Observations of toroidicity-induced Alfven eigenmodes in a reversed field pinch plasma

• High frequency peaks in the spectra of magnetic field signals have been detected at the edge of Extrap-T2R [P. R. Brunsell, H. Bergshker, M. Cecconello, J. R. Drake, R. M. Gravestijn, A. Hedqvist, and J-A. Malmberg, Plasma Phys. Controlled Fusion, 43, 1457 (2001)]. The measured fluctuation is found to be mainly polarized along the toroidal direction, with high toroidal periodicity n and Alfvenic scaling (f proportional to B / root m(i)n(i)). Calculations for, a reversed field pinch plasma predict the existence of an edge resonant, high frequency, high-n number toroidicity-induced Alfven eigenmode with the,observed frequency scaling. In addition, gas puffing experiments show that edge density fluctuations are responsible for the rapid. changes of mode frequency. Finally a coupling with the electron drift turbulence is proposed as drive mechanism for the eigenmode.

Keyword

tokamaks

mode

excitation

turbulence

particles

transport

rotation

spectra

Publication and Content Type

ref (subject category)

art (subject category)