IMPLEMENTATION OF AN UNDULATOR BEAMLINE ON ALADDIN

The first undulator monochromator on the Aladdin storage ring has been installed and recently tested. The design and alignment of an undulator beamline presented several unique problems not normally encountered in the design of bending magnet beamlines. The primary problem is the lack of visible radiation from the undulator source when it is operated under normal conditions. In this case a temporary beamline was installed to measure the intensity of undulator light transmitted through a pinhole which could be horizontally and vertically scanned through the undulator beam. This was used to adjust the steering of the beam to be centered in the port and to do some nondispersive characterization of the undulator. This temporary line was designed to permit precision alignment of the components of the beamline according to the measured position of the full energy beam. The monochromator used on this beamline is a 6 m toroidal grating monochromator (TGM). It allows further dispersive testing of the undulator and provides dispersed undulator flux for user experiments. The beamline is identical in terms of expected reflectivity losses and grating efficiencies to two similar beamlines implemented on bending magnets. This allows direct comparison of the flux available to experimenters from undulator sources to flux from bending magnets. Initial measurements indicate that with the undulator gap set for 50 eV, at the peak of the first harmonic, the undulator beamline produces 40 times more flux than a similar beamline using a bending magnet source. © 1990.