High-Resolution Study of X-Ray Transitions in He-like Uranium Using Novel Microcalorimeter DetectorsONLINE ONLY

Helium-like ions are the simplest atomic multibody systems and their study along the isoelectronic sequence provides a unique testing ground for the interplay of the effects of correlation, relativity and quantum electrodynamics. This is in particular true for L -> K transition, which occur between the most strongly bound electron states. However, for high-Z ions with nuclear charge Z > 54, where L -> K transition energies reach up to 100 keV, there are currently no data available to challenge state-of-the-art theory [1]. In this context the recent development of metallic magnetic calorimeter (MMC) detectors is of particular importance. Their high spectral resolution of a few tens of eV FWHM at 100 keV incident photon energy in combination with a broad spectral acceptance down to a few keV will enable new types of precision x-ray studies [2].

I will report on the first application of MMC detectors for high resolution x-ray spectroscopy at the electron cooler of the low energy storage ring CRYRING@ESR at GSI, Darmstadt. Within this experiment, the x-ray emission associated with radiative recombination of cooler electrons and stored hydrogen-like uranium ions was studied. Two MMC detectors developed within the SPARC collaboration were placed under 0° and 180° with respect to the ion beam axis [3]. First results of the data analysis will be presented.

[1]  P. Beiersdorfer and G.V. Brown, Phys. Rev. A 91, 032514 (2015).
[2]  S. Kraft-Bermuth et al., Atoms 2018, 59 (2018)
[3]  P. Pfäfflein et al., Phys. Scr. 97, 114005 (2022)