Fang Dongfan, Sun Qizhi, Zhao Xiaoming, Jia Yuesong
Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, P. O. Box 919-108, Mianyang, Sichuan 621999, People's Republic of China.
Rev Sci Instrum. 2014 May;85(5):053510. doi: 10.1063/1.4875584.
A 633 nm laser interferometer has been designed based on a novel concept, which, without the acousto-optic modulator or the demodulator circuit, adopts the fibers to connect all elements except photodetectors and oscilloscope in this system to make it more compact, portable, and efficient. The noteworthy feature is to mathematically compare the two divided interference signals, which have the same phase-shift caused by the electron density but possess the different initial phase and low angular frequencies. It is possible to read the plasma density directly on the oscilloscope by our original mathematic demodulation method without a camera. Based on the Abel inversion algorithm, the radial electron density profiles versus time can be obtained by using the multi-chord system. The designed measurable phase shift ranges from 0 to 2π rad corresponding to the maximum line integral of electron density less than 3.5 × 10(17) cm(-2), and the phase accuracy is about 0.017 rad corresponding to the line integral of electron density accuracy of 1 × 10(15) cm(-2). After the construction of eight-chord interferometer, it will provide the detailed time resolved information of the spatial distribution of the electron density in the field-reversed configuration (FRC) plasma target produced by the "Yingguang-1" programmed-discharge device, which is being constructed in the Key Laboratory of Pulsed Power, China Academy of Engineering Physics.
基于一种新颖的概念设计了一台633纳米激光干涉仪，该干涉仪在本系统中无需声光调制器或解调器电路，采用光纤连接除光电探测器和示波器之外的所有元件，从而使其更紧凑、便携且高效。值得注意的特点是对两个分开的干涉信号进行数学比较，这两个信号由电子密度引起的相移相同，但具有不同的初始相位和低角频率。通过我们原始的数学解调方法，无需相机即可直接在示波器上读取等离子体密度。基于阿贝尔反演算法，利用多弦系统可获得径向电子密度分布随时间的变化情况。所设计的可测量相移范围为0至2π弧度，对应电子密度的最大线积分小于3.5×10(17)厘米(-2)，相位精度约为0.017弧度，对应电子密度线积分精度为1×10(15)厘米(-2)。八弦干涉仪建成后，将提供由中国工程物理研究院脉冲功率重点实验室正在建造的“荧光一号”程控放电装置产生的场反向配置（FRC）等离子体靶中电子密度空间分布的详细时间分辨信息。
