Inverse Rendering of Fusion Plasmas: Inferring Plasma Composition from Imaging Systems

TL;DR

This paper introduces a differentiable rendering pipeline for tokamak plasma imaging that enables the estimation of plasma composition and physical quantities from images, including neutral Deuterium distribution, with high efficiency and flexibility.

Contribution

It develops a novel differentiable rendering framework that allows arbitrary plasma representations and enables joint estimation of multiple plasma parameters from imaging data.

Findings

Recovered neutral Deuterium distribution from imaging alone

Joint estimation of Deuterium, electron density, and temperature

Effective in realistic imaging conditions with sensor cropping and quantisation

Abstract

In this work, we develop a differentiable rendering pipeline for visualising plasma emission within tokamaks, and estimating the gradients of the emission and estimating other physical quantities. Unlike prior work, we are able to leverage arbitrary representations of plasma quantities and easily incorporate them into a non-linear optimisation framework. The efficiency of our method enables not only estimation of a physically plausible image of plasma, but also recovery of the neutral Deuterium distribution from imaging and midplane measurements alone. We demonstrate our method with three different levels of complexity showing first that a poloidal neutrals density distribution can be recovered from imaging alone, second that the distributions of neutral Deuterium, electron density and electron temperature can be recovered jointly, and finally, that this can be done in the presence of realistic imaging systems that incorporate sensor cropping and quantisation.