*3.1. Cyclotron Irradiation of <sup>89</sup>Y*

Zirconium-89 was produced by proton irradiation of commercially available <sup>89</sup>Y sputtered on a niobium coin using the <sup>89</sup>Y(p, n)89Zr reaction on a TR-24 cyclotron. Proton irradiation on <sup>89</sup>Y-targets has been investigated by several research groups [1,12,15,20,21]. Damage to the yttrium coins (yttrium solid and sputtered coins) was reported by Queern et al. [20]. In their production method, cyclotron irradiations were performed using proton beam energy 17.8 MeV degraded to 12.8 MeV using a 0.75 mm aluminium degrader. Beam currents of 40–45 µA were applied. Using the same irradiation conditions, we did not observe any damage to the yttrium target when irradiated for up to 4 h. The activity of the purified <sup>89</sup>Zr solutions was in the range of 866–1160 MBq after 2 h of irradiation using 45 µA beam current. Contamination of <sup>88</sup>Zr and <sup>88</sup>Y was not observed, as the formation of <sup>88</sup>Zr and <sup>88</sup>Y occurs via the <sup>89</sup>Y(p,2n)88Zr reaction at higher incident proton energies >13 MeV.
