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The nanoscience beamline at Diamond, optical design considerations

DOI: 10.1063/1.2436124 DOI Help

Authors: Ruben Reininger (Scientific Answers & Solutions) , Sarnjeet Dhesi (Diamond Light Source)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: Ninth International Conference on Synchrotron Radiation Instrumentation
Peer Reviewed: No

State: Published (Approved)
Published: June 2007

Abstract: The main requirement of the Nanoscience Beamline at Diamond is to deliver the highest possible flux at the sample position of a PEEM with a resolving power of about 5000 in the energy range 80–2000 eV. The source of the beamline is a couple of APPLE II helical undulators in tandem that can also be used separately to allow for faster switching of the circular polarization. Based on its versatility, a collimated plane grating monochromator using sagittally focusing elements was chosen to cover the required energy range with three gratings. The operation of this monochromator requires a collimated beam incident on the grating along the dispersion direction. This can be achieved either with a toroid, focusing with its major radius along the non‐dispersive direction at the exit slit, or with a sagittal cylinder. The former option uses a sagittal cylinder after the grating to focus the collimated beam at the exit slit. In the latter case, a toroid after the grating is used to focus in both directions at the exit slit. The advantage of the toroid downstream the grating is the higher horizontal demagnification. This configuration fulfills the Nanoscience Beamline’s required resolving power but cannot be used to achieve very high resolution due to the astigmatic coma aberration of the toroidal mirror. The focusing at the sample position is performed with a KB pair of plane elliptical mirrors. Assuming achievable values for the errors on all the optical surfaces, the expected spots FWHW in the horizontal and vertical directions are 10 μm and 3 μm, respectively. The calculated photon flux at this spot at 5000 resolving power is >1012 photons/sec between 80 and 1600 eV for linearly polarized light and between 106 and 1200 eV for circularly polarized light. The beamline is expected to be operational in January 2007.

Journal Keywords: Beam Production; Design; Diffraction Gratings; Emission Spectroscopy; Ev Range; Mirrors; Monochromators; Nanostructures; Operation; Photoelectron Spectroscopy; Photon Beams; Polarization; Polarized Beams; Resolution; Wiggler Magnets; X Radiation

Subject Areas: Engineering, Physics

Technical Areas: Accelerator Physics

Added On: 29/02/2016 13:33

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Physics Engineering & Technology

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