Mechanism for blob generation in the TORPEX toroidal plasma
- Centre de Recherche en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, Association EURATOM-Confederation Suisse, CH-1015 Lausanne (Switzerland)
- Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)
- Center for Energy Research, University of California, San Diego, La Jolla, California 92093 (United States)
The mechanism for blob generation is detailed in the toroidal magnetized plasma of the TORPEX device [Fasoli et al., Phys. Plasmas 13, 055902 (2006)] using an experimental configuration, which features a plasma region dominated by a coherent wave and a region on the low field side characterized by the propagation of blobs. Predictions from linearized 2D drift-reduced Braginskii equations are compared with experimental data, revealing the interchange nature of the coherent wave. The dynamics of blob formation is investigated using time-resolved measurements of two-dimensional profiles of electron density, temperature, plasma potential and ExB velocity. Blobs form from radially elongated structures associated with the interchange wave. When a blob is generated, the following sequence of events is observed: 1) A decrease of local pressure gradient length provides an increase of the interchange mode drive; 2) in response, the interchange mode increases in amplitude and expands in the radial direction forming a radially elongated structure from the wave crest; 3) the elongated structure is convected by the ExB flow and is eventually sheared off, forming a blob on the low field side. The dependence of the blob amplitude upon the minimum pressure radial scale length before the blob ejection is also investigated.
- OSTI ID:
- 21120347
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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