The DiagOn: an Undulator Diagnostic for SOLEIL Low Energy Beamlines

DiagOn is a diagnostic tool intended to precisely define the emission axis of an undulator, that has been developed by SOLEIL synchrotron Optics and Detectors groups. It uses the particular structure of monochromatic undulator emission into a narrow hollow cone centered on the axis. One wavelength is selected by a multilayer mirror to produce a characteristic image of the emission cone on scintillator and CCD camera. We review the emission properties of undulator in order to define the best parameters, K value, photon energy and emission angle, for diagnosis. Then the choice of optimal multilayer coating of the mirror is discussed. We finish by some consideration on mirror cooling and mechanical conception for stable operation. The precise localization of the undulator axis will allow an optimal and fast alignment of the elements located before this detector, particularly adjustable aperture from the head of each of the lines.