Dartmouth Events

Abstract: The Pegasus-III experiment is an ultra-low A solenoid-free ST focused on non-solenoidal plasma startup and sustainment techniques with helicity injection and a microwave heating and CD system. To enable operation in overdense plasmas, a 28 GHz system capable of both Electron Bernstein Wave (EBW) and EC heating will be implemented. The synthetic aperture microwave imaging diagnostic (SAMI) and Dual Polarized Horn Radiometer (DPHR) are being used to carry out the first exploration of EBW emission measurements of local helicity injection (LHI)plasmas to assist in the development of this system. Measurements of microwave power emitted from LHI plasmas have been made and promising plasma scenarios for the confirmation of mode conversion windows have been identified. Characterization of these power measurements is ongoing, as is the exploration of plasma conditions that could allow best imaging of EBW mode conversion windows on Pegasus-III. Additionally, simulations of EBW injection and current drive have shown power absorption in the core for 0.6 T Pegasus-III plasma and driven currents up to 3.3kA for 150 kW of injected power. Collisional damping effects were seen to reduce localization of power absorption, and for microwave injection during active helicity injection, density and magnetic field fluctuations from electron streams were modeled to decrease mode conversion efficiency up to 50%. The microwave system supported by this work will allow direct tests of synergistic improvements to helicity injection initiation and ramp-up scenarios by microwave injection.

Hosted by Dartmouth Graduate Student Sarah Peery 

Zoom Link: https://dartmouth.zoom.us/j/99960465228