Reduced dynamic modeling of the Infinity Two stellarator plasma for studying access to ignition

In this work we present a 0-D dynamic model for investigating steady-state accessibility of high-gain and ignited operating points in Infinity Two, a high-field quasi-isodynamic stellarator utilizing non-planar, high-temperature superconducting magnets [1]. Previous T3D-GX-SFINCS simulations have demonstrated the viability of high-gain and ignited steady-state operating points enabled by magnetic field optimization and density profile shaping [2].

The dynamic model consists of coupled energy and particle balance equations and includes idealized pellet fueling and ECRH power sources, radiation, DT fusion, edge impurity seeding, and confinement losses. Confinement losses are modeled considering both empirical scalings and confinement times derived from coupled T3D-GX simulations.

Initial simulations demonstrate PID feedback control of fusion power through coordinated ECRH power and pellet injection rate modulation. This framework provides the foundation for closed-loop control design targeting specific operating points. Future work enabling realistic 1-D dynamic profile evolution with physics-based actuator and diagnostic models will be discussed.