A variable-included-angle plane-grating-monochromator on an undulator for spectroscopy and microscopy at the Advanced Light Source

A new beam line (beam line 11.0) at the Advanced Light Source has been designed to employ an SX700 (Peterson, Opt. Commun. 40 (1982) 402) style variable-included-angle plane-grating-monochromator. The extended range available from a specific grating is exploited to cover energies from the carbon 1 s absorption edge to the oxygen 1 s absorption edge with two different gratings (150 and 1200 lines/mm) with dispersion different by a factor of three. The phase space of a zone plate microscope can then be efficiently filled either at low or high resolution (R=2500 and 7500). At the same time the monochromator is designed to cover the energy range from 75 to 1500 eV using the same two gratings at high resolution for spectroscopy. A deformable mirror pair will re-focus to a monochromatic spot 5×10 μm, matched into the acceptance of a fluorescence spectrometer. The monochromator will operate in vertically collimated light and the free choice of focussing parameter provides a guarantee of high resolution even when the power loading is high. However, we will provide a thermally engineered pre-mirror so that the high resolution requirement at low photon energy can be met without loss of efficiency.