Cross-section measurement of 165Ho(d,x) reactions and comparison of deuteron and proton activation of holmium for165Er production

Erbium-165 is a pure Auger electron emitter with high potential for targeted radionuclide therapy of micrometastases. Following our previous study of the proton-induced pathway, this work investigates the production route via 165 Ho deuteron activation. Excitation functions for the 165 Ho (d,x) 165 Er, 164m,g Ho, and 166g Ho reactions were measured using the stacked-foil activation technique in the 6–20 MeV energy range at the U-120M cyclotron. We report the first-ever experimental cross sections for the production of 164m,g Ho via the deuteron route. The measured data show good agreement with earlier experiments, but reveal some discrepancies with the TENDL-2025 library. Thick target yield calculations based on the experimental data confirm that deuteron activation is superior for large-scale production, offering a fourfold higher yield compared to the proton-induced route (1 092 GBq vs. 236 GBq for a 10 h irradiation at 50 μA). Co-produced 166 Ho may be chemically separated from the product. These findings demonstrate that 165 Ho (d,2n) 165 Er reaction is optimal for routine production of 165 Er.