{"ID":2876090,"CreatedAt":"2026-06-01T04:54:23.091178241Z","UpdatedAt":"2026-06-01T04:54:23.091178241Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2509.01789","arxiv_id":"2509.01789","title":"Real-Time Applicability of Emulated Virtual Circuits for Tokamak Plasma Shape Control","abstract":"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 ($\\approx$5-10%) can be achieved on a selection of geometric targets using combinations of neural network emulators with $\\approx10^5$ parameters. A sample of $\\approx10^{5}-10^{6}$ 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 Ampères, 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.","short_abstract":"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 targ...","url_abs":"https://arxiv.org/abs/2509.01789","url_pdf":"https://arxiv.org/pdf/2509.01789v1","authors":"[\"Pedro Cavestany\",\"Alasdair Ross\",\"Adriano Agnello\",\"Aran Garrod\",\"Nicola C. Amorisco\",\"George K. Holt\",\"Kamran Pentland\",\"James Buchanan\"]","published":"2025-09-01T21:37:48Z","proceeding":"physics.plasm-ph","tasks":"[\"physics.plasm-ph\",\"cs.LG\",\"eess.SY\",\"physics.data-an\"]","methods":"[]","has_code":false}