Physics-Informed Deep Learning Model for Line-integral Diagnostics Across Fusion Devices

TL;DR

This paper presents Onion, a physics-informed deep learning model for reconstructing 2D plasma profiles from line-integral data, improving accuracy and adaptability across fusion devices by integrating physical principles and specialized loss functions.

Contribution

Introduction of Onion, a physics-informed neural network architecture that enhances plasma profile reconstruction accuracy and can be adapted to various backbone networks in fusion diagnostics.

Findings

Reduced average relative error by approximately 0.84x10^(-2) on synthetic data

Achieved about 0.06x10^(-2) error reduction on experimental data

Improved model performance with Softplus activation in final layers

Abstract

Rapid reconstruction of 2D plasma profiles from line-integral measurements is important in nuclear fusion. This paper introduces a physics-informed model architecture called Onion, that can enhance the performance of models and be adapted to various backbone networks. The model under Onion incorporates physical information by a multiplication process and applies the physics-informed loss function according to the principle of line integration. Prediction results demonstrate that the additional input of physical information improves the deep learning model's ability, leading to a reduction in the average relative error E_1 between the reconstruction profiles and the target profiles by approximately 0.84x10^(-2) on synthetic datasets and about 0.06x10^(-2) on experimental datasets. Furthermore, the implementation of the Softplus activation function in the final two fully connected layers improves model performance. This enhancement results in a reduction in the E_1 by approximately 1.06x10^(-2) on synthetic datasets and about 0.11x10^(-2) on experimental datasets. The incorporation of the physics-informed loss function has been shown to correct the model's predictions, bringing the back-projections closer to the actual inputs and reducing the errors associated with inversion algorithms. Besides, we have developed a synthetic data model to generate customized line-integral diagnostic datasets and have also collected soft x-ray diagnostic datasets from EAST and HL-2A. This study achieves reductions in reconstruction errors, and accelerates the development of surrogate models in fusion research.