" Gyrokinetic analysis of microinstability-driven dynamics in a QSH environment on the Madison Symmetric Torus" by Matt Stowe,
mentor Zach Williams, 
2024 Summer Research

Reversed-Field Pinches operating in Quasi-Single-Helicity (QSH) geometry exhibit significantly improved confinement time compared to standard discharges due to efficient saturation of large scale tearing modes. However, this modified geometry introduces new instabilities that can drive transport as well as high-frequency parallel magnetic field fluctuations, which have been directly observed in experiments. This work focuses on categorizing these fluctuations through computational analysis of the microinstabilities and microturbulence present in a non-reversed Madison Symmetric Torus QSH experiment. Local gyrokinetic simulations are conducted using the new GENE 3.0 code to advance existing studies that identified ion-temperature-gradient and trapped-electron-mode instabilities present in the core and edge regions of the device respectively. Microinstability-driven transport is thoroughly categorized and discussed, with particular attention given to the role of zonal flows and sensitivity to tearing-mode-like fluctuations. Parallel magnetic field fluctuations are also included in the simulations for more direct comparison to experimental data.