The FreeGSNKE Pulse Design Tool (FPDT): a computational framework for evolutive plasma scenario and control design
In this paper we present the FreeGSNKE Pulse Design Tool (FPDT), an open-source, purely Python-based computational framework that enables in silico predictive design and testing of experimental tokamak plasma scenarios and control strategies. The FPDT couples FreeGSNKE’s evolutive equilibrium solver with a new virtual Plasma Control System (PCS), containing modular and customisable controllers. Given a set of user-defined waveforms and control parameters, the virtual PCS uses a combination of feedback and feedforward control to modulate plasma current, position, and shape, while adhering to machine safety limits on poloidal field coil currents and voltages. The resulting framework allows simulation of the controlled dynamic evolution of plasma equilibria, along with the associated currents in both active poloidal field coils and passive conducting structures. The FPDT can be used to develop plasma scenarios, test control schemes, calibrate control parameters, and assess how measurement uncertainty affects plasma evolution and subsequent control, thereby reducing iterative and expensive experimental testing on a physical tokamak. The FPDT is machine-agnostic and can be customised to implement different control algorithms tailored to the specific tokamak of interest. Here, we outline the overall framework and validate its performance on plasma discharges on the MAST Upgrade tokamak, demonstrating excellent quantitative agreement between the FPDT simulations, the desired control waveforms, and the experimental shot data. It is our aim that this extension to the FreeGSNKE open-source suite of codes will encourage more reproducible and collaborative research in plasma modelling and control.