1. Alfven Oscillations in the TUMAN-3M Tokamak Ohmic Regime
The bursts of high frequency oscillations (~1МHz) identified as Alfven waves were registered by magnetic probes in OH discharges at ne <1.5·1019m-3
Typically the Alfven oscillations bursts correlate with the moments of the sawtooth crash when fast density fall happens
Sawtooth crushes may cause fast change in magnetic field geometry and its magnitude resulting in strong Et generation which at low density can generate runaway electrons exciting the Alfven waves
Spectrum of MHD activity in OH plasma in comparison with central ne(t) evolution
Ip~150 kA, Bt~ T
Frequency of the HF oscillation follows the dependence of Alfven wave velocity VA on magnetic field strength and plasma density:
VA=Bt/(4πmini)0.5
Frequency of the oscillations was f≈VA/2πR, i.e. the ratio λ/2πR≈1 which corresponds to the Alfven eigenmode with toroidal mode number n=1
Frequency of HF oscillations as a function of Bt/ne0.5