Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 63: Precision Spectroscopy of Atoms and Ions V (joint session A/Q)

Q 63.4: Talk

Thursday, March 5, 2026, 15:15–15:30, N 3

MMC Array to Study X-ray Transitions in Muonic Atoms — •Hendrik Hadenfeldt for the QUARTET collaboration — Kirchhoff-Institute for Physics, Heidelberg University, Germany

The QUARTET collaboration aims to improve the accuracy of absolute nuclear charge radii of light nuclei from Li to Ne using high-precision X-ray spectroscopy of muonic atoms. A measurement with isotopically pure oxygen and copper has recently been performed at the Paul-Scherrer-Institute (PSI). Conventional solid-state detectors do not provide sufficient accuracy in the relevant energy range around 120 keV. Therefore, we use a low-temperature Metallic Magnetic Calorimeter (MMC). MMCs are characterized by a high resolving power of several thousand and a high quantum efficiency for the energy range of interest using 100 µm thick absorbers. In this talk, we present a newly developed MMC detector. First preliminary spectra and systematic effects observed in the measurement are discussed. The acquired data, together with the achieved energy resolution of better than 50 eV FWHM at 120 keV, enable a more precise characterization of muonic X-ray lines. In addition, we present the world’s first compositional study of a prehistoric human tooth using high-precision X-ray spectroscopy of muonic atoms.

Keywords: Metallic magnetic calorimeter; X-ray spectroscopy; Muonic atoms; Absolute nuclear charge radii; QUARTET