由于等离子体密度梯度和机械振动的存在,对于密度在1013~1016cm-3范围的等离子体,通常需要采用外差式干涉仪进行小相位检测。包括Z箍缩、等离子体枪等在内的脉冲等离子体持续时间通常在数十纳秒到1 ms,而机械振动等因素引起的相位移动的周期大于1 ms,根据这种现象,采取40 mW的He-Ne激光器,迈克尔逊式光路,外差式记录系统和相位跟踪的方法,建立了一种高灵敏度干涉仪。干涉仪的最高灵敏度约为0.5°,空间分辨和时间分辨分别为1.4 mm和250 ns,成功测量的最低等离子体密度为1014cm-2。该干涉仪结构简单而且可以获得连续的时间分辨,能较广泛地用于持续时间较短的等离子体密度测量。 Because of the plasma density gradient and the mechanical vibration, the small phase detection of heterodyne interferometer is usually required for the plasma with density in the range of 1013 ~ 1016cm-3. Pulsed plasmas, including Z-pinch, plasma guns, and the like, typically last for tens of nanoseconds to 1 ms in duration, and periods of phase shift due to mechanical vibrations, etc., are greater than 1 ms. According to this phenomenon, a 40 mW He-Ne laser, Michelson optical path, heterodyne recording system and phase tracking method, a high sensitivity interferometer was established. The maximum sensitivity of the interferometer is about 0.5 °, the spatial resolution and time resolution are 1.4 mm and 250 ns, respectively, and the lowest plasma density successfully measured is 1014 cm -2. The interferometer is simple in structure and can obtain continuous time resolution, and can be widely used for plasma density measurement with short duration.