Effects of MHD on DIII-D high-β_pdischarges

The DIII-D high-β_p scenario is often characterized by an internal transport barrier (ITB) at large plasma radius, bolstering core performance while minimizing changes in the plasma edge. Growing evidence suggests MHD can impact the development of ITBs in these discharges, limiting performance. Additionally, many high-performance high-β_p discharges terminate with the onset of a rapidly growing MHD instability. We look to investigate the role of MHD in the scenario trajectories, performance limitations, and ultimate termination of high-β_p discharges with the end goal of optimizing future experiments through MHD avoidance. To achieve this, full-shot kinetic EFITs are developed for a number of DIII-D high-β_p discharges, allowing for detailed analysis of the profile evolution. This will include characterization of the plasma transport using the TRANSP code, as well as MHD stability analysis using GATO. A number of DIII-D high-β_p discharges are analysed for MHD stability, mode behavior, profile evolution, and shot termination. It is seen that MHD can seemingly prevent the growth of large radius ITBs and thus limit performance of the high-β_p discharges, though some discharges do reach high performance without a well-defined ITB, depending on the specific MHD activity observed.