Forward modelling of the Cotton-Mouton effect polarimetry on EAST tokamak  

作　　者：沈敏勇 张际波 张耀 揭银先 刘海庆 谢锦林 丁卫星 Minyong SHEN;Jibo ZHANG;Yao ZHANG;Yinxian JIE;Haiqing LIU;Jinlin XIE;Weixing DING(School of Nuclear Science and Technology,University of Science and Technology of China,Hefei 230026,People's Republic of China;Institute of Plasma Physics,Chinese Academy of Sciences,Hefei 230031,People's Republic of China)

机构地区：[1]School of Nuclear Science and Technology,University of Science and Technology of China,Hefei 230026,People's Republic of China [2]Institute of Plasma Physics,Chinese Academy of Sciences,Hefei 230031,People's Republic of China

出　　处：《Plasma Science and Technology》2024年第3期100-117,共18页等离子体科学和技术（英文版）

基　　金：financially supported by National Natural Science Foundation of China(No.12127809)。

摘　　要：Measurement of plasma electron density by far-infrared laser polarimetry has become a routine and indispensable tool in magnetic confinement fusion research.This article presents the design of a Cotton-Mouton polarimeter interferometer,which provides a reliable density measurement without fringe jumps.Cotton-Mouton effect on Experimental Advanced Superconducting Tokamak(EAST)is studied by Stokes equation with three parameters(s_(1),s_(2),s_(3)).It demonstrates that under the condition of a small Cotton-Mouton effect,parameter s_(2)contains information about Cotton-Mouton effect which is proportional to the line-integrated density.For a typical EAST plasma,the magnitude of Cotton-Mouton effects is less than 2πfor laser wavelength of 432μm.Refractive effect due to density gradient is calculated to be negligible.Time modulation of Stokes parameters(s_(2),s_(3))provides heterodyne measurement.Due to the instabilities arising from laser oscillation and beam refraction in plasmas,it is necessary for the system to be insensitive to variations in the amplitude of the detection signal.Furthermore,it is shown that non-equal amplitude of X-mode and O-mode within a certain range only affects the DC offset of Stokes parameters(s_(2),s_(3))but does not greatly influence the phase measurements of Cotton-Mouton effects.

关 键 词：EAST Cotton-Mouton effect polarimeter interferometer electron density measurement Stokes vector 

分 类 号：TL631.24[核科学技术—核技术及应用]