Characterization of ELM Pacing via Vertical Kicks on DIII-D

This work presents an in-depth analysis of Edge Localized Mode (ELM) triggering via vertical kicks on DIII-D. Vertical kicks or plasma oscillations have been considered a viable method of ELM pacing in future fusion devices. Unlike other ELM pacing methods, vertical kicks do not require additional hardware to induce magnetic perturbations or to inject pellets. It has been found that ELMs in DIII-D are triggered while moving the core plasma towards the X-point. The frequency of vertical kicks has been set to 20 Hz; Accordingly, the ELM frequency has increased from ~5 Hz, the natural ELM frequency in similar DIII-D discharges, to 20 Hz. The peak heat flux to the outer divertor from each ELM decreased by more than a factor of 2 when triggered by vertical kicks. Line-averaged effective ion charge near the plasma midplane decreased during the kicks, indicating that kicks may cause increased flushing or exhaust of impurities. Increased impurity flushing is important to remove high-Z impurities and helium ash in a burning plasma.