BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:2 UID:UW-Physics-Event-5005 DTSTART:20190422T170500Z DURATION:PT1H0M0S DTSTAMP:20260419T084828Z LAST-MODIFIED:20190403T162928Z LOCATION:2241 Chamberlin Hall SUMMARY:Diagnosing impurity transport in the scrape-off layer of DIII- D using outer-midplane collector probes with isotopically enriched tun gsten tracer particles\, Plasma Physics (Physics/ECE/NE 922) Seminar\, Professor David C. Donovan\, University of Tennessee-Knoxville (UTK) DESCRIPTION:The impurity transport chain begins at the plasma facing c omponent (PFC) target\, connects through the edge (Scrape-Off Layer (S OL) and Divertor) plasma\, and finally contaminates the core plasma. U nderstanding the nature of impurity transport in the SOL is therefore of crucial importance to control core contamination\; however\, the SO L link in the transport chain is the most weakly understood due to dia gnostic limitations. CPs provide the unique capability to sample the i mpurity content of the SOL and their use is greatly enabled by high se nsitivity material characterization techniques and interpretive modeli ng tools. Two isotopically distinct sources of W were installed on the lower divertor for the DIII-D MRC\, which allowed the W impurities co llected by the mid-plane CPs to be traced back to the poloidal locatio n on the divertor from which they came. The CPs were combined with W s ource spectroscopy to determine a leakage proxy for impurities escapin g the divertor and reaching the SOL. Results will be presented demonst rating that impurity leakage from the outer strike point increases nea rly linearly with power across the separatrix. Experiments varying the ELM frequency identified that leakage from the far-target region is r educed significantly as ELM size decreases. The DIVIMP-OEDGE-WALLDYN c ode suite was utilized as an interpretive modelling tool for the edge plasma region. Experimental results have been obtained that are consis tent with computational models hypothesizing an accumulation of impuri ties in the crown region of the SOL created by ion temperature gradien ts. This unique combination of impurity exposure capabilities\, SOL di agnostic coverage\, ex-situ material characterization\, and interpreti ve modeling tools have provided a potent framework with which to bette r elucidate the SOL link in the impurity transport chain.
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\ n*Work supported by US DOE under DE-SC0016318\, DE-SC0019256\, DE-AC05 -00OR22725\, DE-FG02-07ER54917\, DE-FC02-04ER54698\, DE-AC04-94AL85000 . URL:https://www.physics.wisc.edu/events/?id=5005 END:VEVENT END:VCALENDAR