Parametrisation of target heat flux distribution and study of transport parameters for boundary modelling in W7-X

TL;DR

This study models the scrape-off layer of the stellarator W7-X using EMC3-EIRENE, validating transport parameters against experimental data and highlighting discrepancies in transport coefficients and temperature predictions.

Contribution

It introduces a parametrization of the target heat flux distribution and investigates transport parameters for boundary modeling in W7-X.

Findings

Transport coefficients around 0.2 m^2/s match strike line width observations.

Discrepancies exist between modeled and upstream measured temperatures.

Validation of the transport model against experimental data is achieved.

Abstract

Modelling the scrape-off layer of a stellarator is challenging due to the complex magnetic 3D geometry. The here presented study analyses simulations of the scrape-off layer (SOL) of the stellarator Wendelstein 7-X (W7-X) using the EMC3-EIRENE code for the magnetic standard configuration. Comparing with experimental observations, the transport model is validated. Based on the experimentally observed strike line width, the anomalous transport coefficients, used as input to the code are determined to around $0.2\,$m$^2/$s. This is however in disagreement with upstream measurements, where such small cross-field transport leads to temperatures higher than measured experimentally.