出于开关性能参数和结构要求考虑，PTS装置脉冲输出开关设计为3对自击穿电极间隙的水介质开关，间隙结构采用板-球间隙的同轴-三平板结构。选择水介质自击穿开关作为研究对象,进行了1.5 MV同轴结构开关研究，并在此基础上开展了4 MV同轴-三平板结构开关研究。开关实验达到的技术指标为：自击穿电压3.5 MV，导通电流500 kA，电感65 nH，自击穿时间分散性极差4.0 ns(1.3 ns均方根值)。

The self-breakdown water switch with coaxial-triplate configuration is used for the pulse output switch of the pulse forming section in Primary Test Stand (PTS). The research contains two stages, the first is the 1.5 MV coaxial water switch experiment on FLASH-Ⅱand the second is the experiment of 4 MV coaxial-triplate multi-channel water switch on the prototype module of PTS. Results show that the output current is 500 kA with 100 ns rise time at 3.5 MV self-breakdown voltage, the total switch inductance is 65 nH, and the jitter of charging time is 1.3 ns.