Table Benchmark Of EAST Microwave Imaging Reflectometry System

Microwave Imaging Reflectometry(MIR)is a novel diagnostics technique to measure two-dimensional electron density flucturation on small section of Tokamak by combining reflectometry and large aperture optics together.In order to understand the working principle of all sub-systems of EAST MIR system throughly and to have fully understanding of performance of EAST MIR system along with any possible problems before officially employ EAST MIR system,tests and benchmarks are performed on EAST MIR system in laboratry setup.The table benchmark tests of EAST MIR system mainly contain two parts.The first part of tests is using CodeV to simulate performance of front-end optics system.According to the feature of MIR system,the front-end optics should have abilities to adjust radial focus position,polodial observation region and field curvature.And CodeV is used as gaussian optics simulator of front-end optics,the results of simulation shows that the imaging properties of front-end optics fufills requirements of EAST MIR system.And the influence of pitch and off-axis deviation of lens installation on imaging is also simulated by CodeV,results of which shows that off-axis deviation tends to have stronger impact of imaging than pitch deviation.Therefore,special attention on off-axis deviation is need during process of installation of front-end optics.Second part of table benchmark tests of EAST MIR system mainly focused on performance of hardwares of EAST MIR system along with validation of phase reconstruction and imaging properties adjustment of front-end optics.Because MIR system significantly relys on the measurement of phase of reflected signal to reconstruct the flucturation on specified cutoff layer,so the precision of phase measurement of reflected signal is vital to EAST MIR system.Since the phase is calculated from IQ signal out-putted by electronic modules of EAST MIR system,and any imbalance of IQ signal will introduce error to phase calculation.Therefore,the quality of IQ signal has direct impact on phase reconstruction.So,IQ signal quality needs to be assessed,and the assessment results shows that the quality of IQ signals meets the requirements.Therefore,to benchmark the performance of entire system,we use a periodic sinusiod corrugated wheel to simulated cutoff layer and set up entire system in laboratry.The results of benchmark verified the ability of phase reconstruction of electronic system and capability of imaging properties adjustment of front-end optics.