Abstract
Simulations of heat fluxes to the plasma facing components in the Wendelstein 7-X stellarator will be tested in its next operational phase. The simulations consist of core transport calculations that determine the evolution of the kinetic profiles and the toroidal current, which modifies the fluxes to the divertor, as the magnetic geometry changes. An additional divertor component, the scraper element, was designed to protect the edges of the primary divertor throughout this evolution during certain high-power long-pulse operational scenarios. The effect of unknown parameters of the heat flux calculations, namely, the cross-field thermal diffusivity and the magnetic field structure, is explored. The predicted scaling of the heat flux widths and magnitudes is presented, along with a new method of calculating the 3-D magnetic field structure required to perform the flux calculations.
Highlights
A validated simulation capability to calculate heat and particle fluxes to plasma facing components (PFCs) is a critical need for current and future magnetic confinement fusion devices
Calculation of the fluxes to the PFCs for stellarator operating scenarios often consist of 1.5D core transport simulations (1D radial transport + 2D magnetic surface geometry) to account for the evolution of the kinetic profiles and toroidal current, coupled to a 3D model for the edge transport and PFC geometry
We present a discussion of these simulations, experiments to assess the effect of scraper elements in the operational phases of Wendelstein 7-X (W7-X), and methods for validating the underlying simulations, with a focus on energy transport
Summary
A validated simulation capability to calculate heat and particle fluxes to plasma facing components (PFCs) is a critical need for current and future magnetic confinement fusion devices. For certain desirable operational scenarios for the Wendelstein 7-X (W7-X) stellarator, these simulations result This manuscript has been authored by UT-Battelle, LLC under Contract No DE-AC05-00OR22725 with the U.S Department of Energy. As the manufacture and installation of these new components adds significant cost, the simulations leading to the prediction of the overload, and the effects of the scraper elements on operation must be validated. Deviation from the current-optimized configurations leads to predictions of bootstrap currents on the order of 40 kA, depending on the configuration and plasma scenario [3,4] This is problematic as a net toroidal current modifies the edge rotational transform, which must be kept fixed to have the island chain static relative to the divertor plates.
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