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	111: Dependence of I-mode on current direction and heating mix
Name:	Amanda Hubbard hubbard@psfc.mit.edu	Affiliation:	Massachusetts Institute of Technology
Research Area:	ELM Control	Presentation time:	Requested
Co-Author(s):	Dennis Whyte, Anne White (MIT), Max Fenstermacher (LLNL), Alberto Loarte (ITER Organization). George McKee (U. Wisc).	ITPA Joint Experiment :	Yes
Description:	The I-mode regime is extremely attractive for fusion in that it combines a thermal barrier and high energy confinement with high particle transport, preventing accumulation of impurities and removing the need for ELMs. Multi-machine studies are being carried out through the ITPA (TC-18 and 19, PEP-31). It is under consideration for ITER. However, issues remain for the extrapolation to ITER. The key concern is that the regime is usually obtained in the unfavorable drift configuration, which for ITER means reversing field and current. This would mean that NBI is in the counter direction. The same would be true on JET, which for this reason has not yet explored I-mode. At the recent ITPA meeting, Alberto Loarte suggested that D3D could play a critical role in investigating dependences on current direction, and of heating source and direction. It is unique in being able to independently vary Ip and Bt direction; C-Mod, AUG and JET all need to maintain the same helicity for various technical reasons. It also has a flexible heating mix including ECH and co and counter NBI. We therefore propose to compare I-mode access and properties with different Ip directions, and different heating sources. A positive outcome would motivate future experiments on JET, and support the development of the regime for ITER. This experiment should follow the establishment of a robust I-mode regime (see proposals from Dennis Whyte and Anne White). It will support the FY13 JRT. Experimental details will be added in the following sections.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	This experiment should follow successful completion of Dennis Whyte??s Idea 83 and/or Anne White??s idea 37, demonstrating robust I-mode with LSN, reversed BT, standard Ip (co-NBI). We will use a fixed shape and parameter set from that experiment. The experiment will be done in two parts, on different days (order and priority TBD): Day 1: Reversed Ip, keeping everything else fixed. (ie counter NBI). This will also have the advantage that standard helicity optimizes the BES spatial resolution, important for GAM measurements (see idea #362) 1.Assess power range, performance, pedestal properties and compare with above. 2.Vary NBI direction. Co vs counter vs balanced/mix. Based on July expts we expect to need 2-3 MW to get I-mode. 3.Compare balanced NBI with predominantly ECH. Day 2: Normal Ip, but reversed Ip, as on XP37. Repeat steps 2 and 3 above. Taken together, these experiments will assess and separate effects of torque and of fast ion losses.
Background:	I-mode is a stationary, high performance regime without ELMs ?? attractive in many respects for fusion, including ITER. It has been robustly obtained over wide parameter ranges on C-Mod, and also observed on AUG over several years. Initial assessments of extrapolation to ITER, by Dennis Whyte, look promising [See Marmar APS 2011 and Hubbard IAEA 2012 talks]. To obtain the unfavorable drift configuration, ITER would need to use Reversed BT and Ip, LSN. The ITER Team is interested in assessing I-mode. However, the biggest potential obstacle is that reversed Ip would mean counter-NBI. It is not clear how this would affect I-mode access and performance. D3D is UNIQUELY capable to assess this question. It can run - Different Ip directions with SAME BT, and divertor geometry, and - Different heating mixes (ECRH, co vs counter or balanced) with SAME Ip and BT direction. Other devices (C-Mod, AUG, JET) are restricted to a single helicity, meaning that Ip and Bt need to be changed together; changing Ip direction implies a major change in the configuration (USN vs LSN). Also, C-Mod has no NBI and AUG and JET only one direction. At the recent ITPA meeting, IO (Loarte) suggested and group agreed that this D3D experiment be a priority in 2013 (for TC-19, PEP-31). If results are positive, will motivate a JET experiment with counter-NBI in 2014.
Resource Requirements:	NBI, both co and counter. ECH. 3 MW each system.
Diagnostic Requirements:	Top priority on edge profile diagnostics, and edge and core fluctuation diagnostics.
Analysis Requirements:	--
Other Requirements:	--