The linear and the non-linear behaviors of the ion temperature gradient (ITG) mode in a plasma with regularized κ-distributed electrons are investigated using the fluid model. The dispersion relation of the ITG mode obtained on the basis of the local approximation shows that the growth rate of the ITG mode decreases with the increase in the spectral index κ and the exponential cut-off parameter α. It indicates that the presence of the superthermal electron leads to destabilization of the ITG mode, especially in the low κ ( κ < 1.5) region. In addition, the existence and the nature of the soliton structure driven by the ITG are studied using the pseudopotential technology. The soliton amplitude increases with the increase in the exponential cut-off parameter α and the spectral index κ, whereas the width of the soliton varies inversely. The present results will help to understand the low-frequency electrostatic wave and nonlinear structure in space and experimental plasmas with non-thermal electrons.
Under the framework of the two-timescale method, we derived the two-temperature-electron Zakharov equations which can describe the wave-wave interaction among Langmuir wave, electromagnetic wave, and electron acoustic waves. Numerical results reveal that the modulation instability will lead the wave field collapse into a turbulent state. The spectrum obtained from the Fourier analysis shows a cascade of energy from large to small scales. In the collapse processes, the hot electrons are expelled by the ponderomotive force induced by the high frequency waves, and then density cavitons are formed.
The NanChang Spherical Tokamak (NCST), a new compact (plasma major radius R = 0.40 m, minor radius a = 0.24 m, and aspect ratio A = 1.67) spherical tokamak, is suitable for teaching and scientific research activities at the university. The principal goal of the device is to initiate plasma currents by utilizing merging compression. At present, the NCST has a total of five complete coil systems, including the coils and their dedicated power supplies, to generate and control the plasma as per the experimental objectives. This paper presents the NCST device and its coils, the design of the power supplies, and the simulation results of plasma configurations as well as the comparison of experimental and simulation results of the above-mentioned power supply system.
The NanChang Spherical Tokamak (NCST) is a new compact tokamak (with an aspect ratio of R/a = 1.67) for exploring the merging compression by which the plasma start-up is highly efficient. In this paper, a magnetic diagnostic system is designed, calibrated, and constructed on the NCST to meet the requirements of measurements. Based on detailed testing and analysis, the reliability of the sensors is guaranteed by optimizing the support structure and installation process. In addition, high-precision positioning equipment is utilized to ensure the installation accuracy of the sensors. During the start-up phase of the NCST, plasma currents on the order of a few kiloamperes were measured despite that the commensurate signal of eddy current is also found in the conducting structure. The magnetic diagnostic system is now completely operational and meets the requirements of the physical analysis on the NCST.
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