DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
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Title	206: Studies of arcing on divertor PFC surfaces
Name:	Dmitry Rudakov rudakov@fusion.gat.com	Affiliation:	University of California, San Diego
Research Area:	Plasma-material Interface	Presentation time:	Not requested
Co-Author(s):	R.P. Doerner, R.A. Moyer, C.P.C. Wong, C. Chrobak, V. Rohde (IPP)	ITPA Joint Experiment :	No
Description:	Arcing may contribute to PFC erosion and dust production in a tokamak. So far arc studies in DIII-D were limited mostly to analysis of campaign-integrated arc tracks on graphite tiles. We propose studying arcing on different material surfaces under controlled plasma conditions using DiMES. The focus will be on W surfaces with and without coatings. Post-exposure analysis of the arc tracks on the samples will be performed by SEM and profilometry. Fast arc imaging and time-resolved arc current measurements will be attempted.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	We propose two 1/2 day experiments. In the first experiment we will expose multi-button DiMES holder with a few different 1/4" buttons including solid W, W coating on graphite, oxidized W, B-coated W, and W with fuzz grown in PISCES. Fast imaging of arcs will be attempted. In the second experiment we will expose a specially built DiMES sample with a W disc partially coated with an isolating layer and isolated from the holder, thus allowing arc current measurements.
Background:	Recent work on ASDEX Upgrade has shown that in a machine with metallic PFCs arcing may be a dominant erosion mechanism. Earlier DiMES experiments in DIII-D showed that W is more prone to arcing than other metals such as V or Be. There is also evidence pointing to isolating layers and fuzz on W surfaces increasing the probability of arcing. We will test arcing on different surfaces using DiMES, focusing on W as the most ITER-relevant material.
Resource Requirements:	2 1/2 day experiments, ELMing LSN H-mode, 5-6 MW of NBI, OSP just inboard of DiMES.
Diagnostic Requirements:	DiMES, fast UCSD camera coupled to a view of DiMES, MDS, IR TV, filterscopes, divertor and core Thomson, SPRED, CER with W lines.
Analysis Requirements:
Other Requirements: