Submitted EFTSOMP2009- Workshop on Electric Fields, Turbulence and Self-Organisation in Magnetized
Plasmas, July 6-7, 2009, Sofia, Bulgaria
Measurements of high frequency magnetic activity in a reversed field pinch plasma
S. Spagnolo(1,2), M. Zuin(1), R. Cavazzana(1), E. Martines(1), M. Spolaore(1), N. Vianello(1)
(1) Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Corso Stati Uniti 4, 35127 Padova, Italy
(2) Dip. di Fisica “G.Galilei”, Università di Padova, via F. Marzolo 8, 35131 Padova, Italy
Coherent high frequency magnetic activity has been detected at the edge of the RFX-mod
reversed field pinch (RFP) experiment. The analysis is performed by means of a large set of
magnetic in-vessel coils and of an insertable edge probe, equipped with a matrix of magnetic
sensors. The measured fluctuations are found to be mainly polarized along the toroidal
direction, which at the edge of the RFP configuration is nearly perpendicular to the main
magnetic field. The activity rises as the reversal parameter F becomes deeper and seems to be
related to the spontaneous magnetic reconnection events, which characterize RFP plasmas.
Power spectra show a peak at about 50-100 kHz, at an almost given toroidal mode number, n.
Moreover a close relation between the toroidal mode number and the safety factor, q has been
observed: the measurements performed with the insertable probe show that n and q(r) are in
inverse proportion. The scaling of the measured spectra with different parameters has been
computed to investigate the possible Alfvénic nature of the measured fluctuations.