## 2 Methods and Materials
Every experiment in the C40 and C41 campaigns serves multiple purposes, focusing on issues such as plasma confinement modes, radiometric and neutronic measurements, and the testing of operational and auxiliary systems and procedures. Figure 1: The 14 MeV neutron (D-T reaction) budget for irradiation campaigns. The entire scenario consists of 425 days, of which 151 days are dedicated to irradiation. As for the second stage of the tritium experiment, some other experiment sessions referred to as M18 and M21 are also included in this campaign in our calculation due to their being mixed into the C40 campaign and presenting significant budgets for DD and DT neutrons. In general, the DTE2 (C41) daily neutron total budgets are much higher on average (almost by two orders of magnitude) compared to those of the C40 campaigns. However, the difference is smaller if you consider the cumulative neutron budgets. The subject of investigation were eight metallic foils of different elemental compositions located at the JET outer long-term irradiation station (OLTIS):  
- Silver;  
- Gold;  
- Manganese (88%) and nickel (12%);  
- Niobium;  
- Nickel;  
- Rhodium;  
- Titanium;  
- Yttrium. The compositions of the foils are selected in accordance with their potential use as part of activation detectors [20]. The specific activities and dose rates for the metallic foils were calculated in accordance with the JET C40 and DTE2 campaigns. Foils located at the JET OLTIS are affected by neutrons created from deuterium-deuterium, deuterium-tritium, and tritium-tritium fusion reactions. The neutron flux densities were calculated with the Monte Carlo N-Particle transport code (MCNP6.2) [21] with an already validated JET MCNP model [22] (the MCNP geometry is presented in Figure 3) together with the FENDL-3.1d [23] nuclear data library. Neutron spectra (Figures 4 and 5) were adapted for the C40 and DTE2 campaigns. In total, 151 unique spectra were created for each irradiation day by varying the DD, TT, and DT neutron budgets. Figure 2: The 2.45 MeV neutron (D-D reaction) budget for irradiation campaigns. Figure 4: Neutron spectra for DD, DT, and TT reactions for the OLTIS sample irradiation location during the C40 campaign (day 54). Figure 5: Neutron spectra for DD, DT, and TT reactions for the OLTIS sample irradiation location during the DTE2 campaign (day 257). Figure 3: MCNP geometry model of the JET and the location of the OLTIS. The irradiation scenario considered for the activation calculations was based on the current JET operation schedule. For simplification, the assumption was made that the device operated continuously on the day of operation. The operation schedule is provided on a day-to-day basis. In reality, the irradiation pulses are very short and often scattered across the day for a specific experimentation task at the JET. C40 Campaign, part 1:  
The C40 campaign (also known as a tritium experiment) is expected to have 2.92 \(\times\) 10\({}^{18}\), 5.84 \(\times\) 10\({}^{19}\), and 1.28 \(\times\) 10\({}^{19}\) neutron yields for DD, TT, and DT fusion reactions, respectively. Although it is a pure tritium experiment, due to the possible residual presence of deuterium in the vacuum vessel (with a conservative estimate of 1%), the majority of fusion reactions will still be DT reactions. Before the start of the tritium campaigns, efforts to minimize the presence of deuterium are expected. DTE2 Campaign:  
The DTE2 campaign (also known as a deuterium-tritium experiment) is expected to have 6.10 \(\times\) 10\({}^{18}\), 1.22 \(\times\) 10\({}^{19}\), and 9.29 \(\times\) 10\({}^{20}\) neutron yields for DD, TT, and DT fusion reactions, respectively. DTE2 should provide the highest fusion neutron yield so far of all magnetic confinement fusion devices in experimental settings. C40 Campaign, part 2:  
The second part of the C40 campaign is expected to have 5.08 \(\times\) 10\({}^{18}\), 1.16 \(\times\) 10\({}^{19}\), and 2.26 \(\times\) 10\({}^{19}\) neutron yields for DD, TT, and DT fusion reactions, respectively.