Scaling of the power exhaust channel in Alcator C-Mod

• Main Authors: Rowan, W. L. (Author), Wurden, G. (Author), Labombard, Brian (Contributor), Terry, James L. (Contributor), Hughes, Jerry W. (Contributor), Brunner, Daniel Frederic (Contributor), Payne, Joshua E. (Contributor), Reinke, Matthew Logan (Contributor), Cziegler, Istvan (Contributor), Granetz, Robert S. (Contributor), Greenwald, Martin J. (Contributor), Hutchinson, Ian H. (Contributor), Irby, James Henderson (Contributor), Lin, Yijun (Contributor), Lipschultz, Bruce (Contributor), Ma, Yunxing (Contributor), Marmar, Earl S. (Contributor), Tsujii, Naoto (Contributor), Wallace, Gregory Marriner (Contributor), Whyte, Dennis G. (Contributor), Wolfe, Stephen M. (Contributor), Wukitch, Stephen James (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Nuclear Science and Engineering (Contributor), Massachusetts Institute of Technology. Department of Physics (Contributor), Massachusetts Institute of Technology. Plasma Science and Fusion Center (Contributor)
• Format: Article
• Language: English
• Published: American Institute of Physics, 2011-12-09T18:05:59Z.
• Subjects: Article
• Online Access: Get fulltext

Parametric dependences of the heat flux footprint on the outer divertor target plate are explored in EDA H-mode and ohmic L-mode plasmas over a wide range of parameters with attached plasma conditions. Heat flux profile shapes are found to be independent of toroidal field strength, independent of power flow along magnetic field lines and insensitive to x-point topology (single-null versus double-null). The magnitudes and widths closely follow that of the "upstream" pressure profile, which are correlated to plasma thermal energy content and plasma current. Heat flux decay lengths near the strike-point in H- and L-mode plasmas scale approximately with the inverse of plasma current, with a diminished dependence at high collisionality in L-mode. Consistent with previous studies, pressure gradients in the boundary scale with plasma current squared, holding the magnetohydrodynamic ballooning parameter approximately invariant at fixed collisionality-strong evidence that critical-gradient transport physics plays a key role in setting the power exhaust channel.
United States. Dept. of Energy (Award DE-AC52-06NA25396)
United States. Dept. of Energy (Coop. Agreement DE-FC02-99ER54512)