The electron current density that escapes from multi-emissive magnetized sheaths constitutes a critical quantity in modern evaluations of ITER plasma-facing component (PFCs) deformation due to macroscopic melt motion. During ITER edge-localized modes, electrons can be emitted from the PFCs through field assisted thermionic emission, secondary electron emission (SEE) and electron backscattering (EBS). In the case of space-charge limited sheaths, an analytic semi-empirical expression is available for the total escaping current density. Here, an analytic empirical model is proposed for the unexplored case of classical monotonic sheaths comprising (i) an existing semi-empirical description of prompt re-deposition in the presence of surface electric fields based on particle orbit simulations; (ii) existing analytic expressions for the SEE and EBS currents as a function of the electron temperature; (iii) a new semi-empirical relation between the total electron emission yield and surface electric field; (iv) a novel correlation for the magnitude of the surface electric field in the absence of electron emission. The new predictive model is valid for arbitrary magnetic field inclination angles and is benchmarked against systematic particle-in-cell simulations.
Slide-away distributions and relevant collective modes in high-temperature plasmas