Global momentum confinement times in Alcator C-Mod H- and I- regime plasmas

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.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2014

Author dc:creator

• Victora, Michelle (Michelle M.)

Advisor dc:contributor.advisor

• Bruno Coppi and John Rice.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/92675

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/92675