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Measurement and Control of Plasma Turbulence in PANTA

par Caroline CHAMPENOIS - publié le

séminaire du laboratoire
mardi 20 juin 14:00 service 361 campus Saint-Jérôme

S. Inagaki,

Research Institute for Applied Mechanics, Kyushu University

abstract :

Magnetically confined plasma is one of the typical non-equilibrium open systems and is characterized by strong spatiotemporal inhomogeneities. The spatial inhomogeneities (free energy) excite waves and instabilities. Then multi-scale fluctuations co-exist and interact each other, i.e. plasma becomes turbulent and the turbulence relaxes the spatial inhomogeneities through enhancement of transport. This mechanism forms thermo- dynamical structure where gradients, flows and turbulence co-exist. Structure formation has a broad interest in the non-equilibrium systems and widely recognized as key issues to be solved in the non-linear physics. For more comprehensive understanding of structure formation in plasma, measurement and control of plasma turbulence are essential. We experimentally investigated plasma turbulence by using a linear magnetic device, PANTA. Cylindrical argon plasma (radius of 6 cm and axial length of 4 m) is generated by 3-6 kW rf (7 MHz) power and radially confined by homogeneous axial magnetic field (0.06-0.15 T). Typical parameters measured by YAG-Thomson scattering and laser induced fluorescence are ne0 1.0x1019 m-3, Te0 3 eV and Ti0 0.3 eV. By means of Langmuir probe and Mach probe, the spatial structure of flows and turbulent fluctuation are measured. Low frequency (1-5 kHz) drift waves are excited in PANTA. Here we discus ; 1) how to observe three-wave coupling in turbulence and how to evaluate azimuthal and axial Reynolds stresses (which drive flow shear), 2) control of turbulence structure by end-plate biasing. Understanding of structure formation mechanism will contribute to further study on fusion plasma control.

contact : Alexandre Escarguel


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