## 3 Results and Discussion  
We began by examining the distillation profile for different distillation temperatures. This was done using targets produced from natural tellurium dioxide. The targets were bombarded with approx. 1.5 \(\upmu\)Ah of 14.8 MeV protons and subsequently distilled, using temperatures of 600 \({}^{\circ}\)C, 675 \({}^{\circ}\)C, 700 \({}^{\circ}\)C and 750 \({}^{\circ}\)C. The collection tube was changed every 10 min, the first one changed 10 min after the oven had reached the set temperature. The distillation tubes were subsequently measured and the produced isotopes quantified by gamma spectroscopy. Because gamma spectroscopy was performed several days after EOB, the measurements of \({}^{123}\)I were associated with very large uncertainties due to low residual activity. The data obtained of \({}^{123}\)I activities were therefore omitted. As described by others [5], we found that distillation speed increases rapidly when the glass melts. It should be noted that the melting point of the 95% TeO\({}_{2}\)/5% Al\({}_{2}\)O\({}_{3}\) mix, is significantly lower than that of pure TeO\({}_{2}\) (733 \({}^{\circ}\)C), and has a measured value around 685-690 \({}^{\circ}\)C. Above this temperature, \(\sim\)95% of the \({}^{124}\)I activity is distilled out of the target material in 40 min and more than 98% of the \({}^{124}\)I activity is distilled in 60 min (Figure 3). Figure 3: Graph showing the percent \({}^{124}\)I distilled as a function of time. The first collection tube was mounted at room temperature and changed 10 min after the set temperature was reached. Figure 2: Computer-aided design (CAD) drawing of the quartz distillation tube designed to hold a target of 24 mm in diameter. The actual length of the distillation tube can be changed to fit the length of the tube furnace. **1**: Side view **2**: Top view **3**: End view. (Unit: mm). Loss of target material is not only expensive, but can also lead to inconsistent production yields due to thinning of the target. To estimate the loss of target material associated with distillation temperatures, two targets made from natural tellurium dioxide with 5% aluminum oxide were prepared. The target backings were of slightly different designs; One with a groove, diameter of 10 mm and depth 1.8 mm, and one of diameter 11 mm with depth of 1 mm and both targets approximately 280 mg/cm\({}^{2}\) thick. The targets were heated in intervals of 1 hour, at temperatures ranging from 650 to 810 \({}^{\circ}\)C and weighed between each heating stage. It was found that as long as the temperature is below melting point there is no significant loss of target material. However, as the temperature rises above 750 \({}^{\circ}\)C, the losses start rising exponentially (Figure 4). When we got these results they were initially difficult to compare to results in literature, where losses are often given as a percentage of total target weight. As evaporation is a function of surface area and not mass, we believe a better unit is loss/time/area. Loss given as percentage of total mass, is acceptable as long as the targets discussed are of similar thickness. A slanted target however will have a very high surface to volume ratio, compared to a normal target of the same effective thickness, and will therefore lose a larger percent of target mass during distillation. Using loss/time/area will make it easier to estimate and compare losses of different target designs. During the distillation tests following proton bombardment of natural tellurium targets, we stumbled on an initially surprising result. We found that \({}^{124}\)I, \({}^{126}\)I and \({}^{130}\)I were not distilled out of the target at the same rate when distilled at lower temperatures (Figure 5). Figure 4: Graph showing the loss of target material associated with 1 h of distillation at a range of temperatures. It should be noted that these experiments were done without any air flow over the target disc.