Isotope Harvesting at FRIB: Upcoming Opportunities for Scientific Applications

Prof. Katharina Domnanich
Michigan State University

When exotic, secondary beams are produced at the Facility for Rare Isotope Beams (FRIB), a majority of the accelerated primary beam remains unused and will be stopped in a water-traversed, spinning drum of Ti64 alloy. The dissipation of such large energy amounts induces the formation of a plethora of valuable radionuclides. Exploratory research with the heavy ion beams from the National Superconducting Cyclotron Laboratory (NSCL) demonstrated the feasibility of a synergistic collection of radionuclides from the aqueous and gaseous phase, and the process became colloquially known as ‘isotope harvesting’. [1]

In this talk, I will give an overview of the isotope harvesting process, first with a focus on the collection of ⁶²Zn from a stopped ⁷⁸Kr beam at the NSCL. The positron-emitting ⁶²Zn (t_1/2= 9.2 h) decays to the short-lived ⁶²Cu (t_1/2= 9.7 min) and currently both find collective application in nuclear medicine for the ⁶²Zn/⁶²Cu PET generator. The developed purification method facilitated the separation of ⁶²Zn from accompanying radioactive and stable nuclides. Furthermore, the role of zinc as an essential nutrient in many biological systems has led to the utilization of the obtained ⁶²Zn in a proof-of-principle plant uptake and imaging experiment. [2]

In the normal operation mode of FRIB, a broad variety of multiple isotopes of each element will be created, and often direct harvesting efforts can only yield samples of moderate radioisotopic purity. An option to increase the spectrum of available pure radioisotopes would be through the implementation of mass separation. At FRIB, a suitable mass analyzer is already part of the existing infrastructure, and could be utilized to establish a prototype mass separator. [3] The so-obtained, radioisotopically pure samples will be available for the preparation of targets for neutron reaction measurements and other scientific studies. In addition, the development of a target manufacturing program will also benefit the stand-alone operation of the on-site Re-Accelerator facility and thereby facilitate the parallel operation of multiple facilities at FRIB. In the second part of this talk, I will give an overview of the current target preparation efforts in support of the Re-Accelerator program. [4] Furthermore, an outlook towards the prospective extension of the existing isotope harvesting program and the future research on radioactive targetry development will be given.

References

[1]      E. P. Abel et al., Isotope Harvesting at FRIB: Additional Opportunities for Scientific Discovery, 2018.

[2]      K. A. Domnanich, C. K. Vyas, E. P. Abel, C. Kalman, W. Walker, and G. W. Severin, Harvesting ⁶²Zn from an Aqueous Cocktail at the NSCL, New J. Chem. 44, 20861 (2020).

[3]      A. Villari et al., Commissioning and First Accelerated Beams in the ReAccelerator (ReA3) of the National Superconducting Cyclotron Laboratory, MSU, in IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference (2016), pp. 1287–1290.

[4]      S. Rogers, Y. Liu, S. Schwarz, and C. Sumithrarachchi, Batch Mode Ion Source Operation in the N4 Vault, in The Greensheet (2022), p. 4.

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