Resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell reversed-field pinch
2002 (English)In: Physics of Plasmas, ISSN 1070-664X, Vol. 9, no 1, 212-221 p.Article in journal (Refereed) Published
Observations of resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell (tau (w)=6 ms) reversed field pinch are described. A nonresonant mode (m=1,n=-10) with the same handedness as the internal field grows nearly exponentially with an average growth time of about 2.6 ms (less than 1/2 of the shell time) consistent with linear stability theory. The externally nonresonant unstable modes (m=1,n >0), predicted by linear stability theory, are observed to have only low amplitudes (in the normal low-Theta operation mode of the device). The radial field of the dominant internally resonant tearing modes (m=1,n=-15 to n=-12) remain low due to spontaneous fast mode rotation, corresponding to angular phase velocities up to 280 krad/s. Phase aligned mode structures are observed to rotate toroidally with an average angular velocity of 40 krad/s, in the opposite direction of the plasma current. Toward the end of the discharge, the radial field of the internally resonant modes grows as the modes slow down and become wall-locked, in agreement with nonlinear computations. Fast rotation of the internally resonant modes has been observed only recently and is attributed to a change of the front-end system (vacuum vessel, shell, and TF coil) of the device.
Place, publisher, year, edition, pages
2002. Vol. 9, no 1, 212-221 p.
Fusion, Plasma and Space Physics
IdentifiersURN: urn:nbn:se:kth:diva-74854DOI: 10.1063/1.1426101ISI: 000172785900025ScopusID: 2-s2.0-0036149652OAI: oai:DiVA.org:kth-74854DiVA: diva2:490121
QC 201312032012-02-032012-02-032013-12-03Bibliographically approved