气体开关是脉冲功率系统的关键部件，开关的火花通道阻抗直接影响负载电压的陡度及其能量传输效率。提出一种光谱学诊断方法，通过对火花通道成像光谱的时空分辨测量，获得通道半径及电导率，从而计算时变的火花电阻。光谱测量结果表明,氮气间隙火花放电通道电子温度为2~3 eV，通道电导率先增大后减小，最大值约16 000 S，随着放电发展，火花通道电阻从绝缘状态快速跌落并趋于稳定值，时变趋势与电学计算结果基本吻合。3~100 kPa范围内，随着气压增大，放电通道半径减小，火花通道电阻增大。

The gas switch is one of the key components in pulsed power system and the impendence of spark channel greatly affects the efficiency of power delivery and the rising time of voltage applied to the load, but accurate measurement of spark resistance under oscillatory damped current pulse is difficult. In this paper, a spectrographic method is put forward. Through measuring the emission spectrum of spark channel with time and spatial resolution, the spark radius and conductivity are estimated and the spark resistance is calculated. The results show that electron temperature of nitrogen spark is about 2-3 eV while the conductivity of spark channel increases rapidly at first and then gradually decreases with a maximum of 16 000 S. As the spark channel develops, spark resistance drops rapidly from insulation and reaches a saturation value, and the time-dependent property of spark resistance fits well with the calculated results. In the pressure ranged from 3 to 100 kPa, the spark radius decreases and the spark resistance increases with the increase of pressure.