Investigation of impurity transport in SPARC H-mode scenarios.

This work presents an overview of predicted SPARC H-mode performance, examining the sensitivity of fusion gain and H-mode robustness (defined as Psep/PLH, where PLH is computed with Martin scaling) to selected input assumptions. Extensive performance databases have been generated for three H-mode scenarios using the ASTRA framework. Turbulent transport is modeled with the quasilinear TGLF-SAT2 EM model, while pedestal stability is predicted using a neural network (NN) trained on EPED results. Within this framework, several uncertain input parameters are systematically varied to evaluate their impact on performance. The results indicate that low density and high input power are optimal for achieving high performance while preserving a robust H-mode, although the compatibility of these scenarios with power exhaust has not been investigated. Additional simulations, combining the FACIT neoclassical model, TGLF and STRAHL (for charge state equilibrium), have been conducted to more reliably assess the effect of high impurity content on the core radiation. The simulations include parameter scans of impurity sources, ion cyclotron heating power, pedestal-top density, D/T mix percentage, and plasma rotation due to intrinsique torque, to identify favorable operational windows. The new findings reduce the uncertainties on performance and H-mode access robustness, showing qualitative agreement with earlier databases.

This work was supported by Commonwealth Fusion Systems under RPP020.