Optical Testing And Construction Of EAST Microwave Imaging Reflectometry System

This dissertation breifly introduces the working principle and composition of the microwave imaging reflectometry(MIR)of Experimental Advanced Superconducting Tokamak.The main content includes the optical performance evaluation of the front-end optics,the Doppler effect experimental study of the MIR system,and the construction and debugging on the EAST.The first part is to study the optical performance of the MIR system through experimental testing and CodeV simulation.Setting up the entire MIR system in a laboratory environment,using a metal plane with a width of 1 cm as the reflection surface to translate from top to bottom in units of 5 mm.Analyze the signal strength collected by the receiving antenna at each position to give its polar detection position and spot radius on the reflection surface.The experimental results are consistent with the results given by the CodeV,which verifies that the processing of the optical lens of the receiving optical path meets the parameters designed by CodeV.The second part is the countertop experimental research on the Doppler effect of the MIR system.In the laboratory Setting up the entire MIR system,the surface of the metal round wheel with adjustable speed was used as the reflective surface.We measured the Doppler frequency shift observed by different receiving antennas at different speeds of the cutoff layer,and processed the experimental data by various methods.Found the best existing processing method:using double Gaussian function to fit the asymmetric part of the frequency spectrum to obtain the frequency shift value.The experimental frequency shift results are compared with the theoretical Doppler frequency shifts given by CodeV,and it is concluded that the edge lanes are well matched and the center lanes are very different.Our conjecture was that due to the limited size of the light spot detected by the antenna on the wheel reflection surface,the experimental and theoretical results of different antennas are different,and the conjecture is verified by further design experiments.The third part is to introduce the work content and construction process of the MIR system to the EAST device,including the construction of the MIR system optical platform,the design of the optical path and the determination of the optical axis,the construction of the back-end electronics system and the acquisition card system and Set the remote control of the system.By affixing a plane mirror on the window flange as a reflection,the overall debugging of the MIR system was performed,and the reflected signal collected and processed by the MIR system was successfully displayed on the oscilloscope.During the debugging process,it was found that the Schottky diode on the detection unit of the receiving antenna was not working properly.The damaged antenna array was detected and the diode was replaced,so that the 12 detection units of the receiving antenna can work normally and complete the MIR system.