Measurements Of Diamagnetism And Energy Confinement Time Scaling In HT-7 Superconducting Tokamak

The thesis consists of two parts. One is diamagnetic diagnostics of plasma, and the other is internal inductance in HT-7 tokamak. A pair of diamagnetic compensation loops installed in the poloidal plane inside the vacuum vessel in order to measure diamagnetism in HT-7 superconducting tokamak, the relative error of poloidal beta β_p is less than ±7% by means of software compensation. Synchronously,investigation of the energy confinement time in ohmic plasmas and Lower Hybrid Current Drive (LHCD) in HT-7 has been performed. The results of diamagnetic measurement in OH discharges in HT-7 indicate total energy confinement time Ï„_E varies linearly with the central line-averaged electron density up to n e<2.5×10¹³cm^-3. It saturates in the higher n e. It saturated at 22 ms. Comparison of the experimental values with Neo-Alcator scaling law shows the energy confinement time is in good agreement with the Neo-Alcator scaling law. In the LHCD plasmas, the experimental results show that the total energy is increased with the input LHW power, however the energy confinement time is degraded with increased total power, taking on typical L-mode characteristic. Owing to effect of the plasma current and the electron density in L-mode scaling law, experiments at different current and density have been performed. By considering contribution of the fast electron energy, the energy confinement times have been corrected, and the confinement time is in good agreement with the low confinement mode (L mode) scaling law of ITER89-P in high electron density and in high plasma current.