A, Grant, A.F, Mythen, C.S
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2001
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(01)00818-7

The design and performance of a spherical grating monochromator and beamline optimised for experiments requiring polarised radiation are described. The beamline is mounted on a bending magnet source at the Synchrotron Radiation Source at Daresbury Laboratory, and the monochromator incorporates three gratings to cover the photon energy range 20–200 eV. The relative first- and higher-order grating efficiencies have been measured by means of photoelectron spectroscopy and have been compared to theoretical predictions. A movable aperture, placed in the optical path between the source and the first mirror, defines the photon emission directions of the beam entering the beamline. The polarisation of the radiation leaving the beamline is determined both by the vertical position of this aperture and by the modifications introduced by the beamline geometry and the optical components. The modification to the polarisation is difficult to calculate analytically, and a satisfactory quantitative assessment can only be accomplished through a combination of reflectivity and ray-tracing analysis. A reflection polarimeter has been used to obtain a full characterisation of the polarisation in the energy range 20–40 eV. These measurements have enabled the Stokes parameters to be deduced. The degree of linear polarisation has also been investigated through angle resolved photoelectron spectroscopy measurements.