# Investigation of a Possible Material-Saving Approach of
## 4 Discussion  
The recovering shield was primarily designed just as a ground shield, able to reproduce the vacuum chamber's wall and give a possibility for a proper material dissipation evaluation. During the R&D work, it was also proposed that the material collected on the recovering shield may be dissolved chemically or electrochemically, depending on its type. A possible upgrade of the shield may include the introduction of a glass cylinder to help with the deposit pilling or dissolution. The removed coating can be used to study the growing behavior and evaluate the contamination present in the film; meanwhile, the produced CSTs are stored in the vacuum protection bags. Any destroying analysis can be applied for such deposits. Theoretically, in case of a proper adjustment of the construction, such deposits can be reused in the cylindrical shape as a magnetron target for the cylindrical magnetron [18]. Further experiments will involve the work with other metals and investigation of their recovering from the shield. Evaluating the two applied techniques, the MS deposition process has shown to be more energetic and efficient both from the material dissipation and deposition rate criteria. It could be explained by the nature of diode and magnetron discharge processes. The DC diode sputtering can be realized only in high gas pressure (more than 1 Pa), which creates a great number of collisions where the electrons lose their energy. In the case of the MS, the closed magnetic path near the target leads to the creation of a high flux of electrons, giving  
Figure 4: The cross-section thickness evaluation of MS deposition (**a**) and DS deposition (**b**). Figure 3: The cross-section SEM analysis of Cu deposit, produced with MS technique: columnar growth at the beginning of the layer (**a**) and changing from columnar to nucleus growth after the 100 \(\upmu\)m (**b**). as a result, a high-density plasma. Together with lower operating pressure, this gives the possibility to ions to be accelerated from plasma to the cathode without the loss of energy due to collision processes [19]. On the other hand, the main drawback of the MS, the target usage limitation, remains. Due to the specific erosion shape, only 27% of the target material mass may indeed be used from one target and even less will be deposited on the dedicated substrate. The remaining 73% of it could be used to produce a new target and it requires additional operating time. In the case of the DS deposition, this problem is completely avoided. The target material is uniformly eroded over the whole target surface, thus allowing for a longer target material usage. From this point of view, the DS appears to be quite a favorable technique. Moreover, the situation changes if we compare other parameters, such as the material losses, the amount of material deposited on the sample and the significant deposition rate drops. To deposit comparable thickness of the MS process (-900 um in our case), more than a 20-day-long deposition time would be required. In such a way, the production line and the related cost behind each CST manufacturing aimed at radioisotope production may thus be unaffordable. Moreover, the material losses in the DS process are higher compared to the MS. The protective shield collects more than 70% of the material sputtered in the vacuum chamber. Such a result clearly points out that the DS technique, without the usage of a recovering shield, may not be used for the expensive isotopically enriched material depositions, which, moreover, occur in almost all the cases. However, it may provide us a clear idea about benefits of both sputtering methods, prospects of designed shield utilization and its possible optimization. The deposition rate in the MS and DS processes is not influenced by the recovering shield utilization, which is confirmed by the deposition rate measurement in similar operating conditions. Currently, it is not feasible to carry out studies about the possible influence of temperature against the process deposition rate.