Real-time Tomography-based Bayesian Inference from TCV Bolometry Data

TL;DR

This paper introduces a real-time, tomography-based Bayesian method for estimating radiated power in fusion plasmas using TCV bolometry data, enabling immediate plasma control adjustments.

Contribution

The authors develop a novel real-time Bayesian tomography technique that provides fast, accurate radiated power estimates without relying on synthetic training data.

Findings

Accurate real-time estimates of radiated power in various plasma regions.

Method is robust to detector faults and issues.

Open-source implementation of the technique is provided.

Abstract

Radiated power information is crucial to diagnose and optimize the performance of fusion plasmas. Traditionally, at the TCV tokamak, radiated power analysis has only ever been possible following plasma discharge termination. However, recently, TCV bolometer data have become available in real-time. This offers the opportunity of integrating the radiated power information into the TCV plasma control system. In this work, we propose a novel real-time tomography-based Bayesian technique allowing estimation of the power radiated from user-defined regions of interest in the plasma. The real-time estimates are obtained as computationally cheap linear combinations of bolometer measurements, using pre-computed coefficients that are optimized for the specific discharge planned. This method is not, thus, trained on a set of synthetic or tomographically reconstructed emissivity profiles. We detail the derivation of the technique and show its equivalence to traditional tomographic estimates under suitable conditions. We then demonstrate that this technique enables accurate real-time estimation of the total, core, divertor and main chamber radiated power, by its application to a representative and heterogeneous set of TCV discharges. Finally, we discuss the robustness of the technique to faulty detectors, showing that simple precautions allow safe handling of many common issues. The computational routines implementing the described technique are provided as open-source code.