Automated ICRF heating surrogate modeling via machine learning

¹ Princeton Plasma Physics Laboratory, Princeton, NJ 08540, USA
² Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
³ San Francisco State University, San Francisco, CA 94132, USA
⁴ CEA-IRFM, F-13108 Saint-Paul-lez-Durance, France
⁵ University of California, Los Angeles, CA 90095, USA
⁶ MIT Plasma Science and Fusion Center, Cambridge, MA 02139, USA

^* Corresponding author: asvillar@pppl.gov

Published online: 7 January 2026

Abstract

This work introduces automated machine learning workflows that address critical bottlenecks in surrogate model development for Ion Cyclotron Range of Frequencies (ICRF) heating applications. The automated framework includes data analysis tools that transform raw datasets into actionable insights in seconds, replacing weeks of manual exploratory effort and ensuring consistent, reproducible dataset characterization. By integrating advanced hyperparameter optimization (HPO) methods including Bayesian optimization via BoTorch and Tree-structured Parzen Estimators (TPE), the framework significantly reduces model development time from weeks to hours, decreasing computational cost and required expertise, while enabling high-accuracy surrogate models. Compared to traditional hyperparameter scanning (HPS) techniques such as methodical, randomized, and grid searches, HPO methods achieve superior convergence and predictive performance, even when compared to already well-tuned reference models. On NSTX High Harmonic Fast Wave (HHFW) heating datasets, both Random Forest Regressor (RFR) and neural network surrogates demonstrate improved accuracy, achieving R² values beyond 0.97 and 0.98, respectively. The results show that while HPO gains are modest for robust architectures like RFR, they become essential for more sensitive models such as neural networks, highlighting the trade-offs across optimization strategies. Through automated workflows that eliminate manual hyperparameter tuning and require minimal ML expertise, this work enables widespread adoption of high-fidelity surrogate models across the fusion community for real-time plasma control, uncertainty quantification, rapid experimental scenario development, and integrated system optimization.