Optical Tomography Diagnostics on an FRC Plasma
Abstract
Field Reversed Configuration (FRC) plasmas are too hot and too dense for probes to survive inside. This means that it is necessary to use non-invasive techniques to determine the plasma's properties. We have developed a diagnostic for using visible light radiation to determine the shape and position of an FRC plasma. Visible light does not require the expensive detectors or lasers of other diagnostic techniques, but should still allow us to generate a picture of the outside edge of the plasma. This data should be especially interesting when the FRC plasma spins as it undergoes instability. Two optical fan arrays are installed inside the current experimental setup, 90 degrees out of phase, at the edge of the quartz tube. By using a ball lens and optical fibers it is possible to get line averaged values for the visible light at a range of angles. The data obtained can then be analyzed; inversion techniques and singular-value decompositions (SVD) can be used to generate a map of the plasma. The most intense light comes from line radiation from the edge of the plasma, while density data from the interferometer is chord-averaged from the center. By combining the two techniques one gets a more complete picture of the overall plasma profile. This will also be useful when analyzing radiation data from a bolometer. These inversion techniques could also be used for other future experiments, for example, a pinhole x-ray diagnostic.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPGP1040B