Electron Heat Diffusivity Measurement by Perturbative Method on HT-7 Tokamak

Abstract

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 χe 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 χpbe inferred by static power balance analysis, the result indicate that χhpe is larger than χpbe by a factor ranging from 2 to 10.