Non-Perturbative Mapping of Inverted Sheaths in Low-Temperature Plasmas

This award supports development of a novel quantum sensing diagnostic for studying plasma properties near solid surfaces. Plasmas are used in technologies that matter in everyday life, from computer chip manufacturing, to spacecraft propulsion systems, to potential new energy production facilities. When a plasma touches a solid surface, a very thin but complex electrical layer called a plasma sheath is formed. The properties of such sheaths and the interaction between the plasma and a surface are not yet fully understood. This project will develop new laser-based measurement methods to study how plasma sheaths form and how they may be controlled. The gained knowledge will help make important technologies more efficient, more reliable, and longer-lasting, with benefits for areas ranging from semiconductor manufacturing to fusion energy research. This award will also support the training of graduate and undergraduate researchers at West Virginia University, the development of a new advanced undergraduate laboratory course module in plasma physics, and expand outreach and opportunity to students from rural and underserved communities across West Virginia. Plasma–boundary regions will be investigated in this work to determine how electron emission from a surface modifies ion flows, electric fields, and potential structures from the plasma bulk through the plasma sheath to the surface. Particular attention will be given to strongly emitting boundaries, where transitions from classical to space-charge-limited and inverted sheath structures are predicted but have been only sparsely examined experimentally. High-fidelity, nonintrusive, spatially resolved measurements will be obtained by combining laser-induced fluorescence to measure ion velocity distributions with quantum beat spectroscopy to map electric fields and infer potential profiles without the use of intrusive probes. These measurements will be used to determine whether inverted sheath structures form under standard low-temperature plasma conditions, to identify how ion flows to a surface are influenced by tunable electron emission, and to quantify whether strongly emitting boundaries can be controlled to minimize ion flux under conditions relevant to plasma applications. The resulting data are expected to test long-standing sheath theory, validate and inform models of plasma–material interaction, electric propulsion, and low-temperature plasma processing, and establish a broadly applicable diagnostic toolkit for nonintrusive boundary measurements across a range of plasma environments. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2606272 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Thomas Steinberger | Institution: West Virginia University Research Corporation, MORGANTOWN, WV | Award Amount: $633,833 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2606272 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2606272.html