## 4 Discussion  
According to data reported by [PERSON] et al., the optimal cross-section is at 750.8 \(\pm\) 1.5 mb while using 12.46 MeV \(E_{p}\)[7]. Increasing \(E_{p}\) beyond this level will increase the \({}^{89}\)Zr production yield, but long half-life by-products, such \({}^{88}\)Zr and \({}^{88}\)Y, will then be produced. Thus, \({}^{89}\)Zr production is not optimal using medium energy cyclotron, except considering the reduction of the \(E_{p}\), which can be achieved with an energy degrader. We designed different size target degraders and holders in different materials (Figure 1) to be used with incident \(E_{p}\) of 16.2-18 MeV. An aluminum holder/degrader was first selected for its high-energy transfer [13], which renders more efficient target cooling during the irradiation. Niobium has high chemical resistance and was selected due to its high melting temperature and to avoid any deterioration of the target body during cleaning with hydrochloric acid to remove any trace of unknown metals [14]. The degradation of the beam energy with our designed degraders was achieved without damage, except for the Nb degrader while using long irradiation times (Figure 1B). Under these conditions, the \({}^{89}\)Y-pressed powder oxidized into Y\({}_{2}\)O\({}_{3}\), which is poorly soluble and required a high volume of 12N HCl for its dissolution and purification [24]. Furthermore, the aluminum degrader presents better heat transfer and no local overheating was observed for the Al-21-1 degrader (Figure 1A) when 15 and 40 \(\upmu\)A were applied to \({}^{89}\)Y-foil at 13.3 and 15 MeV for 4.5 and 1.5 h, respectively. The production yield depends on the incident \(E_{p}\), the degrader material, and the beam size, as well as the density and thickness of the target materials. The highest yields were found for 0.50-mm thick \({}^{89}\)Y-foil target (two foils). Increasing the number of foils beyond this thickness did not improve the yield for an \(E_{p}\) of 11.3 MeV. The production yield was also affected by the target diameter. Indeed, higher yields were obtained with the 13-mm diameter targets that provided a better fit with the beam size of \(\sim\)10 mm. One should note that a current as high as 40 \(\upmu\)A could be applied when the Al-13  
Figure 5: Representative \(\gamma\)-spectra of \({}^{89}\)Zr performed after (**A**) \({}^{89}\)Zr purification using \({}^{89}\)Y-foil and irradiation performed at 11.3 MeV, (**B**) six months, using \({}^{89}\)Y-foil and irradiation performed at 13.3 MeV, and (**D**) six months, using \({}^{89}\)Y-pressed powder and irradiation performed at 11.3 MeV. Samples were measured using a H\(\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{\rm{ \rm{\rm{\rm{\rm{ \rm{ \rm{  \rm{ }}}}} {{}}}{{  
holder was used as compared to all other degraders, the cooling system being more efficient. Indeed, the Al back support is thinner for the Al-13 holder (0.5 mm) as compared to that of other degraders (1.0 mm) (Figure 1). In addition, high production yield values were obtained while using both foil and pressed targets. The highest yield (54 \(\pm\) 2.9 MBq/\(\upmu\)A-h) obtained at 15.0 MeV is similar to that the one reported by [PERSON] et al. (56.24 \(\pm\) 4.1 MBbq/\(\upmu\)A-h) [5] for a similar foil target thickness. As shown in Table 2, the production yield reported for \({}^{89}\)Y-pressed target (49.5 \(\pm\) 1.2 MBq/\(\upmu\)A-h) is slightly lower than the one that was reported by [PERSON] et al. (66.6 MBq/\(\upmu\)A-h) while using \({}^{89}\)Y-oxide pressed targets irradiated at 16.2 MeV from deuteron [8]. [PERSON] et al. reported that the increase of beam current and irradiation time was more challenging using pressed targets [8]. In the present study, we were able to irradiate at 15 and 40 \(\upmu\)A for 4.2 and 1.5 h, respectively, without overheating the \({}^{89}\)Y-target material. The automated cassette-based module that was used in this work is simple, reliable, and provides reproducible results with high-recovered activity.