The BL24 (CIRCE)is a photoemission spectroscopy and microscopy beamline with a helical undulator providing variable-polarization soft X-rays. It has two advanced experimental end-stations for the characterization of surfaces, thin films and nanostructures. One of the end-stations is a Photoemission Electron Microscope (PEEM), also equipped with an electron gun for Low-Energy Electron Microscopy (LEEM) and an electron energy analyzer. This instrument permits a variety of chemical, morphological and magnetic imaging techniques fully adapted to the field of nanotechnology.

The other end-station is for Near Ambient Pressure Photoemission (NAPP). With this instrument it is possible to perform X-ray photoemission spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS or XANES) on samples in gas or vapor atmosphere up to 10 mbar. The research focus is the characterization of samples in areas such as catalytic processes, wetting, environmental sciences and surface science, where gas/solid or gas/liquid interactions play an important role. Both experimental stations have facilities for in situ sample preparation (metal evaporators, gas exposure, heating, cooling, etc.).