Tuesday, October 20, 2020
As ion cyclotron radio frequency range (ICRF) heating becomes increasing used in fusion devices, the urgency of predicting and mitigating impurity generation that arises from it becomes increasingly important. In the ICRF regime, rectified RF sheaths are known to form at antenna and material edges that influence negative effects like sputtering and a decrease in heating efficiency. Much of the focus of RF sheaths has been on the “near-field,” however experimental evidence shows that “far-field” sheaths also play an important role in enhancing the influx of impurities. Given the size of the sheath relative to the scale of the device, it can be approximated as a boundary condition (BC). Electromagnetic field solvers in the ICRF regime typically treat material boundaries as perfectly conducting, thus ignoring the effect of the RF sheath. Here we describe progress on implementing a model for the RF sheath based on the a finite impedance sheath BC formulated by J. Myra et al. 2015 which provides a representation of the RF rectified sheath including capacitive and resistive effects. This research will discuss the development of a parallelized cold-plasma wave equation solver, “Stix," that implements this non-linear sheath impedance BC through the method of finite elements aimed at investigating the fundamental behavior of far-field sheaths.
Zoom easy link: https://mit.zoom.us/j/97594071409?pwd=RE9iKzNwMFNKN1ZQTEJCaVFYUmd2dz09