While there are many variations of an Inelastic X-ray Scattering (IXS) spectrometer, the figure of merit is often the energy resolution and the throughput. As part of the LCLS-II-HE project, the DXS team is developing a hard X-ray IXS spectrometer with a resolution of 5 meV at 11.215 keV. The spectrometer relies on a so-called post-sample-collimation scheme, and this high degree of resolution comes with stringent precision and stability requirements. SHADOWOui is used to simulate the setup and analyze the tolerance of 4 optics’ axis (translation, pitch, yaw, roll) and the miscut angle of the channel-cut crystal of the design. The simulation indicates that a 5 meV resolution is achievable by ensuring stringent pitch and vertical translation tolerances. Furthermore, the simulation suggests that a miscut angle of 77 degrees, which necessitates high-quality crystal manufacturing, is optimal.
The Linac Coherent Light Source (LCLS) is being upgraded to the high repetition rate (up to 1 MHz) mode using cryogenic modules. As the key optical element at the X-ray Pump-probe (XPP) beamline, the goal of the large offset double-crystal monochromator (LODCM) for the High Energy (HE) upgrade is to maintain its x-ray beam multiplexing capability at higher average beam power (up to 200W) for the whole hard x-ray operating range of 6-25 keV. The upgraded LODCM system will use an upstream diamond transmission grating to achieve high power beam multiplexing. It will enable the 0th order 'transmission’ from the grating to pass through the XPP hutch. The +1st order beam, which contains about 20% power of the incident beam of the grating, will be monochromatized at the 1st crystal position, then directed to XPP experiments at the 2nd crystal position. Both crystal positions will provide 111 and 220 Si crystals. The 1 st crystals need to be cooled by Liquide Nitrogen to minimize their thermal deformation under heat load. The second crystals will be controlled close to ambient temperature. The temperature difference between the two crystals leads to a lattice constant mismatch. The corresponding difference in Bragg angles is utilized to compensate the angle between the 1 st order beam and 0th order beam (initial beam propagation axis) from the grating splitter, making it possible to maintain the propagation direction of the monochromatized beam exiting the LODCM parallel to the 0th order incoming beam.
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.
The ability to split femtosecond free electron laser pulses and recombine them with a precisely adjustable delay has numerous scientific applications such as X-ray Photon Correlation Spectroscopy and X-ray pump X-ray probe measurements. A wavefront-splitting based hard X-ray split-delay system is currently under development at the Linac Coherent Light Source. The design configuration uses a series of Si(220) crystal reflections in the horizontal scattering geometry. It covers an energy range between 6.5 and 13 keV, a delay range from -30 ps up to 500 ps at 8 keV. The design features two planar air bearing based linear stage delay lines for improved stability and accuracy during the delay adjustments in order to maintain spatial overlap of the two branches during a delay scan. We present the basic design concept, tolerance analysis, and estimated performance of the system.
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