Rostock 2019 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 18: Precision Spectroscopy of atoms and ions V (Th 229)

A 18.5: Vortrag

Mittwoch, 13. März 2019, 15:00–15:15, S HS 2 Physik

Gamma spectroscopy to measure the ²²⁹Th isomer energy using a 2-dimensional array of metallic magnetic microcalorimeters — •Jeschua Geist¹, Daniel Hengstler¹, Christian Schötz¹, Sebastian Kempf¹, Loredana Gastaldo¹, Andreas Fleischmann¹, Christian Enss¹, Georgy A. Kazakov², Simon Stellmer², and Thorsten Schumm² — ¹Heidelberg University — ²Vienna University of Technology

The isotope ²²⁹Th has a nuclear isomer state with the lowest presently known excitation energy, which possibly allows to connect the fields of nuclear and atomic physic with a potential application in a nuclear clock. In order to verify and improve the accuracy of the currently most accepted energy value for this isomere energy, (7.8±0.5) eV, we plan to resolve the 29.18 keV doublet in the γ-spectrum following the α-decay of ²³³U, corresponding to the decay into the ground and isomer state, to measure the isomer transition energy without additional theoretical input parameters.

We developed the detector array maXs-30 consisting of 8x8 metallic magnetic calorimeters with an expected energy resolution below 6 eV, providing a large detection area of 16 mm² to face the low rate of the 29.18 keV transitions. We present a new value for the isomere energy with a detector performance of 11 eV FWHM for photons up to 60 keV, show latest recorded ²²⁹Th spectra and discuss different ways to derive the isomer energy from these spectra.