The DiagOn : An undulator diagnostic for SOLEIL low energy beamlines

We present the development of an imager for the soft X-rays beamlines of synchrotron SOLEIL and the results obtained with this device. This imager, named DiagOn, is an alignment diagnostic tool intended to precisely define the emission axis of an undulator, that has been developed by SOLEIL synchrotron Detectors and Optics 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. This kind of imager is for the moment installed at four beamlines at SOLEIL, DESIRS, TEMPO, CASSIOPEE and PLEIADES. It allows for the determination of the position of the light emission axis, to align the elements of the beamline, and especially the front end diaphragms. But, furthermore, it can be used for the primary tests of the characteristics of the insertion device.