SAMOP 2023 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 20: Poster II
A 20.30: Poster
Mittwoch, 8. März 2023, 16:30–19:00, Empore Lichthof
A dedicated 2-dimensional array of metallic magnetic microcalorimeters to resolve the 29.18 keV doublet of 229Th — •A. Brunold, A. Abeln, S. Allgeier, J. Geist, D. Hengstler, A. Orlow, L. Gastaldo, A. Fleischmann, and C. Enss — Heidelberg University
The isotope 229Th has the nuclear isomer state with the lowest presently known excitation energy, which possibly allows to connect the fields of nuclear and atomic physics with the potential application as a nuclear clock. In order to excite this very narrow transition with a laser a precise knowledge of the transition energy is needed. Recently the isomer energy (8.338±0.024) eV [Kraemer et al., arXiv:2209.10276, 2022] could be precisely determined. To get additional valuable insights, we will improve our recent high-resolution measurement [Sikorsky et al., PRL 125, 2020] of the γ-spectrum following the α-decay of 233U. This decay results in excited 229Th with a nuclear state at 29.18 keV. Resolving the doublet, that results from subsequent de-excitation to the ground and isomer state, respectively, would allow an independent measurement of the isomer energy and the branching ratio of these transitions. To resolve this doublet, we develop a 2D detector array consisting of 8×8 metallic magnetic calorimeters (MMCs). MMCs are operated at millikelvin temperatures and convert the energy of a single incident γ-ray photon into a temperature pulse which is measured by a paramagnetic temperature sensor. The detector array features an active detection area of 4 mm2, a stopping power of 63.2% for 30 keV photons and an energy resolution below 3 eV (FWHM).