Gyrokinetic prediction of core tungsten peaking in a WEST plasma with nitrogen impurities

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Abstract
Tungsten peaking is predicted in the core of a WEST plasma with total-f gyrokinetic simulations, including both collisional and turbulent transport. This prediction is validated with a synthetic diagnostic of the bolometry. Although nitrogen impurities are shown to reduce the neoclassical peaking of tungsten on-axis, the overall tungsten peaking increases when nitrogen impurities are present, as they reduce the turbulence screening off-axis. This finding is important for the plasma current ramp-up phase of ITER, where light impurities seeding will be desirable to achieve low temperatures at the plasma-facing components and reduce tungsten sputtering. It provides further argument for applying early ECRH heating to maintain margins on the core power balance. The neoclassical peaking factor is cross-verified between XGC and FACIT. The heat flux at separatrix and the heat load width are modeled by XGC and compared to WEST data.
Funding Information
  • INCITE resources of the Oak Ridge Leadership Computing Facilities at the Argonne National Laboratory (DE-AC02-05CH11231)
  • INCITE resources of the Oak Ridge Leadership Computing Facilities at the Oak Ridge National Laboratory (DE-AC05-00OR22725)
  • SciDAC project ``Computational Evaluation and Design of Actuators for Core-Edge Integration’' (DE-FOA-0002924)
  • U.S. Department of Energy (DE-AC02-09CH11466)
  • resources of the National Energy Research Scientific Computing Center (ERCAP0028234)

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