@thesis{wojtaczka_towards_2025,
	title = {Towards efficient terbium extraction: molecular beams of {TbFx} for {ISOL} and nuclear medicine},
	url = {https://zenodo.org/records/18086803},
	doi = {10.5281/zenodo.18086803},
	shorttitle = {Towards efficient terbium extraction},
	abstract = {The production of radioactive ion beams ({RIBs}) of terbium (Tb) is of growing interest for both fundamental nuclear-physics studies and nuclear-medicine applications. Four of its radioisotopes, Tb-149, Tb-152, Tb-155 and Tb-161, show particular promise for molecular imagining and targeted cancer therapies, enabling a true theragnostic approach. However, the production of these isotopes, aside from reactor-produced Tb-161, remains challenging, with current methods unable to meet the demands of sustained preclinical research. Among existing methods, the Isotope Separation On-Line ({ISOL}) technique is currently the only one capable of producing samples of Tb-149, Tb-152 and Tb-155 with high enough radioisotopic purity for development of terbium-based radiopharmaceuticals.

The direct extraction of terbium from irradiated tantalum targets at {ISOL} facilities is hindered by terbium’s low volatility and strong surface adsorption to tantalum. These properties render it "sticky" and lead to poor extraction efficiencies. Consequently, current approaches rely on indirect production routes, such as the extraction of laser ionised precursor dysprosium (Dy), limiting the fundamental research on exotic terbium isotopes and the translation of protocols for offline mass separation. 

This thesis addresses the bottleneck in terbium production by exploring molecular extraction of‘ terbium as a strategy to enhance its volatility and production efficiency. The development of isotope extraction via molecular sidebands offers a promising pathway to access non-volatile elements, such as terbium, that are otherwise difficult to extract directly from the target. Building on the advances in molecular extraction of actinides, in this work terbium fluoride behaviour is systematically investigated using a combination of online and offline studies. A series of experiments were conducted at five different mass separators at {CERN} associated with the {CERN}-{ISOLDE} facility, including {CERN}-{MEDICIS}. The initial investigation was performed using stable compounds at {ISOLDE}’s offline facilities under simulated {ISOL} conditions to establish the behaviour of the molecules in the extreme conditions of the {ISOL} method. Subsequent experiments using irradiated tantalum targets and {FEBIAD}-type ion sources, with {CF}4 injection to promote fluoride formation, examined terbium release as a function of different experimental parameters. The ion beams were analysed using Multi Reflection Time-of-Flight Mass Spectrometry ({MR}-{ToF} {MS}), supported by gamma and alpha spectrometry.

This thesis demonstrates the feasibility of extracting terbium as its molecular sidebands, providing insights into best operating conditions and underlying physical mechanisms. It also highlights the limitations of this method and other current production routes. Moreover, it offers a benchmark for extending molecular extraction to other lanthanides of interest. The findings not only enhance our understanding of terbium and terbium fluoride chemistry in extreme {ISOL} conditions but also provides a pathway for future work. Aside from answers, this thesis also raises questions on what’s the best way forward.

The future of large-scale terbium isotope production lies in the optimisation of extraction techniques which can be applied at emerging facilities such as {ISOL}@{MYRRHA} and {TATTOOS}@{PSI}. The presented work is a part of ongoing effort to optimise production of terbium radionuclides for clinical and preclinical applications, necessary for advancements in nuclear medicine.},
	type = {phdthesis},
	author = {Wojtaczka, Wiktoria},
	urldate = {2026-01-05},
	date = {2025-09-01},
	keywords = {ion sources, radioactive ion beams, radioactive molecules, thesis},
}