Behavior of lower hybrid waves in the scrape off layer of a diverted tokamak

The goal of the Lower Hybrid Current Drive (LHCD) system on the Alcator C-Mod tokamak is to investigate current profile control under plasma conditions relevant to future devices such as ITER and DEMO. This thesis addresses the behavior of Lower Hybrid (LH) waves in the edge and Scrape Off Layer (SOL) of Alcator C-Mod, a compact, high field, high density, diverted tokamak. The results of coupling experiments over a range of plasma parameters in both Land H-mode plasmas are presented. Experimental observations suggest that power absorption in the SOL (from both Ion Cyclotron Heating and LHCD sources) modifies the density profile in the vicinity of the LH launcher, thereby affecting the coupling of LH waves. An analysis of the damage sustained by the LH launcher also shows absorption of the LH waves in the SOL near the antenna. Estimates of the heat flux sustained by the antenna during high power LHCD are in agreement with measurements of the density and temperature increase on flux tubes intersecting the antenna. Power absorption due to high parallel refractive index modes and collisional absorption are not sufficient to explain the increase in density and temperature of the plasma in front of the antenna. Experimental observations of the LHCD "density limit" for C-Mod are presented.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Wallace, Gregory M

Advisor dc:contributor.advisor

• Ronald R. Parker.

• Nuclear Science and Engineering.

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/1721.1/57694

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/57694