HL-2A装置电子密度多道干涉测量实验系统

电子密度是核聚变等离子体研究中的一个主要物理参数，为获取电子密度时空分布的准确信息，结合HL-2A装置结构特点设计并建立了八道FIR激光干涉仪测量系统。在长光路的布局中采用了介质波导传输，研制了长谐振腔高功率HCN波导激光器。另外为减少干扰影响在差拍信号数据采集电子学中采用了数字锁相滤波FPGA技术, 并用软件和硬件两种相位比较方法监测电子密度，实现了密度随时间变化的实时显示。在等离子体放电中干涉仪系统测量精度可达1/33条纹，相应密度约为1.3×10¹¹cm^-3，时间分辨为0.1ms。

Experimental system of measuring density profile with multi-channel interferometer on the HL-2A tokamak

To measure the electron density profile, a new system of the multi-channel FIR laser interferometer has been designed and set up on HL-2A tokamak (with divertor configuration). A series of dielectric wave-guides are employed in the arrangement of long distance optic path and a high power HCN laser with six-meter cavity has been developed, in addition, the lock-in loop filter with FPGA technology has been adopted to reduce the disturb effect. The phase-comparison methods of software and hardware are simultaneously used to monitor the electron density and to display the density evolution timely. The accuracy of the multi-channel interferometer is closed to 1/33 fringe, the corresponding density is 1.3×1011cm-3, and the time resolution is 0.1ms.