Progress of motional Stark effect polarimeter in HL-2A tokamak

doi:10.16568/j.0254-6086.201602002

Abstract

Abstract:

Two types of motional Stark effect (MSE) polarimeters were detected and the pilot experiments of measuring the magnetic pitch angle are carried out in the HL-2A tokamak. The main part of the first type consists of 4 polarizers and a spectrometer, and the accuracy of ±0.15° can be obtained. The pitch angles of magnetic field are achieved by 7 spatial channels covering 24 cm major radius with time resolution of 40 ms. The profiles of safety factor are obtained by combining with the equilibrium and reconstruction fitting code (EFIT). The position of q=1 surface is well consistent with the results measured by soft-X array. The other one based on a dual photo-elastic modulator (PEM) can obtain the accuracy of ±0.15° in the calibration experiments. The deviation angle between analyzing polarizer axis and the angular bisector of the dual PEM influences heavily on the linearity and the accuracy of the system. Time resolution of 20 ms was obtained for one channel during the pilot experiments.

Key words: Motional Stark effect, Polarized light, Safety factor

摘要：

在HL-2A 装置上发展了两类动态斯塔克效应(MSE)偏振仪并应用于磁场倾斜角的测量。其中被称为比值法的MSE 系统误差可以被控制在±0.15°以内。在HL-2A 装置实验中，利用该方法成功获得7 个空间点、径向覆盖范围为24cm 的磁场倾斜角剖面分布，其时间分辨可达到40ms。应用平衡重建代码(EFIT)结合MSE 测量数据的限定，可以得到安全因子(q)的径向分布，其中q=1 面的位置与软X 射线测量得到锯齿振荡反转面的位置一致。调制法MSE 在标定实验中误差也可控制在±0.15°以内。实验结果表明偏振片透振方向与双光学弹性调制器 (dual PEM)快轴夹角平分线的偏差对系统的线性和误差均有较大的影响。目前，该系统已经建成一个空间通道，测得磁场倾斜角的时间分辨可以达到20ms。

关键词: 动态斯塔克效应, 偏振光, 安全因子

CLC Number:

O536

CHEN Wen-jin1, HE Xiao-xue1, LIU Liang1, WEI Yan-ling1, MA Qian2, YU De-liang1. Progress of motional Stark effect polarimeter in HL-2A tokamak[J]. NUCLEAR FUSION AND PLASMA PHYSICS, 2016, 36(2): 104-110.

陈文锦1，何小雪1，刘亮1，魏彦玲1，马倩2，余德良1. HL-2A 装置上动态斯塔克效应偏振仪研究[J]. 核聚变与等离子体物理, 2016, 36(2): 104-110.

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