Equilibrium and stability studies of plasmas confined in a dipole magnetic field using magnetic measurements

The Levitated Dipole Experiment (LDX) is the first experiment of its kind to use a levitated current ring to confine a plasma in a dipole magnetic field. Unlike most other confinement devices, plasma compressibility stabilizes and allows the plasma to attain a peak beta on the order of unity. Various magnetic sensors have been designed, calibrated, installed, and operated to reconstruct the plasma pressure profile through least-squares fitting to model profiles. Although both isotropic and anisotropic models are used, the latter is critical in deducing the correct beta values for the electron cyclotron resonance heated (ECRH), anisotropic LDX plasmas. The simpler isotropic models give accurate spatially integrated quantities of the pressure profile. The reconstruction of LDX plasmas requires overcoming unique obstacles. Because the floating coil is superconducting, care must be taken when interpreting magnetic signals, which measure the sum of the plasma current and the decrease in the floating coil current. The coupling of these two quantities, in addition to the large physical distances between the sensors and the plasma, makes the magnetic measurements sensitive mostly to the plasma dipole moment. A family of current and pressure profiles with the same dipole moment can therefore fit the measurements equally well. The ambiguity in determining the pressure profile is resolved by supplementing the magnetics with X-ray emissivity data. Internal flux loops close to the plasma will be added in the future to resolve higher order moments.

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

2007

Author dc:creator

• Karim, Ishtak

Advisor dc:contributor.advisor

• Jay Kesner and Darren Garnier.

• 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/1721.1/41294
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/41294

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/41294