Density Profile Measurements in LDX
Author: Alexander C. Boxer
Requested Type: Poster Only
Submitted: 2006-12-18 16:09:28
Co-authors: J.Kesner, D.T.Garnier, J.L.Ellsworth
Contact Info:
MIT
175 Albany Street NW17-217
Cambridge, MA 02139
USA
Abstract Text:
Measuring and understanding the evolution of the plasma density profile is an important goal for the Levitated Dipole Experiment (LDX). We have constructed a 4-channel microwave interferometer (center frequency 60GHz) that allows us to reconstruct the density profiles of LDX plasmas. The assumptions of a plasma with an equal number of particles per flux tube results in a density profile that is highly peaked and scales with radius as 1/r^4. Initial measurements point to an even steeper profile. Presently, the principal plasma loss mechanism is collisions with the interior struts used to support the dipole magnet. Once these supports have been removed and the magnet is truly levitating, we expect the effects of cross-field transport to be the primary determinant of the density profile. We have also observed how the profile is affected both by changes in ECR heating and neutral gas fuelling. In particular, gas fuelling experiments allow us to compare density profile changes with measurments of low frequency modes. Lastly, we document some of the technical improvements now planned to make the diagnostic’s function more stable and our analysis more reliable.
Characterization: A2,E1
Comments:
Please group with LDX posters (Garnier et al., Kesner et al., Ellsworth et al.)
