Speaker
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 |
