Speaker
Description
The Heisenberg-RIXS spectrometer (hRIXS) at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL is dedicated to performing resonant inelastic X-ray scattering (RIXS) measurements in the time domain, with time and energy resolution approaching the Heisenberg limit imposed by the uncertainty relations [1, 2]. The spectrometer uses a dispersive element and requires a detector with a position resolution in the order of 5 μm along the spectroscopic dimension capable of detecting photons with energies below 1 keV. Furthermore, a high frame rate capability is necessary, in order to exploit the timing structure of the European XFEL, which provides pulse trains at 10 Hz with individual X-ray pulses delivered at rates of up to 4.5 MHz.
A promising candidate is a prototype hybrid pixel detector, developed in a collaboration between the Paul Scherrer Institute (PSI) and Fondazione Bruno Kessler (FBK), which employs X-ray-sensitive inverse Low Gain Avalanche Diode (iLGAD) sensors. They are read out by the widely adopted charge-integrating application-specific integrated circuit (ASIC) JUNGFRAU [3, 4]. The iLGAD sensor has a total size of 4×4 cm$^2$ and is segmented into rectangular pixels with a size of 25×225 μm$^2$, offering a high resolution along the dispersion direction. In order to achieve the required spatial resolution, photon-hit-position finding algorithms exploiting charge-sharing are investigated. Currently different approaches for event classification are considered, based either on component identification using a second threshold or evaluating a neighbourhood of predefined shape. Their performance for position determination with sub-pixel resolution is studied. Furthermore, a focus lies on evaluating their suitability and robustness in an automated data analysis framework, i.e., needing minimal expert intervention, in order to be employed in routine user operation. We will report on the status of the investigation including preliminary results from a slanted-edge measurement.
[1] Van den Brink, Jeroen. "Resonant inelastic x-ray scattering on elementary excitations." Rev. Mod. Phys 83 (2011): 705.
[2] Schlappa, Justine, et al. "The Heisenberg-RIXS instrument at the European XFEL." Synchrotron Radiation 32.1 (2025).
[3] Mozzanica, A., et al. "The JUNGFRAU detector for applications at synchrotron light sources and XFELs." Synchrotron Radiation News 31.6 (2018): 16-20.
[4] Hinger, Viktoria, et al. "Resolving soft X-ray photons with a high-rate hybrid pixel detector." Frontiers in Physics 12 (2024): 1352134
The authors acknowledge funding from the Swiss National Science Foundation (SNSF) [PZ00P2_223377]. For the purpose of open access, a CC BY public copyright license is applied to any author accepted manuscript (AAM) version arising from this submission.