BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:4 UID:UW-Physics-Event-5252 DTSTART:20191217T193000Z DTEND:20191217T203000Z DTSTAMP:20260415T061046Z LAST-MODIFIED:20191216T144139Z LOCATION:B343 Sterling Hall SUMMARY:Lithium Plasma Facing Component Characterization and Plasma Pe rformance for the Lithium Tokamak eXperiment-Beta\, Plasma Physics (Ph ysics/ECE/NE 922) Seminar\, Anurag Maan\, University of Tennessee\, Kn oxville DESCRIPTION:Lithium is an attractive low-Z plasma facing component (PF C)\, due to its ability to reduce ra-diative power loss and recycling by retaining hydrogen. Lithium coatings on high-Z plasma facing compon ents (PFCs) in the Lithium Tokamak eXperiment (LTX) led to flat tempe rature 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 t hat evapo-ratively deposited lithium coatings appeared to be oxidized\ , while the ability to achieve good plasma performance was retained. T heory 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 co mmissioned for LTX-β. The SEP is equipped with a vacuum suitcase capa ble of transporting samples representative of LTX-β outer mid-plane P FCs under high vacuum to a stand-alone high resolution X-ray Photoelec tron Spectroscopy (XPS) system. Surface analysis using the SEP was per formed with sufficient energy resolution to identify for the first ti me\, 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 flexib ility than building material characterization test stands for installa tion on a tokamak. The results indicate that Li2O and LiOH are prime s urface constituents of Li PFCs. Their presence substantiates the hypot hesis 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 compari son to LiOH by both sequestering oxygen and increasing hydrogen retent ion. URL:https://www.physics.wisc.edu/events/?id=5252 END:VEVENT END:VCALENDAR