$\bf{^{229}}$Th reloaded: Determining the isomer energy with metallic magnetic calorimeters

26 Jul 2019, 10:30
15m
Auditorium G. Testori (Milano)

Auditorium G. Testori

Milano

Piazza Città di Lombardia, 1, 20124 Milano MI
Oral Presentation Low Temperature Detector Applications Orals LM 004

Speaker

Jeschua Geist (Kirchhoff Institute for Physics, Heidelberg University)

Description

The isotope $^{229}$Th has the 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 reduce the uncertainty of the currently most accepted value for this isomer energy, $(7.8\pm0.5)\,\mathrm{eV}$, we measure the $\gamma$-spectrum following the $\alpha$-decay of $^{233}$U and derive the isomer energy in three different ways from the acquired high-resolution $\gamma$-spectrum.

We present the detector array maXs-30 consisting of $8\times8$ metallic magnetic calorimeters, providing a quantum-efficiency of about 65% at $29\,$keV, an instrumental resolution below $10\,$eV$_{\rm FWHM}$ and a large detection area of $4\,\mathrm{mm}\times 4\,\mathrm{mm}$ to face the low rate of the $29.18\,\mathrm{keV}$ transitions. Due to this low flux of relevant photons, the experiment was benefiting greatly from the small and thermodynamically well understood non-linearity and the straight-forward co-addibility of spectra taken at different times with different pixels.

We show latest $^{229}$Th spectra and discuss the results of the different ways to derive the isomer energy from these spectra, suggesting a new value for the isomer energy, which is about $0.5\,$eV higher than the currently most accepted one.

Student (Ph.D., M.Sc. or B.Sc.) Y
Less than 5 years of experience since completion of Ph.D N

Primary author

Jeschua Geist (Kirchhoff Institute for Physics, Heidelberg University)

Co-authors

Jürgen Bussmann (Kirchhoff Institute for Physics, Heidelberg University) Daniel Hengstler (Kirchhoff Institute for Physics, Heidelberg University) Rebecca Pons (Kirchhoff Institute for Physics, Heidelberg University) Philip Schneider (Kirchhoff Institute for Physics, Heidelberg University) Loredana Gastaldo (Kirchhoff Institute for Physics, Heidelberg University) Andreas Fleischmann (Kirchhoff Institute for Physics, Heidelberg University) Sebastian Kempf (Kirchhoff Institute for Physics, Heidelberg University) Christian Enss (Kirchhoff Institute for Physics, Heidelberg University) Kjelt Beeks (Institute for Atomic and Subatomic Physics, TU Wien) Georgy Kazakov (Institute for Atomic and Subatomic Physics, TU Wien) Tomas Sikorsky (Institute for Atomic and Subatomic Physics, TU Wien) Thorsten Schumm (Institute for Atomic and Subatomic Physics, TU Wien) Christoph Mokry (Institute of Nuclear Chemistry, Johannes Gutenberg University Mainz) Jörg Runke (Institute of Nuclear Chemistry, Johannes Gutenberg University Mainz) Christoph E. Düllmann (Johannes Gutenberg University Mainz)

Presentation Materials