Speaker
Description
Rowland circle-based and von Hamos spectrometers are the two most popular types of x-ray emission spectrometers. From the application point of view, there are two main categories of acquisition: (i) high energy resolution fluorescence detected x-ray absorption spectroscopy (HERFD XAS) at a constant emission energy and (ii) x-ray emission spectroscopy (XES) at a constant excitation energy, and a 2D cross product of the two categories, usually called RIXS or RXES. In this talk, I present the two spectrometer types and consider their suitability for the two acquisition categories.
Next, I present our x-ray modelling tool xrt, capable of modelling synchrotron sources, complete beamlines and particular x-ray instruments. xrt also includes a GUI for building a beamline, defining output plots and setting calculation job parameters. xrt also has another GUI that renders optical elements and rays in colorful 3D scenes. We have recently added to xrt quick and accurate calculations of bent crystals, making the modelling of x-ray emission spectrometers more realistic in energy resolution and flux.
I demonstrate the modelling capabilities of xrt applied to a few spectrometer designs. I discuss in greater detail the example of our Johansson spectrometer (a Rowland circle type) built at the Balder beamline at MAX IV that uses a 2D pixelated detector. I compare the measured acceptance band with the calculated one at various angles and diffraction orders. The measured emission maps exhibit a few surprising features that I explain by the Borrmann effect – anomalous transmission through thin crystals. Finally, I demonstrate our analysis pipeline of XES data with partial on-the-fly data reduction.
