由于等离子体密度梯度和机械振动的存在,对于密度在1013～1016 cm-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1014 cm-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。

A time-resolved sensitive interferometer without complex active stabilization was established, which has wide applicable perspectives for density measurements of pulsed plasma. Based on the distinct periods of the stochastic phase shift introduced by mechanical vibration (～ms) and of the phase shift introduced by plasma of density (～10 μs), a 40-mW He-Ne laser and a differential recording system were adopted in the interferometer with Michelson scheme and a phase tracking system. Sensitivity about 0.5° was reached and the corresponding minimum line-integral plasma density as low as 1014 cm-2 was measured. The spatial and temporal resolutions are 1.4 mm and 250 ns, respectively. The investigative background, general design consideration, systematic structure and procedure of data treatment of the interferometer were presented.