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Te use of radioactive molecules for fundamental physics research is a developing interdisciplinary field limited dominantly by their scarce availability. In this work, radioactive molecular ion beams containing actinide nuclei extracted from uranium carbide targets are produced via the Isotope Separation On-Line technique at the CERN-ISOLDE facility. Two methods of molecular beam production are studied: extraction of molecular ion beams from the ion source, and formation of molecular ions from the mass-separated ion beam in a gas-filled radio-frequency quadrupole ion trap. Ion currents of U+, UO1−3+, UC1−3+, UF1−4+, UF1,2O1,2+are reported. Metastable tantalum and uranium fluoride molecular ions are identified. Formation of UO1−3+, U(OH)1−3+, UC1−3+, UF1,2O1,2+from mass-separated beams of U+, UF1,2+with residual gas is observed in the ion trap. The effect of trapping time on molecular formation is presented.

ISOLDE’s Offline 2 laboratory has been upgraded to facilitate development for the production and study of molecular ion beams. New gas injection systems have been implemented for both molecular formation in the ion source and in the radio-frequency quadrupole ion trap used for beam preparation. MagneToF detectors and time-resolved single ion counting data acquisition have been implemented for low intensity beams and studies of laser-atom or laser-molecule interactions. We present a study of the formation and ionization of BaF+using the upgraded facility.

Relativistic coupled-cluster calculations of the ionization potential, dissociation energy, and excited electronic states under 35,000 cm$^{-1}$ are presented for the actinium monofluoride (AcF) molecule. The ionization potential is calculated to be IP$_e=48,866$ cm$^{-1}$, and the ground state is confirmed to be a closed-shell singlet and thus strongly sensitive to the $\mathcal{T}$,$\mathcal{P}$-violating nuclear Schiff moment of the Ac nucleus. Radiative properties and transition dipole moments from the ground state are identified for several excited states, achieving an uncertainty of $\sim$450 cm$^{-1}$ for the excitation energies. For higher-lying states that are not directly accessible from the ground state, possible two-step excitation pathways are proposed. The calculated branching ratios and Franck-Condon factors are used to investigate the suitability of AcF for direct laser cooling. The lifetime of the metastable $(1)^3\Delta_1$ state, which can be used in experimental searches of the electric dipole moment of the electron, is estimated to be of order 1 ms.

Thursday 14 April 2022 Contribution X-O41 Chair: E. Colineau

Contribution ID:57 Type:Invited Tuesday, December 14, 2021 2:40 PM (15 minutes)

The method of Isotope Separation On-Line (ISOL) is one of the most successful ways to produce rare nuclei. Hitting a target material with accelerated particles generates heat and reaction products which then diffuse and effuse through the target material before they are released for ionization and extraction for experiments in nuclear physics, astrophysics, materials science, pharmaceuticals, and many more. The target material temperature dominates the release process and is limiting the primary beam intensity. Heat is dissipated from the beam spot through the target material, making the effective thermal conductivity of the target material critical for the ISOL process. Specifically-engineered microstructures have the potential to achieve better release properties. To address the thermal challenges in target materials, a deeper understanding of the thermal conductivity of these engineered materials is required. In this work, a numerical method is developed for evaluating the effective thermal conductivity of representative microstructures. A combined parallel and series model agrees with numerical data of four representative microstructures when thermal radiation through pores is considered by fitting a morphological parameter and a parameter describing the portion of series connections. Separately, a steady-state experimental-numerical method is used to determine the effective thermal conductivity of porous β-SiC slip-cast material and β-SiC pressed pellet material as a function of temperature up to 1200˚C and 1050˚C respectively. In addition, a new experimental apparatus for effective thermal conductivity is presented from conceptual design to operation. This thesis works towards understanding thermal transport through target materials. The new numerical method for material analysis, effective thermal conductivity measurements on SiC, and the establishment of the CHI system at TRIUMF for thermal conductivity measurements on target materials help build towards systematic studies of engineered materials in ISOL and beyond.