Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator

Abstract

Experiments were performed during the operational phase (OP) 1.2a of W7-X to verify predictions of potential overload conditions corresponding to certain high-power long-pulse OP2 scenarios. Heat flux measurements were obtained in a series of magnetic configurations designed to mimic the magnetic topology evolution caused by net toroidal current and beta, which is not directly accessible in OP1.2. The measured heat fluxes are compared to field line diffusion calculations used to design the scraper element, which provides one potential solution to the overload issue by intercepting heat flux that would otherwise be incident on low-rated divertor edges. The experimental flux patterns are qualitatively reproduced by the simulations in position and magnitude for ad-hoc cross-field diffusivities near the value used to design the scraper element. However, some important differences including an anomalous shift towards the pumping gap and low-rated components is observed.

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

“…The simulation data is compared with experimental data from W7-X from the infra-red (IR) heat flux diagnostic and the reciprocating electric probes. This work extends previous work and especially addresses remaining discrepancies between simulations and experiments [14][15][16][17][18][19][20][21]. The here presented analysis is restricted to the magnetic standard configuration.…”

Overview of the results from divertor experiments with attached and detached plasmas at Wendelstein 7-X and their implications for steady-state operation

“…• An additional divertor component, the scraper element, was designed to protect the edges of the primary divertor and the pumping gap throughout this evolution during specific high-power long-pulse operational scenarios [48,49]. It showed promising results in the discharges created to mimic the strike line geometry expected in a plasma scenario, in which the toroidal current is evolving on the L/R time (O ∼ few 10 s) scales from 0 kA to 43 kA.…”

Effects of toroidal plasma current on divertor power depositions on Wendelstein 7-X

“…The dependence of the bootstrap current on the magnetic configuration has been identified in a magnetic configuration scan discussed in [7]. The evolution of the toroidal current and the effect on the heat flux profile for the mimic configurations are shown in [8].…”