Speaker: Dr. Marien Simeni, University of Minnesota
Title: "Resonant and Non-Resonant E-FISH-based Electric Field Measurements in Low to High Pressure Plasmas"
Abstract: Spatio-temporally resolved electric field (E) vector measurements are a cornerstone for advancing nearly all sub-fields of plasma physics. Precise E-field data is critical for validating fundamental sheath theories across diverse collisionality regimes, analyzing surface streamer and ionization wave dynamics, and understanding complex phenomena such as edge-localized mode (ELM) instabilities in tokamaks or magnetic reconnection events. Despite this importance, non-intrusive measurements with high sensitivity and wide dynamic range remains a significant diagnostic challenge. In this talk, we present a novel laser-based diagnostic approach that provides exceptional E-field sensitivity across multiple orders of magnitude (< 1 V/cm to > 10 kV/cm). We demonstrate the versatility of this technique in both low- and high-pressure environments, effectively bridging the gap between vacuum-based and atmospheric-pressure plasma studies. A key highlight of this work is the simultaneous characterization of gas-phase transients and surface electric fields during plasma-material interactions. By resolving the coupling between the plasma bulk and surface charging in real-time, this diagnostic offers a new tool for probing the complex boundary layers inherent in plasma processing and fusion devices. We anticipate that the increased accessibility and straightforward implementation of this approach will enable widespread application across the plasma science community.
Bio: Marien Simeni is a Richard and Barbara Nelson Assistant Professor at the Mechanical Engineering Department of the University of Minnesota (UMN), where he started in April 2022. His research group focuses on the development of ultrafast laser diagnostics to unravel kinetic mechanisms and energy transfers in non-equilibrium electrical discharges and laser-produced plasmas as well as in reactive flows. Marien received his B.S. in physics from Ecole Normale Superieure Cachan and Université Pierre et Marie Curie (France) in 2009, his M.S. in aerospace engineering from Ecole Centrale Paris (France) in 2011 and his Ph.D. in aerospace engineering from the same institution in 2015. He subsequently held a postdoctoral position at the Ohio State University (2015-2018), a research associate position at UMN (2018-2020) and an associate research physicist position at the Princeton Plasma Physics Laboratory (2020-2022). Marien is a recipient of the 2024 Department of Energy (DOE) Early Career Award and was the inaugural Robert Ellis Jr. Fellow at PPPL in 2020.
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Seminar Access: In-person seminars are only available to CU ID holders. Non-Columbia affiliates can contact [email protected] if you'd like the seminar Zoom link.