首次采用光学多道诊断系统，通过Ｈα线的观测，研究了托卡马克交流运行期间等离子体的时空行为。结果发现：在电流过零处，等离子体未完全熄灭，使得电流转换后不需要第二次击穿。等离子体的时空行为与电流波形有关。 For the first time, an optical multi-channel diagnostic system was used to analyze the plasma spatiotemporal behavior during tokamak AC operation by observing the Hα line. As a result, it was found that at the current zero crossing, the plasma did not completely extinguish so that the second breakdown was not required after current conversion. The space-time behavior of the plasma is related to the current waveform.