Physics student presentations #2 (summer research in 2023), Thursday (3/21) at 11 am – VDW104

1. “Turbulence and Zonal-Flow Impact in the Madison Symmetric Torus in Quasi-Single Helicity” by Nick Kaipainen, Mentor Zach Williams

Reversed-Field Pinches (RFPs) operating in the Quasi-Single-Helicity (QSH) magnetic geometry exhibit significant improvements in confinement time as compared to standard discharges due to the efficient saturation of large-scale tearing modes. This modification to the magnetic geometry and profiles introduces new instabilities which drive transport. This work focuses on diagnosing the microinstabilities and microturbulence in a non-reversed Madison Symmetric Torus QSH experiment. Local gyrokinetic simulations are conducted with the GENE code to identify the dominant instabilities as ion-temperature-gradient (ITG) and density-gradient-driven trapped-electron-mode (TEM) at core and edge radial locations, respectively. It has been previously observed in the RFP (Williams PoP 2017) that residual tearing fluctuations in RFPs degrade zonal flows; the degree to which this affected turbulence and transport in that work depended on the driving instability. While initial investigations reveal strong zonal flow activity, an ad-hoc magnetic perturbation is employed to model magnetic fluctuations present in the RFP. These fluctuations degrade the zonal flow structure, resulting in a more substantial increase in electrostatic fluxes for the TEM-dominated position than for its ITG counterpart.

2. “Exploring Properties of YBCO Superconductors Using Proton Irradiation” by Joey Fogt, Hope Weeda, Trevor Harrison, and Nolan Miles, Mentor Kyuil Cho

We studied the effect of 600 keV proton irradiation on thin film Cuprate superconductors. Using the Hope Ion Beam Accelerator Laboratory, a 580 nm thick YBCO-1237 sample was subjected to a series of proton irradiations totaling a fluence of 7.2 x 1016 p/cm2. The superconducting critical temperature (Tc ) of the YBCO sample decreased drastically, from 90K towards 0K, while normal state resistivity increased with increasing irradiation dose. These changes in sample properties will be used to discuss fundamental properties of the superconductor.

Leave a comment

Your email address will not be published. Required fields are marked *