## 2 SORGETINA RF Rotating Target
### Material
The evaluation of \(\Delta T_{m1}\) and \(\Delta T_{m2}\) are reported in Equation (2):  
\[\sigma_{\Delta T}=E\bigg{(}\alpha\Delta T_{m1}+\frac{2\alpha\Delta T_{m2}}{h}y \bigg{)} \tag{1}\]  
\[\Delta T_{m1}=\frac{\Delta T_{1}+\Delta T_{2}}{2} \tag{2a}\]  
\[\Delta T_{m2}=\frac{\Delta T_{2}-\Delta T_{1}}{2} \tag{2b}\]  
As shown in Figure 4, the stress due to the thermal effect for CuCrZr exceeds its yield strength being the normalised strength equal to 106%. Titanium is the material that provides the lowest value of the normalised strength with a value of 13%, also exhibiting a considerable resistance (high value of yield strength). Aluminium alloy provides a value of 71%, meaning that the strength capacity of material subject to the conditions considered is largely exploited but is still capable of withstanding increased stresses due to applied forces. A high value of yield strength is an important requirement that the structure has to fulfil, but is not the only parameter to consider in the choice of material. Although tungsten and titanium alloys provide the highest resistance and stiffness, their low thermal conductivity cannot be neglected, as it could compromise the correct operation of the system. Furthermore, standard materials such as the CuCrZr alloy show high material activation, and titanium alloy, which could be a candidate, has a high permeability to tritium. Using FISPACT-II code the dose trend of different materials after 1 year of exposure of 1 kg at 1 m distance from the ion source has been quantified [14]. More in detail, the number of D + T particles onto the target considering 200 days/year is about 9 \(\times\) 10\({}^{25}\) particles in one activity year. Because of the low D and T energy (300 keV), these are completely stopped by the titanium layer of the target. The main effect on the Ti layer is physical sputtering. It is, indeed, foreseen that a Ti deposition plant, as described in [3], can be used to recover the sputtered Ti layer. Finally, the charged particle beam is not a concern for dpa. As far as neutron-induced dpa is concerned, the neutron emission rate is in the range of 5-7 \(\times\) 10\({}^{13}\) s\({}^{-1}\). This emission rate may induce a fraction of dpa in aluminium. Thus, over 200 days/year, the dpa on the target is not detrimental. As a matter of fact, over a typical lifetime of the target (2-3 years) no primary beam neutron-induced thermal property changes are likely to occur. The aluminum alloy showed the lowest material activation as reported in Figure 5.  
Figure 2:0 Dose trend of different materials after 1 year of exposure of 1 kg at 1 m distance from the ion source (FISPACT-II code results) [14]. On the other hand, the aluminium alloy exhibited good mechanical resistance, thermal conductivity, and chemical compatibility with water [4]. Aluminium alloy has many further advantages, such as lower cost, light density, good heat dissipation, recyclability, and low neutron activation. For these reasons, aluminium alloy represents the best compromise to fulfil the above criteria and therefore is the most promising candidate as the material for the rotating target. In fact, thanks to its mechanical properties, it represents the best compromise between the required performance criteria: thermal exchange, mechanical strength, and low neutron activation.