April 4-6

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Author: Robert Hager
Requested Type: Consider for Invited
Submitted: 2022-03-07 08:50:23

Co-authors: S. Ku, A. Y. Sharma, C. S. Chang, M. Churchill, the XGC Team

Contact Info:
Princeton Plasma Physics Laboratory
100 Stellarator Road
Princeton, New Jersey   08540

Abstract Text:
A total-f electromagnetic gyrokinetic algorithm has been implemented in the particle-in-cell code XGC, which, for the first time, can simulate electromagnetic turbulence in tokamak boundary plasma in realistic divertor geometry together with neutral particle recycling and neoclassical physics. The generalization of XGC’s total-f method to the electromagnetic regime is based on the reduced delta-f mixed-variable/pullback algorithm [1,2] implemented in XGC and verified by M. Cole et al.[3] The new electromagnetic XGC now combines the traditional strengths of its total-f algorithm such as realistic tokamak geometry from the magnetic axis to the material wall, combined neoclassical and turbulence physics, neutral particle recycling, a nonlinear Fokker-Planck collision operator, and efficient, GPU-accelerated parallelization, with the numerical stability of the mixed-variable/pullback formulation that mitigates the “cancellation problem” and allows for relatively large time steps. We will present an overview of the electromagnetic total-f algorithm with all its major building blocks. A pair of simulations in a DIII-D-like H-mode boundary plasma comparing the electrostatic and electromagnetic total-f method will be discussed. These results show that electromagnetic simulation is necessary for a higher fidelity understanding of particle and heat transport even at the low values of beta at the pedestal foot around the separatrix. We will also present results from electromagnetic simulations of the divertor heat-load in a present-day tokamak and ITER (fusion power operation).

[1] R. Kleiber et al., Phys. Plasmas 23, 032501 (2016)
[2] A. Mishchenko et al., Phys. Plasmas 21, 052113 and 092110 (2014)
[3] Michael Cole et al., Phys. Plasmas 28, 034501 (2021)

Supported by the U.S. Department of Energy via the SciDAC program and by the INCITE program at leadership computing facilities.