In order to to achieve high spatial resolution and maximise collection efficiency, the beamline was designed to convey the highest possible flux density at the microscope focus. Target requirements were met by combining an insertion device with a moderate energy resolving power monochromator, together with microspot refocussing of the photon beam. Given the typical working conditions of the microscope (2 μm to 5 μm field of view), the beamline strongly demagnifies the source, providing homogeneous illumination of the sample area which is imaged by the microscope.
The Nanospectroscopy beamline shares the insertion device with the Elettra Free Electron Laser (EuFEL). Based on the Sasaki Apple II scheme, it consists of two identical undulator sections (Elettra insertion devices 1.1 and 1.2) together with a phase modulation electromagnet. The insertion device is able to provide elliptically polarised light (circular left and right as well as linear horizontal and vertical as special cases) in a spectral range extending from 50 eV to 1000 eV, with high brilliance (using the first, third and fifth undulator harmonic). We emphasise the undulator capability of helicity inversion, which allows performing XMCD (X-Ray Magnetic Circular Dichroism) measurements.
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