Interpretative TRANSP analysis of JET baseline scenario: performance dependence on kinetic plasma parameters

The baseline scenario stands out as one of the most promising plasma states suitable for high- performance DT operation. This work focuses on the JET D-T baseline scenario (𝐼𝑝 = 3.0 𝑀 𝐴, 𝑞95 = 3, 𝛽𝑁 < 2) from the DTE2 campaign, held in 2021, and the more recent 2023 DTE3. One of the main operational differences between the two campaigns is the choice of beam fuels and net power use: the DTE3 campaign employs pure Deuterium beams with ~29 MW, whereas the DTE2 uses a 50-50 DT beam mix with ~24 MW. This distinction impacts not only the particle source but also the beam penetration and the plasma heating. To assess the scenario performance, an extensive interpretive modeling effort has been performed with TRANSP, comparing the numerical results against key indicators, such as neutron yield, stored energy, fast ion population and radiation profile. Starting from a DTE2 reference, simulations were performed changing the beam gas to pure D and scanning the injection energy. It results that a 20% reduction of the injection energy is needed to achieve a deposition similar to DTE2. On this DTE2 reference and its DTE3 counterpart, the dependence of various plasma parameters has been explored: Zeff was varied within the experimental error bars, and different impurity mixes were explored. In particular, for the DTE3 pulse the numerical neutron rate results larger than the experimental one, and only a fair agreement can be recovered by invoking a large dilution (higher Zeff and/or light impurity). The fast particle population was characterized in relation to the MHD activity, assuming an effective anomalous fast ion diffusivity. With this analysis, we try to assess the impact on the performance due to the differences between DTE2 and DTE3 in the setup of the experiments (e.g. NBI) and the experimental conditions (e.g. impurity mix composition).