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Experiments on the Propagation of Plasma Filaments in VTF

Egedal, J (MIT)
Thursday 29 July 2010, 14:00-14:40

Seminar Room 2, Newton Institute Gatehouse


We investigate experimentally the motion and structure of isolated plasma filaments propagating through neutral gas. Plasma filaments, or "blobs," arise from turbulent fluctuations in a range of plasmas. Our experimental geometry is toroidally symmetric, and the blobs expand to a larger major radius under the influence of a vertical electric field. The electric field, which is caused by B and curvature drifts in a 1/R magnetic field, is limited by collisional damping on the neutral gas. The blob's electrostatic potential structure and the resulting EB flow field give rise to a vortex pair and a mushroom shape, which are consistent with nonlinear plasma simulations. We observe experimentally this characteristic mushroom shape. We also find that the blob propagation velocity is inversely proportional to the neutral density and decreases with time as the blob cools [1]. [1] Katz N, Egedal J, et al, (2008) Phys. Rev. Lett. 101, 015003.


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