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	195: Correlation of confinement and fluctuations with electron heating in ITER Baseline Scenario
Name:	Robert Pinsker pinsker@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Turbulence & Transport	Presentation time:	Not requested
Co-Author(s):	E.J. Doyle, T.L. Rhodes, C.C. Petty, B. Tobias, B. Grierson, L. Schmitz, G.R. McKee, Z. Yan, L. Zeng, M. Porkolab	ITPA Joint Experiment :	No
Description:	Extend work on dependence on confinement on Te/Ti in conventional ELMing H-mode (C.C. Petty, et al., PRL, Vol. 83, 3661, 1999), QH-mode (Schmitz, et al., 2012), hybrid discharges (Petty, IAEA 2008) to ITER Baseline Scenario discharges. Determine dominant turbulence modes in electron-heating dominated ITER Baseline Scenario.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Basic approach is to create matched pairs of ITER Baseline Scenario discharges, with beam heating only compared with ECH plus NBI. Adjust applied torque in NBI-only case to match rotation speed obtained in ECH case. Study two cases: (1) one with 'normal' levels of toroidal rotation speed (all co beams plus EC compared with adding enough counter-NBI in all NB case to match rotation, and (2) [low rotation] About zero applied torque NBI-only case compared with mostly EC plus about zero applied torque. In each case obtain detailed fluctuation measurements to enable later comparison of observed fluctuations and predicted dominant turbulence (TEM vs ITG, etc.) modes. Measure particle confinement with He puffing technique in all cases. Consider making perturbative measurements with modulation of EC compared with modulation of part of NB power.
Background:	Previous work (see citations in Description) on DIII-D has shown that confinement is very sensitive to Te/Ti in several regimes. In 2012 experiments in which ECH and/or FW direct electron heating was added to ITER Baseline Scenario discharges in order to move towards the dominant electron heating regime, it was observed that incremental confinement tended to be poor with either form of direct electron heating. These results are likely the result of the sensitivity of confinement to the ratio of electron and ion temperatures, as previously studied in detail on DIII-D in other plasma regimes. We propose to investigate explicitly the correlation between confinement and the presumed underlying fluctuations and turbulence in the ITER Baseline Scenario to test this picture. The 2012 work by Schmitz, et al. in QH-mode clearly showed an ITG-to-ETG mode dominated transition upon entrance to the electron-heating dominated regime. Measured fluctuations in Te at mid-radius significantly increased, while the density fluctuations (BES) did not change very strongly. Since ITER discharges will, almost by definition, be electron-heating dominated, it is quite important to study the confinement properties of IBS discharges as we transition from the typical hot-ion types of discharges towards the electron-heating dominated case that is of most interest.
Resource Requirements:	1-2 day experiment. Needs 4-6 NBI sources (no off-axis beams needed, but will need counter-NBI along with mostly co-), all available gyrotrons (at least 6). Helium puffing in some discharges. ITER Baseline Scenario discharges.
Diagnostic Requirements:	In addition to all of the usual profile diagnostics (including EC-hardened profile reflectometers), all of the instruments for observing fluctuations in density and electron temperature. Consider trying to use the imaging EC system as a correlation instrument, to compare with CECE system. BES, DBS, etc.
Analysis Requirements:	Full-blown analysis with GYRO, TGLF, ONETWO, TRANSP to compare characteristics of observed fluctuations and available models.
Other Requirements:	Also submitted to Inductive Scenarios area.