Real-time identification of the current density profile in the JET Tokamak: method and validation

TL;DR

This paper introduces a real-time method for reconstructing the plasma current density profile in the JET Tokamak using a combination of measurements and a C++ software implementation, validated through experimental comparisons.

Contribution

A novel real-time reconstruction method for plasma current density in a Tokamak, integrating multiple measurements with a C++ software implementation for improved performance.

Findings

Successful real-time reconstruction validated on JET

Comparison with off-line codes shows high accuracy

Method enables better control of plasma equilibrium

Abstract

The real-time reconstruction of the plasma magnetic equilibrium in a Tokamak is a key point to access high performance regimes. Indeed, the shape of the plasma current density profile is a direct output of the reconstruction and has a leading effect for reaching a steady-state high performance regime of operation. In this paper we present the methodology followed to identify numerically the plasma current density in a Tokamak and its equilibrium. In order to meet the real-time requirements a C++ software has been developed using the combination of a finite element method, a nonlinear fixed point algorithm associated to a least square optimization procedure. The experimental measurements that enable the identification are the magnetics on the vacuum vessel, the interferometric and polarimetric measurements on several chords and the motional Stark effect. Details are given about the validation of the reconstruction on the JET tokamak, either by comparison with 'off-line' equilibrium codes or real time software computing global quantities.