Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter

Abstract

The Thorium-229 isotope features a nuclear isomer state with an extremely low energy. The currently most accepted energy value, 7.8 +- 0.5 eV, was obtained from an indirect measurement using a NASA x-ray microcalorimeter with an instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic microcalorimeters with an energy resolution down to a few eV can be used to measure the isomer energy. In particular, resolving the 29.18 keV doublet in the γ-spectrum following the α-decay of Uranium-233, corresponding to the decay into the ground and isomer state, allows to measure the isomer transition energy without additional theoretical input parameters, and increase the energy accuracy. We study the possibility of resolving the 29.18 keV line as a doublet and the dependence of the attainable precision of the energy measurement on the signal and background count rates and the instrumental resolution.

32 pages, 8 figures, eq. (3) corrected

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Cited by in corpus (12)

• Direct detection of the 229Th nuclear clock transition
• Energy of the ${}^{229}$Th nuclear clock transition
• Lifetime measurement of the ${}^{229}$Th nuclear isomer
• Nuclear clocks based on resonant excitation of gamma-transitions
• X-ray pumping of the Th-229 nuclear clock isomer
• A laser excitation scheme for ${}^{229\text{m}}$Th
• The ${}^{229}$Th isomer: prospects for a nuclear optical clock
• On an attempt to optically excite the nuclear isomer in Th-229
• Towards a 229Th-based nuclear clock
• Measuring the Th-229 nuclear isomer transition with U-233 doped crystals
• Feasibility Study of Internal Conversion Electron Spectroscopy of ${}^{229m}$Th
• The concept of laser-based conversion electron Mössbauer spectroscopy for a precise energy determination of ${}^{229m}$Th