Slide-away discharges are achieved by decreasing the plasma density or ramping down the plasma current in runaway discharges in the HT-7 tokamak. In the case of plasma current ramp down, the ratio of the electron plas...Slide-away discharges are achieved by decreasing the plasma density or ramping down the plasma current in runaway discharges in the HT-7 tokamak. In the case of plasma current ramp down, the ratio of the electron plasma frequency to the electron cyclotron frequency is higher than in the stationary pulses when the discharge goes into a slide-away regime. The instability regime is characterized by relaxations in the electron cyclotron emission due to relativistic anomalous Doppler effect which transfers energy from parallel to perpendicular motion. The triggering of relativistic anomalous Doppler effect at higher density by ramping down of plasma current may provide a alternative runaway energy control scenario.展开更多
Spatio-temporal evolutions of the sawteeth activities are measured simultaneously with a 16 channel high spatio-temporal resolution electron cyclotron emission （ECE） heterodyne radiometer on HT-7 and the evolutions ...Spatio-temporal evolutions of the sawteeth activities are measured simultaneously with a 16 channel high spatio-temporal resolution electron cyclotron emission （ECE） heterodyne radiometer on HT-7 and the evolutions of the sawteeth are found to be diffusive in character. By a perturbative analysis, the electron heat diffusivity Хe inferred by time-to-peak method and Fourier transform shows a good agreement. The value of electron heat diffusivity shows radial asymmetry between the low magnetic field side （LFS） and the high magnetic field side （HFS）. It is observed that with the increase in plasma density, the electron heat diffusivity decreases and the confinement of energy is improved. By comparing with Хe^pb inferred by static power balance analysis, the result indicate that Хe^hp is larger than Хe^pb by a factor ranging from 2 to 10.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 10675124, and the Natural Science Foundation of Yunnan Province. The authors thank the HT-7 group for assistance.
文摘Slide-away discharges are achieved by decreasing the plasma density or ramping down the plasma current in runaway discharges in the HT-7 tokamak. In the case of plasma current ramp down, the ratio of the electron plasma frequency to the electron cyclotron frequency is higher than in the stationary pulses when the discharge goes into a slide-away regime. The instability regime is characterized by relaxations in the electron cyclotron emission due to relativistic anomalous Doppler effect which transfers energy from parallel to perpendicular motion. The triggering of relativistic anomalous Doppler effect at higher density by ramping down of plasma current may provide a alternative runaway energy control scenario.
基金National Natural Science Foundation of China(No.10335060)the Core University Program between China and Japan
文摘Spatio-temporal evolutions of the sawteeth activities are measured simultaneously with a 16 channel high spatio-temporal resolution electron cyclotron emission （ECE） heterodyne radiometer on HT-7 and the evolutions of the sawteeth are found to be diffusive in character. By a perturbative analysis, the electron heat diffusivity Хe inferred by time-to-peak method and Fourier transform shows a good agreement. The value of electron heat diffusivity shows radial asymmetry between the low magnetic field side （LFS） and the high magnetic field side （HFS）. It is observed that with the increase in plasma density, the electron heat diffusivity decreases and the confinement of energy is improved. By comparing with Хe^pb inferred by static power balance analysis, the result indicate that Хe^hp is larger than Хe^pb by a factor ranging from 2 to 10.
