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The Linac Coherent Light Source (LCLS) of SLAC is upgrading the facility to a more flexible design, permitting both, high energy per pulse mode and High Repetition Rate mode. Two independent “sources” Soft and Hard X-ray will serve five of the existing beamlines and three completely new ones.
We will present here, one of the new beamlines, mainly dedicated to Resonant Inelastic Scattering (RIXS) and Liquid Jet based experiments.
The beamline is designed to deliver the beam to the floor upstairs of the existing experimental area by using a large deflection, grating based monochromator. The monochromator is designed to provide both, very high resolving power (E/ΔE<50,000) and transform limited low-resolution mode. To accommodate those very different operative modes, the footprint of the beam on the gratings is controlled to illuminate the proper amount of lines. An elliptical bendable mirror, in front of the monochromator, will create four different virtual sources, to cover the photon energy range from 250 to 1600 eV in both modes.
After the monochromator, the beamline will serve three experimental stations installed in line. A pair of plan elliptical bendable mirrors, operating in the Kirkpatrick-Baez configuration, will focus the radiation in the proper experimental station. The focal spot size, will be controllable, permitting to adapt it to the need of the experiment. Another major requirement is to preserve the uniformity of the beam, out of focus, with a maximum intensity variation of less than 5%. This implies maintaining the shape error of all the optics to sub-nm levels, even in the presence of heat load. The design principle and performance of the three active mirrors and the impact on the monochromator and spot profile will be presented in details, together with some preliminary tests.
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