Kinetic Equilibrium Prediction at TCV using RAPTOR and FBT

TL;DR

This paper introduces a new workflow combining RAPTOR and FBT codes for rapid kinetic equilibrium prediction at TCV, improving shot preparation accuracy and providing better estimates of plasma parameters for tokamak operation.

Contribution

The paper presents a novel coupling of RAPTOR and FBT codes for fast, accurate pre-shot plasma equilibrium prediction at TCV, enhancing operational planning and control.

Findings

Rapid pre-shot simulations are feasible across various plasma scenarios.

Coupling RAPTOR with FBT improves the accuracy of plasma shape and internal parameters.

The integrated approach provides more realistic estimates of coil currents and plasma parameters.

Abstract

We present results from a new Kinetic-Equilibrium Prediction (KEP) workflow and shot preparation for full TCV discharges, by coupling predict-first RAPTOR transport simulations with FBT inverse equilibrium calculations. RAPTOR is a 1.5D transport code which has been extensively used for plasma shot optimization and real-time modeling. We show that rapid pre-shot simulations can be performed directly using information from the pulse schedule across a wide range of plasma shapes and scenarios, given an estimate of the confinement quality factor H98(y,2) and line-averaged density. The resulting p' and TT' profiles are then provided to the pre-shot equilibrium computation performed by FBT - a static free-boundary solver routinely used at TCV - achieving convergence between the two codes in a few iterations. Finally, we show that this coupling, when integrated into the TCV shot preparation, improves the evaluation of the coil currents needed to match the target plasma shape; in particular providing an accurate estimate of critical quantities such as the internal inductance $l_i$ and normalized pressure $\beta_N$, giving more realistic information to tokamak operators about the expected pulse behavior and enabling them to adjust the plan correspondingly.