# Real-Time Applicability of Emulated Virtual Circuits for Tokamak Plasma Shape Control

arXiv: https://arxiv.org/abs/2509.01789 · HTML: https://mlsanity.com/paper/2509.01789/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- Builds on 2 of its 17 references that are in the map.
- First posted on arXiv 1 Sep 2025.

## Builds on (most cited first, 2 of 2)

- [Towards practical reinforcement learning for tokamak magnetic control](https://mlsanity.com/paper/2307.11546/) (2023)
- [Neural net modeling of equilibria in NSTX-U](https://mlsanity.com/paper/2202.13915/) (2022)

## Built on by (most cited first, 1 of 1)

- [Real-time virtual circuits for plasma shape control via neural network emulators](https://mlsanity.com/paper/2605.14939/) (2026)

## Abstract (arXiv)

Machine learning has recently been adopted to emulate sensitivity matrices for real-time magnetic control of tokamak plasmas. However, these approaches would benefit from a quantification of possible inaccuracies. We report on two aspects of real-time applicability of emulators. First, we quantify the agreement of target displacement from VCs computed via Jacobians of the shape emulators with those from finite differences Jacobians on exact Grad-Shafranov solutions. Good agreement (≈5-10%) can be achieved on a selection of geometric targets using combinations of neural network emulators with ≈105 parameters. A sample of ≈105-106 synthetic equilibria is essential to train emulators that are not over-regularised or overfitting. Smaller models trained on the shape targets may be further fine-tuned to better fit the Jacobians. Second, we address the effect of vessel currents that are not directly measured in real-time and are typically subsumed into effective "shaping currents" when designing virtual circuits. We demonstrate that shaping currents can be inferred via simple linear regression on a trailing window of active coil current measurements with residuals of only a few Amp`eres, enabling a choice for the most appropriate shaping currents at any point in a shot. While these results are based on historic shot data and simulations tailored to MAST-U, they indicate that emulators with few-millisecond latency can be developed for robust real-time plasma shape control in existing and upcoming tokamaks.