Development Of EAST Polarimeter Interferometer System

Both electron density and current density are fundamental elements in tokamak plasma.When we research tokamak operational mode we found that plasma current involved in the process of Magneto-Hydro-Dynamic(MHD)equilibrium.Plasma internal transport barrier will be established when using off-axis current drive to achieve hollow current profile,which will significantly improve core area constrains.Some research suggests that the change of current density profile will lead to magnetic shear change,influence the plasma transport,and make its by the anomalous transport down to the level of the new classical transport,which prompted the establishment of the internal transport base.Because of the plasma current density distribution is closely related to the stability of magnetic liquid,so in tokamak and fusion reactor,MHD events plays an extremely important role in the feedback control.With years of development,polarimeter-interformeter is identified as one of the most reliable electron density and current profile measurements method.In order to adapt to EAST discharge,the observation and behavior research of current density under the condition of different discharge configuration and wall condition,different heating power,long pulse operation and optimize the current density diagnostic,we must to upgrade the current density diagnostic system.In the paper,the main works are develop 11-channel POLarimeter-INTerferometer(POINT)system and improve the spatial resolution of POINT system and measurement precision of the current distribution.We have completed the optimization of optical and mechanical design,analyzed and solved the various reducing error,improved measurement accuracy of POINT system,perfected the calibration method and calibration precision of the system,completed the standing wave error theory analysis and experiment.Current distribution and the electron density distribution and electronic density perturbations ware accurate measured and analyzed by using the POINT system.In the thesis,diagnostic principle of polarimeter-interformeter is briefly reviewed firstly.Several measurement methods of polarimeter-interformeter are introduced and contrasted,we finally decide to adopt three wave technique.Based on the gaussian beam propagation principle and the analysis of the infrared optical element,the optical design of POINT system is given,including optical path design,optical simulation,Optical element size design and so on.The optical table and optical tower design is described,and the mechanical vibration of POINT system is tested,finally,we can be sure that the error caused by mechanical vibration is less than the measurementprecision.In order to improve the measurement accuracy and assure the authenticity and reliability of measurement data,we need to analyze and compute the systematic error in detail,and give the corresponding processing method.Base on the Faraday Angle data,we analyze the stray lights effect on the influence of Faraday rotation measurement for POINT system on EAST.An optical isolator is designed to eliminate the stray light in optical system,which will improve the measurement accuracy.The electron density and current density profile can be measured accurately due to collinear adjustment,the polarization adjustment,Stray light elimination and so on.Finally,the temporal resolution reach?1?s,the accuracy of lineintegrated electron density can reach?1×1016m-2,the measuring accuracy of Faraday rotation angle could reach?0.1.Finally the experimental operation of the system is described,the data of electron density and Faraday rotation Angle with high temporal,spatial resolution are obtained,and combining the Digital phase demodulator(DPD)system,the electron density data can be used for plasma density feedback control,and lay a foundation for the current density profile and vertical displacement feedback control.