Heat-flux footprints for I-mode and EDA H-mode plasmas on Alcator C-Mod

IR thermography is used to measure the heat flux footprints on C-Mod’s outer target in Imode and EDA H-mode plasmas. The footprint profiles are fit to a function with a simple physical interpretation. The fit parameter that is sensitive to the power decay length into the SOL, λSOL, is ~1-3x larger in I-modes than in H-modes at similar plasma current, which is the dominant dependence for the H-mode λSOL. In contrast, the fit parameter sensitive to transport into the private-flux-zone along the divertor leg is somewhat smaller in I-mode than in Hmode, but otherwise displays no obvious dependence on Ip, Bt, or stored energy. A third measure of the footprint width, the “integral width”, is not significantly different between Hand I-modes. Also discussed are significant differences in the global power flows of the Hmodes with “favorable” drift direction and those of the I-modes with “unfavorable” drift direction. PACS: 52.55.Rk, 52.55.Fa, 52.25Fi, 52.70.Kz *Corresponding Author Address: 175 Albany St., Cambridge, MA 02319 USA *Corresponding Author E-mail: [email protected] Presenting Author: James L. Terry Presenting Author E-mail: [email protected] ! "B