RaDTho · Radiative Decay Study of the low-lying thorium-229 isomer
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2021-08-01 → 2023-07-31
- EU contribution
- €166,320
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Radiative Decay Study of the low-lying thorium-229 isomer
The radionuclide thorium-229 features an extremely low exciation siomer with an energy of around 8 eV. This unique low-lying isomer features an expected radiative lifetime as high as 10000 s. This results in a a very narrow linewidth of this transition. The possibility of a direct exciation of this nuclear transition with a vacuum-ultraviolet (VUV) laser and the robustness of nuclear transitions to the environmental conditions makes this isomer of thorium-229 a possible building block of a new frequency standard - a nuclear clock. Such nuclear clocks could match, or even exceed the precision of the current stat-of-the-art optical clocks and will provide an excillent tool for the test of fundamental physics. This project aims to characterize this special nuclear isomer and has two main objectives: 1. Radioactive ion beams of mass A=229, consisting of francium and radium, are implanted into a large band-gap solid state crystals such as calcium fluoride and magnesium fluoride at the ISOLDE flacility in CERN. These implanted crystals are placed in a VUV-spectrometer and the potons stemming from the decay of the isomer are wavelength selected giving a precise energy measurement of the isomer. Such a spectrometer enables the measurement of the excitation energy of the isomer by directly detecting the photons stemming from the isomer's radiative decay. Following the VUV-signal over time the radiative livetime of the isomer will be measured. 2. To measure the hyperfine structure of the singly charged thoirum-229 isomer and ground state to extract the magnetic dipole moment and the electric quadrupole moment using the in-gas-jet spectroscopy setup at KU Leuven.
Data: CORDIS, © European Union
Project objective
The existence of a low-lying nuclear isomer of thorium-229 at 8.28 eV was suggested several decades ago but was only recently identified via the observation of its decay signal. The low energy and an estimated relative decay width of around 10^{-19} open new possibilities for the development of a nuclear frequency standard-a nuclear clock, which can outperform the existing atomic clocks. This will have far-reaching consequences, such as in metrology, dark matter research, geodesy and time variation of fundamental constants. However, the isomer's properties are unknown or known with insufficient accuracy to exploit its far-reaching opportunities. This proposal aims to determine the properties of the isomer using two complementary techniques.1. The isomer is populated using a novel mechanism via the beta-decay of actinium-229 implanted in a suitable crystal at the ISOLDE-CERN facility. VUV spectrometry of the implanted crystal will allow measurement of the isomer's excitation energy with a precision of < 0.1 nm as well as its radiative-decay half-life. This production scheme increases the sensitivity by at least a factor of five and allows for improved control of experimental conditions and a reduced background signal.2. Magnetic dipole and electric quadrupole moment as well as the nuclear charge radii of the singly charged ground state and isomer of thorium-229, produced via alpha-decay of uranium-233, will be measured using the in-gas-jet laser ionization and spectroscopy technique at KU Leuven. This technique allows the necessary efficiency, sensitivity and spectral resolution to measure the hyperfine structure of the singly charged thorium-229 ground state and isomer.
Original text from CORDIS.
Participants
- KATHOLIEKE UNIVERSITEIT LEUVEN · LeuvenCoordinatorBelgium
Links
Data: CORDIS, © European Union