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DOE OSTI2019

Momentum-resolved resonant inelastic soft X-ray scattering (qRIXS) endstation at the ALS

A momentum resolved resonant inelastic X-ray scattering (qRIXS) experimental station with continuously rotatable spectrometers and parallel detection is designed to operate at different beamlines at synchrotron and free electron laser (FEL) facilities. This endstation, currently located at the Advanced Light Source (ALS), has five emission ports on the experimental chamber for mounting the high-throughput modular soft X-ray spectrometers (MXS). Coupled to the rotation from the supporting hexapod, the scattered X-rays from 27.5° (forward scattering) to 152.5° (backward scattering) relative to the incident photon beam can be recorded, enabling the momentum-resolved RIXS spectroscopy. The components of this endstation are described in details, and the preliminary RIXS measurements on highly oriented pyrolytic graphite (HOPG) reveal the low energy vibronic excitations from the strong electron-phonon coupling at C K edge around σ* band. Lastly, the grating upgrade option to enhance the performance at low photon energies is presented and the potential of this spectroscopy is discussed in summary.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Modular soft x-ray spectrometer for applications in energy sciences and quantum materials

Not Available

36 MATERIALS SCIENCE↗

DOE OSTI2015

Modular Soft X-Ray Emission Spectrograph

We have been developing the Hettrick-Underwood type soft x-ray spectrograph for over a decade. This optical design uses one spherical mirror for focusing x-rays onto the CCD detector and a set of variable line-spacing gratings for energy analysis. Unlike the previous effort carried out at the ALS, what we have achieved in the current design is to incorporate the concept of modularity. The model of spectrograph is shown below. It contains three major components: the optics chamber and downstream section (detector plus driving mechanism using a swing arm pivoted at the grating location, see figure) for inside and outside order (translation stage without swing arm, not shown here). Inside order design is often used when source size is larger than the detector pixel resolution, while the outside order is used when source size is smaller than the detector pixel resolution. Irrespective to which order is selected, there is no change in the mechanism of optics chamber. The location of optics chamber relative to the source and detector can also be changed to optimize the energy resolution at target photon energy. The incident angles on mirror and gratings can be varied, in conjunction with the grating line densities, to balance the resolution and throughput. The internal components of optics chamber are also modular and changing the dimension of optics can be done by using different holders. The modularity not only greatly reduces the design and assembling effort, but also offers the cost benefit. Although the cost of this type of spectrograph is expected to be higher than XES350, it is still significant lower than the one-of-the-kind design used at every synchrotron facilities. The unique flexibility and modularity not only allows the users to tailor the design of spectrograph for the characteristic of their sources, but also to have cost down in standardizing the fabrication parts.

Hussain, Zahid↗