DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
Print this page

Print this page
Title	209: RMP ELM-Control for Snowflake Configurations
Name:	Ilon Joseph joseph5@llnl.gov	Affiliation:	Lawrence Livermore National Laboratory
Research Area:	Torkil Jensen Award	Presentation time:	Requested
Co-Author(s):	SA Allen, BI Cohen, RH Cohen, ME Fenstermacher, E Koleman, TD Rognlien, DD Ryutov, VA Soukhanovskii, MV Umansky	ITPA Joint Experiment :	No
Description:	The combination of both the snowflake divertor and the use of external coils to generate RMP-ELM suppression could be a game-changer for future tokamak fusion reactors. This configuration possesses the unique ability to mitigate both steady-state and transient heat fluxes. The snowflake divertor has significant advantages over the standard divertor in its ability to couple to RMPs. Because the snowflake has stronger magnetic shear and longer connection length: (i) the rational surfaces on which RMPs act are more closely packed near the separatrix (ii) the magnetic stochasticity criterion of island overlap is easier to satisfy (iii) it may be easier to place an island sufficiently close to the pedestal to suppress ELMs, e.g., to suppress ELMs more quickly after initiation of RMP coil currents (iv) the Kolmogorov length can be made much shorter than the connection length, which should lead to a relatively large edge region that is affected by enhanced effective perpendicular diffusion. For this experiment, it is important to clearly characterize the properties of the snowflake pedestal, including ELM stability and the relative magnitude of ExB and diamagnetic rotation. It is important to determine whether the perpendicular electron flow can be made to vanish sufficiently close to the steep gradient region of the pedestal.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Reproduce the successful snowflake discharges as an experimental control (with C-Coil error field control). Starting from this configuration, apply n=2 and 3 RMPs generated by I-Coils. Ramp I-coil current to 4KA-t to determine whether ELM mitigation or suppression can be observed. Use hi-res TS and CER to characterize pedestal before and after coils are energized.edestal before and after coils are energized.
Background:	Initial snowflake-minus divertor studies in DIII-D indicated that ELM energy was universally reduced in the snowflake configuration, and ELM peak heat flux in the divertor outer strike point region was significantly reduced in the snowflake configuration with deuterium seeding. For a recent review of RMP-ELM control, see I. Joseph, Contrib. Plasma Phys. 52, 326 (2012).
Resource Requirements:	Snowflake PCS, I-Coils, ,C-Coils
Diagnostic Requirements:	High-res pedestal profile diagnostics, core and edge impurity spectroscopy (CXR), divertor diagnostics (DTS, IR TV, spectroscopy)
Analysis Requirements:	TRANSP, EFIT, ELITE, UEDGE, TRIP3D, EMC3
Other Requirements: