Abstract
For applications of ICRF power in fusion devices, control of RF sheath interactions is of great importance. A sheath boundary condition (SBC) was previously developed to provide an effective surface impedance for the interaction of the RF sheath with the waves. The SBC enables the surface power flux and rectified potential energy available for sputtering to be calculated. For legacy codes which cannot easily implement the SBC, or to speed convergence in codes which do implement it, we consider here an approximate method to simulate SBCs by post-processing results obtained using other, e.g. conducting wall, boundary conditions. The basic approximation is that the modifications resulting from the generalized SBC are driven by a fixed incoming wave which could be either a fast wave or a slow wave. The method is illustrated in slab geometry and compared with exact numerical solutions; it is shown to work very well.
Highlights
For applications of ion cyclotron range of frequencies (ICRF) power in fusion devices, control of RF specific interactions with the scrape-off layer plasma and material surfaces is of great importance
The main assumption of the method is that the amplitude of the incoming waves is not changed by the BC
In the illustration of the method in Eqs. (3) – (6), the tangential k is assumed to be equal for fast wave (FW) and slow wave (SW), but this could be generalized
Summary
For applications of ion cyclotron range of frequencies (ICRF) power in fusion devices, control of RF specific interactions with the scrape-off layer plasma and material surfaces is of great importance. A recent general formulation [9] of the SBC provides an effective surface impedance for the interaction of the RF sheath with the waves It enables quantities of interest for material interactions, such as the surface power flux and rectified potential energy available for sputtering, to be calculated. Code data is first postprocessed to obtain the amplitude of the incoming waves Holding this amplitude fixed, the wave equations are solved again, approximately, in the vicinity of the wall sheath, using the SBC.
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