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Experimental characterization of drift-interchange instabilities in a simple toroidal plasma
Ist Teil von
Physics of plasmas, 2006-10, Vol.13 (10), p.102104-102104-9
Ort / Verlag
United States: American Institute of Physics
Erscheinungsjahr
2006
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Low frequency electrostatic instabilities are investigated on TORPEX [Fasoli, Labit, McGrath, Müller, Podestà, and Poli, Bull. Am. Phys. Soc.
48, 119 (2003)], a toroidal device for basic plasma physics experiments with a toroidal magnetic field
100
mT
and a small vertical magnetic field
(
⩽
4
mT
)
. A two-dimensional (2D) profile of the frequency and amplitude of density and potential fluctuations is reconstructed using electrostatic probes with high space and time resolution. The measured phase velocity, corrected for the Doppler shift induced by the
E
×
B
drift, is consistent with the electron diamagnetic drift velocity. The local dispersion relation, measured along and across the magnetic field, is in agreement with the predictions of a linear kinetic slab model for drift waves. Unstable modes are generated in regions of unfavorable curvature, where the pressure gradient is colinear with the magnetic field gradient. It is demonstrated that the curvature of the magnetic field lines is essential for driving the observed instabilities, which are therefore identified as drift-interchange modes.