Magnetic potential based formulation for linear and non-linear 3D RF sheath simulation. (1st February 2023)

• Record Type: Journal Article
• Authors: Shiraiwa, S.; Bertelli, N.; Tierens, W.; Bilato, R.; Hillairet, J.; Myra, J.; Kohno, H.; Poulos, M.; Ono, M.
• Is Part Of: Nuclear fusion. Volume 63:Number 2(2023)
• Publication Date: 2023-02-01
• Subjects: ICRF -- full-wave simulation -- RF sheath; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aca6f9
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: This paper reports a new numerical scheme to simulate the radio-frequency (RF) induced RF sheath, which is suitable for a large 3D simulation. In the RF sheath boundary model, the tangential component of the electric field ( E t ) is given by the gradient of a scalar electric field potential. We introduce two additional scalar potentials for the tangential components of the magnetic field, which effectively impose the normal electric displacement ( D n ) on the plasma sheath boundary condition via in-homogeneous Neumann boundary condition and constrain the tangential electric field on the surface as curl-free ( ∇ × E t = 0 ). In our approach, the non-linear sheath impedance is formulated as a natural extension of the large thickness (or asymptotic) sheath limit ( D n = 0 ), allowing for handling both asymptotic and non-linear regimes seamlessly. The new scheme is implemented using the Petra-M finite element method analysis framework and is verified with simulations in the literature. The significance of non-linearity is discussed in various plasma conditions. An application of this scheme to asymptotic RF sheath simulation on the WEST ICRF antenna side limiters is also discussed.