Periodic Reporting for period 1 - RaDTho (Radiative Decay Study of the low-lying thorium-229 isomer)
Periodo di rendicontazione: 2021-08-01 al 2023-07-31
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.
Improvements in the VUV-spectrometer as well as the data acquisition system was performed after the IS658 measurements at ISOLDE. To improve the precision of the isomer's excitation energy, new optimized calibration method and experimental procedures were developed to minimize the systematic uncertainty. Another experiment campaign IS715 was performed in July, 2023, end of the fellowship period. Several different crystals were tested during this experiment campaign and the VUV-efficiency and the isomer' lifetime have been measured in different crystals.
The second part of this project was the measurement of the hyperfine structure of the isomer and the ground state of a singly charged thorium-229 ion. An important first step for this part was a develpment of an efficient ionization scheme. Due to the lack of such efficient ionization scheme, this part of the project was delayed in order to search for an efficient ionization shcme and to measure the second ionization potential of thorium-229. A more efficient ionization scheme has been developed and the measurements for the second ionization potential is still ongoing.