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	34: Electron Critical Gradient and Heat Pinch
Name:	Clinton (Craig) Petty petty@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Turbulence & Transport	Presentation time:	Not requested
Co-Author(s):	T. Luce, S. Smith, C. Holland	ITPA Joint Experiment :	No
Description:	Explore the relation between the critical gradient in the electron temperature and the electron heat pinch. Use heat pulse modulation to separate the "power balance" heat flux into its conductive and convective components. Determine if an inward electron heat pinch exists for the low gradient cases. Use plasmas previously found to give inward electron heat fluxes, i.e., high density and low plasma current L-mode plasmas. We want to document as many fluctuations as possible.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	(1) Establish L-mode plasma with Ip=500 kA and density=3e+19 m^-3. Use occasional short beam pulses to measure ion profiles. (2) Inject all 6 gyrotrons at rho=0.6. Modulate one gyrotron at 25 Hz. (3) Shot by shot, move one gyrotron from rho=0.6 to rho=0.4. (4) Document each case with fluctuation diagnostics such as CECE and DBS. (5) We can set up a "second" phase of the experiment to add NBI, as was done in 2011. (6) If time permits, repeat at a larger rho value (0.6-0.8).
Background:	This proposal builds upon the electron critical gradient experiment led by Jim DeBoo in 2011. By combining "power balance" heat flux with heat pulse propagation, the steady-state conductive and convective components of the electron heat flux could be determined. This allowed an electron critical gradient to be identified that is in agreement with fluctuation measurements and GYRO calculations. For both the rho=0.4 and rho=0.6 cases, there was evidence for a small heat pinch at the lowest electron temperature gradient. In this experiment we will change the plasma conditions to be more favorable for making electron heat pinches by increasing the density (which increases the ion-electron heat exchange) and lowering the plasma current (which reduces the ohmic heating). It is expected that this experiment will find clear evidence for an inward electron heat pinch, especially then the electron temperature is below the critical gradient.
Resource Requirements:	ECH: Desire all 6 gyrotrons. NBI: Need 30LT, 330LT, 150LT sources.
Diagnostic Requirements:	All profile diagnostics, including density profile reflectometry. All fluctuation diagnostics.
Analysis Requirements:	Besides standard transport analysis, will need TGLF/GYRO calculations of the electron critical gradient, and TGLF simulations of the temperature profiles.
Other Requirements: