Studies of turbulence and wave coupling based on self organization process at SK/CG-1 machine

In the SK/CG-1 Machine, using the He gas pressures between 30 and 50 mTorr, a complex turbulence regime has been determined. During the on-set phase of 0.35 μs, besides the anomalous plasma resistivity, the ion acoustic instability is also observed. At the C-gun the plasma belt which contains the hot electrons at the energy range of 60-80 eV, breaks from the gun electrodes, the translation into plasmoid case occurs and then high electric fields about 5 kV/cm in the poloidal frame of the gun are produced. Thus, the electron-ion two stream instability and just after 0.1 μs, the ion acoustic instability is started. On the other hand, in the second phase, the beam plasma instability and the ion acoustic instability are parallelly sustained. The beam plasma instability includes also the W3 ion cyclotron instability. In addition, due to the toroidal magnetic field of poloidal frame and the electric field perpendicular to it, the density and temperature gradients come into existence. Probably at the end of the resonance of the drift wave and the ion acoustic wave, the drift wave turbulence commences. The time constant of the octagonal flux conserver is about 28-30 ms. After the turbulence, the electric field on the poloidal frame drops down to 900 V/cm and it is kept for 300 ms (E/e). Thus a wave coupling mechanism depending on the self organization process is sustained. Nevertheless, it has not yet been understood exactly if the propagation at the flux conserver is realized due to the reflections or the helicity transfer from the wave to the plasma. The frequency of the closed wave packet changes in the range of 25-5 kHz depending on the electron temperatures in the range of 30-5 eV. The average electron density is about 1014cm-3 and the global energy confinement times are found in the range of 65-250 μs. (author). 7 refs, 6 figs