First heat flux estimation in the lower divertor of WEST with embedded thermal measurements

TL;DR

This paper presents a method for estimating heat flux in the WEST tokamak's lower divertor using embedded thermocouples and FBG sensors, combined with a 2D heat transfer model and inverse techniques, validated across different magnetic configurations.

Contribution

It introduces a novel approach integrating embedded thermal measurements with advanced modeling to estimate plasma heat flux in the divertor region.

Findings

Heat flux estimates are consistent with magnetic reconstructions.

The method captures spatial and temporal evolution of heat flux.

Validation across different magnetic configurations demonstrates robustness.

Abstract

The present paper deals with the surface heat flux estimation with thermocouples (TC) and fiber Bragg grating (FBG) embedded in the plasma facing components (PFC) of the WEST tokamak. A 2D heat transfer model combined with the conjugate gradient method (CGM) and the adjoint state is used to estimate the plasma heat flux deposited on the PFC. The plasma heat flux is characterized by the time evolution of its amplitude and spatial shape on the target (heat flux decay length $\lambda^t_q$, power spreading in the private flux region $S^t$ and the strike point location $x_0$). As a first step, five ohmic pulses have been investigated with different magnetic configuration and divertor X-point height varying from 44 to 68 mm from the surface. Despite an outboard shift, the relative displacements of the outer strike point as well as the heat flux decay length derived from the TC/FBG systems are consistent with the magnetic equilibrium reconstruction.