Speaker
Description
High-fluence isotope implantation using magnetic mass separation has become a critical technique across various research fields. For example, in medical isotope production, one of the key research areas is the purification of these radionuclides through mass separation followed by implantation. Additionally, mass-separated, implanted targets are used for nuclear charge radius determination through muonic x-ray spectroscopy where isotopic purity is critical [1]. Again, high-fluence isotope implantations are necessary to obtain the required targets ($\approx 5 \mu$g implanted on a few cm$^2$). Also, for neutron time-of-flight studies and beyond standard model searches with molecules, high-fluence isotope implantations are a key aspect [2].
Recently, at CERN-MEDICIS, through online monitoring of the incoming activity, it has been observed that a significant fraction of the activity (up to 74%) of the incoming isotopes remained in the collection chamber after removing the collection substrate [3]. Similarly, for muonic x-ray spectroscopy targets, significant discrepancies were observed between the incoming fluence and the retained fluence in the foil (up to 84%) [1]. It was suggested that these losses are caused by self-sputtering. Self-sputtering occurs when the primary beam can remove a sufficient number of substrate particles such that, eventually, the earlier implanted nuclei of the species of interest can be removed from the implantation substrate as well.
In this contribution, we will present the results of our investigations into self-sputtering, focusing on two primary aspects: firstly, a framework was developed to guide future (medical) isotope collections based on TRIDYN [4,5], which is a Monte-Carlo-based simulation software package that allows for dynamical changes of the target.
Secondly, the TRIDYN simulations were compared to experimental implantation of Yb into Al and Zn.
The results provide essential information for improving the collection efficiency. This is crucial to overcome the fundamental limits imposed by self-sputtering, for example to scale up medical isotope production, at CERN MEDICIS today, but also at new facilities such as ISOLpharm at SPES, ISOL@MYRRHA at SCK-CEN, SMILES at ARRONAX and TATTOOS at PSI.
[1] Michael Heines et al. Muonic x-ray spectroscopy on implanted targets. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 541:173–175, 2023. doi: https://doi.org/10.1016/j.nimb.2023.05.036.
[2] Claudia Lederer-Woods et al. Destruction of the cosmic γ-ray emitter Al 26 in massive stars: Study of the key Al 26 (n, p) reaction. Physical Review C, 104(2), 2021. doi: https://doi.org/10.1103/PhysRevC.104.L022803.
[3] Reinhard Heinke et al. Efficient production of high specific activity thulium-167 at Paul Scherrer Institute and CERN-MEDICIS. Frontiers in medicine, 8:712374, 2021. doi: https://doi.org/10.3389/fmed.2021.712374 .
[4] TRIDYN Application Examples - Helmholtz-Zentrum Dresden-Rossendorf, HZDR. https://www.hzdr.de/db/Cms?pNid=0&pOid=65033
[5] W. M¨oller and W. Eckstein. Tridyn—A TRIM simulation code including dynamic composition changes. Nuclear Instruments and Methods in Physics Research Section B, pages 814–818, 1984. doi: https://doi.org/0.1016/0168-583X(84)90321-5.
| Email address | marie.deseyn@kuleuven.be |
|---|---|
| Supervisor's Name | Thomas Elias Cocolios |
| Supervisor's email | thomas.cocolios@kuleuven.be |
| Funding Agency | FWO |
| Classification | Isotope production, target, and ion source techniques |
