No abstract

We report the experimental results on the turbulence energy transfer in a cylindrical laboratory plasma based on the data obtained by a set of quadruple Langmuir probe on Zheda plasma experiment device. The turbulence energy transfer is directly embodied in the alternating change in the fluctuation amplitudes between the low frequency turbulence at ∼0.1–0.2 kHz and the drift wave (DW) turbulence at ∼1–2 kHz. The estimation of the radial electric field and the bispectral analysis of the experiments suggest that the DW turbulence gains the energy from the low frequency turbulence with the magnetic field increase. The energy transport due to the interaction between the low frequency turbulence and the DW turbulence is a possible reason to drive the turbulence energy transfer associated with the magnetic field increase in the laboratory plasma.

An intrinsic evolution in the decoupling–coupling–decoupling (DCD) of the electron density and temperature responding to the magnetic field change is observed in a cylindrical laboratory plasma device. Experimental results show that the density and the temperature decouple in the low magnetic field, couple with higher magnetic field, and decouple again with a continuous magnetic field increase. An element physical picture of the DCD regime is unraveled based on the analyses of gradient lengths, the turbulence propagation directions, the turbulence spatial scales, and the relationship between the normalized collision rates and the poloidal mode numbers.