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	37: Identification of I-mode through simultaneous core and edge turbulence measurements
Name:	Anne White whitea@mit.edu	Affiliation:	Massachusetts Institute of Technology
Research Area:	Turbulence & Transport	Presentation time:	Requested
Co-Author(s):	D. G. Whyte, M. Fenstermacher, A. E. Hubbard, J. Hughes	ITPA Joint Experiment :	No
Description:	This experiment follows up on progress made in creating I-modes at DIII-D, MP #2012-93-04 I-mode on DIII-D will be created, e.g. based on target shots such as 149908, and changes in core and edge turbulence will be documented in order to identify I-mode. C-Mod measurements indicate that is it a combination of reductions in core and edge turbulence, rather that WCM appearance, that are clear indicators of I-mode [White TTF 2012] (in addition to increased in confinement with Pinj, and formation of Te-pedestals and not ne-pedestals).	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Target shots are The DIII-D I-mode experiment proposed here will consist of 1-day of run time. The first half day will consist of a wide parameter scan in current, density,and heating power to determine the conditions most favorable for I-mode (starting of course near the "best case" parameters from 2012). The second half day will consist of many dedicated repeat shots of "best I-mode targets" in order to document as clearly as possible fluctuations measured with BES, CECE, DBS, PCI, etc. It will be essential to target I-mode candidates with the proper density, B-field and NBI arrangement (e.g. on axis 150 L) to optimize fluctuation measurements. This was not done in the past exploratory experiments due to time constraints.
Background:	ELMs have the potential to destroy the first wall of ITER or a reactor. Many ELM control and mitigation techniques are being explored, but it is fruitful to consider an operating scenario that simply does not require ELMs occur. QH-mode and I-mode are two such candidate regimes. DIII-D is well poised to explore and promote such alternative regimes for ITER and future reactors. I-mode, in contrast to QH-mode, has not been thoroughly explored on DIII-D and this proposed experiment will build on experience gained from MP #2012-93-04 in order to 1) create I-mode and 2) unambiguously identify it as such via detailed core and edge turbulence measurements. This experiment follows up on progress made in creating I-modes at DIII-D, MP #2012-93-04 "Exploration of I-mode operating space", that was led by Dennis Whyte last summer. It was observed at DIII-D that high confinement plasmas with a temperature pedestal but no density pedestal could be created and sustained. Additionally, as input power was increased, confinement did not degrade. However, there was no evidence of the edge localised Weakly-Coherent Mode (WCM) on edge midplane fluctuation diagnostics, which is taken to be a signature of I-mode at C-Mod [Whyte NF 2010]. Recently at C-Mod, there is mounting evidence collected during JRT 2012 experiments that I-modes can occur without clear WCM features observed at the outboard midplane, and in fact, other changes in edge and core turbulence simultaneously may in fact be clearer signatures of I-mode. Using the extensive set of core and edge fluctuation diagnostics at DIII-D we can probe the changes in both edge and core turbulence that occur at the L-I mode transition, thus providing better evidence that in fact I-mode has been produced at DIII-D and at C-Mod in cases when the WCM is not clearly visible in the measurements. For more details, please see slides presented at July 26th 2012 805 meeting.
Resource Requirements:	Experimental set-up as on 149908, but with ON AXIS 150L NBI for optimum BES measurements, and density scan to optimize DBS measurements.
Diagnostic Requirements:	Full profile diagnostics where possible (Thomson, ECE, CER, MSE...). Full turbulence suite (BES, CECE, DBS, PCI, edge probes, etc.)
Analysis Requirements:	Profile analysis, CER, MSE, turbulence data, TRANSP, ONETWO, TGLF, BOUT++, EPED...etc.
Other Requirements:	--