A 16-channel electron cyclotron emission (ECE) radiometer has been employed to observe the (m,n)=(2,1) magnetic island structure on HT-7 tokamak,where m and n represent the poloidal and toroidal mode number respectively.The results indicate that the island width is about 7 cm when the magnetic island is saturated during the m/n=2/1 mode.The location of resonance surface can be determined by plotting the contour of ECE relative fluctuation.This method could be applied to the HT-7 and EAST campaigns in the future for the research of neoclassical tearing modes (NTMs).
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