Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas
Name
White_Non-local heat.pdf
Size
3.83 MB
Format
Adobe PDF
Checksum (MD5)
eab3965db52cc23ee00999815d19e8f3
Author(s)
Rice, John E.
Sun, H. J.
Reinke, Matthew Logan
Howard, Nathaniel Thomas
Mikkelson, D.
Hubbard, Amanda E.
Chilenski, Mark Alan
Walk Jr, John R.
Ennever, Paul Chappell
Porkolab, Miklos
Date Issued
August 2014
Journal
Nuclear Fusion
Publisher
Institute of Physics/International Atomic Energy Agency
Citation
Gao, C., J.E. Rice, H.J. Sun, M.L. Reinke, N.T. Howard, D. Mikkelson, A.E. Hubbard, et al. “Non-Local Heat Transport in Alcator C-Mod Ohmic L-Mode Plasmas.” Nuclear Fusion 54, no. 8 (June 26, 2014): 083025.
Version
Original manuscript
Abstract
Non-local heat transport experiments were performed in Alcator C-Mod ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF2) injection. The non-local effect, a cooling of the edge electron temperature with a rapid rise of the central electron temperature, which contradicts the assumption of 'local' transport, was observed in low collisionality linear ohmic confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either by a fast drop of the core diffusivity, or the sudden appearance of a heat pinch. In high collisionality saturated ohmic confinement (SOC) regime plasmas, the thermal transport becomes 'local': the central electron temperature drops on the energy confinement time scale in response to the edge cooling. Measurements from a high resolution imaging x-ray spectrometer show that the ion temperature has a similar behaviour as the electron temperature in response to edge cooling, and that the transition density of non-locality correlates with the rotation reversal critical density. This connection may indicate the possible connection between thermal and momentum transport, which is also linked to a transition in turbulence dominance between trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. Experiments with repetitive cold pulses in one discharge were also performed to allow Fourier analysis and to provide details of cold front propagation. These modulation experiments showed in LOC plasmas that the electron thermal transport is not purely diffusive, while in SOC the electron thermal transport is more diffusive like. Linear gyrokinetic simulations suggest the turbulence outside r/a = 0.75 changes from TEM dominance in LOC plasmas to ITG mode dominance in SOC plasmas.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Terms of Use
Creative Commons Attribution-Noncommercial-Share Alike
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1088/0029-5515/54/8/083025
