Global momentum confinement times in Alcator C-Mod H- and I- regime plasmas
Author(s)Victora, Michelle (Michelle M.)
Massachusetts Institute of Technology. Department of Physics.
Bruno Coppi and John Rice.
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Using a spatially-resolving x-ray spectrometer system, the toroidal rotation velocity in Alcator C-Mod plasmas is measured and analyzed. At the L-H and L-I transition, there is a co-current movement in the toroidal rotation velocity.The propagation of this rotational velocity from the edge to the core of the torus was measured following the L- to H- and L- to I-mode transitions. A hyperbolic tangent fit was used to determine a single variable for rise time in rotational velocity. The hyperbolic tangent fit parameter acts as a proxy for the global momentum confinement time, which is then compared to other plasma parameters. Through this compaxison, we found an decrease in rise time in correlation with increasing density(n)/current(I), particularly distinctive in the range of 1-2.5 x 10²⁰ (MA x m³)-¹. Due to a lack of overlap in density between I- and H-mode, we find this may be indicative of an overall decrease in rise time between L- to I- and L- to H-mode transitions. In order to explore this possibility, we must achieve I-mode runs with the same current and density as Hmode to determine if there is still a decrease between the two transitions.
Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 43-45).
DepartmentMassachusetts Institute of Technology. Department of Physics.
Massachusetts Institute of Technology