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:20240329T090912Z
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.
\n
\
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
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