Sherwood 2015

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Investigating the Effects of the X-Divertor Geometry on Detachment Control and Edge Pedestal Integrity in DIII-D

Author: Brent M. Covele
Requested Type: Poster Only
Submitted: 2015-01-19 13:30:52

Co-authors: M.Kotschenreuther, P. Valanju, S. Mahajan. A. Leonard, A. Hyatt, D. Thomas

Contact Info:
University of Texas at Austin
1 University Station
Austin, Texas   78712
United States

Abstract Text:
Recent X-Divertor (XD) experiments on DIII-D were designed to determine the effects of enhanced flux expansion, connection length, and Divertor Index > 1 on divertor heat flux reduction and detachment control. Obtaining the XD geometry with the DIII-D shaping coils posed its own set of control challenges, which were alleviated beforehand with the use of the TokSys controls code. As a result, XDs were successfully created, both at high triangularity on the lower floor, and at lower triangularity on the lower shelf, so that the divertor could be analyzed with the Divertor Thomson Scattering (DTS) diagnostic. Standard divertor (SD) geometries, with Divertor Index very near 1, were also created for comparison purposes. All four types of divertor configurations were puffed deep into detachment (defined here by very low electron temperatures at the targets). Initial comparisons between geometries are made regarding (1) the onset of detachment near the target, (2) edge pedestal pressure integrity in deep detachment, (3) heat flux reduction, and (4) the relationship between upstream electron density and gas puffing rate. Experimental results are also compared to SOLPS 5.1 simulations to assist in determining the relevant physical mechanisms at work in the divertor at detachment.


March 16-18, 2015
The Courant Institute, New York University