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Events During the Week of December 15th through December 22nd, 2019

Monday, December 16th, 2019

No events scheduled

Tuesday, December 17th, 2019

Plasma Physics (Physics/ECE/NE 922) Seminar
Lithium Plasma Facing Component Characterization and Plasma Performance for the Lithium Tokamak eXperiment-Beta
Time: 1:30 pm - 2:30 pm
Place: B343 Sterling Hall
Speaker: Anurag Maan, University of Tennessee, Knoxville
Abstract: Lithium is an attractive low-Z plasma facing component (PFC), due to its ability to reduce ra-diative power loss and recycling by retaining hydrogen. Lithium coatings on high-Z plasma facing components (PFCs) in the Lithium Tokamak eXperiment (LTX) led to flat temperature profiles. The flat temperature profiles were observed along with a hot low density edge, implying a broad, collisionless Scrape-Off Layer (SOL). Additionally, in-vacuo analysis of PFCs indicated that evapo-ratively deposited lithium coatings appeared to be oxidized, while the ability to achieve good plasma performance was retained. Theory attributes flat temperature profiles to low recycling walls, which was assumed to be due to hydrogen binding with elemental lithium to form lithium hydride. The presence of oxidized lithium, however, raises questions regarding the exact mechanism of hydrogen retention in LTX. To investigate these questions, a new Sample Exposure Probe (SEP) for detailed in-vacuo analysis of PFC samples was designed and commissioned for LTX-β. The SEP is equipped with a vacuum suitcase capable of transporting samples representative of LTX-β outer mid-plane PFCs under high vacuum to a stand-alone high resolution X-ray Photoelectron Spectroscopy (XPS) system. Surface analysis using the SEP was performed with sufficient energy resolution to identify for the first time, the compounds that grow on evaporative lithium coatings inside a tokamak. This was the first demonstration that a vacuum suitcase can afford a solution that is simpler in design and affords more flexibility than building material characterization test stands for installation on a tokamak. The results indicate that Li2O and LiOH are prime surface constituents of Li PFCs. Their presence substantiates the hypothesis that lithium oxide grows on elemental lithium before the growth transitions to lithium hydroxide for LTX-β like vacuum conditions. It is further indicated that Li2O improves plasma performance in comparison to LiOH by both sequestering oxygen and increasing hydrogen retention.
Host: Karsten McCollam
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Wednesday, December 18th, 2019

Thesis Defense
Sam Neyens PhD Thesis Defense
Time: 9:30 am
Place: 5280 Chamberlin Hall
Speaker: Sam Neyens, Physics PhD Graduate Student
Abstract: In pursuit of quantum hardware: Investigations of gated quantum dots in Si/SiGe heterostructures
Host: Mark Eriksson, Faculty Advisor
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Thursday, December 19th, 2019

No events scheduled

Friday, December 20th, 2019

No events scheduled