基于最小二乘法的EAST托卡马克光学等离子体边缘重建（英文）

Optical plasma boundary reconstruction based on least squares for EAST Tokamak

重建等离子体位形是托卡马克装置中一个非常重要的课题。平衡与反演编码(equilibrium and fitting,EFIT)是部分托卡马克中常用的等离子体边缘重建方法。然而,这种磁方法有一些不可避免的缺点。提出一种光学等离子体边缘重建算法,将EFIT编码结果作为标准值学习光学重建模型。在边缘提取方面,传统边缘检测方法不能提取较清晰的等离子体边缘。因此,提出一种基于全局对比度的方法在图像平面提取等离子体边缘。这种方法对光照有很好的鲁棒性。用一个同阶多项式和一个转换矩阵拟合提取等离子体边缘和EFIT重建等离子体边缘。为在没有相机标定的前提下获取转换矩阵,用最小二乘法最小化光学边缘和EFIT重建边缘误差,得到一个数学模型,该数学模型将提取的等离子体边缘从一个图像平面转换到托卡马克极向平面。一旦获得这个转换矩阵,便可在捕获的任意图像重建光学等离子体边缘。展示了所提方法和EFIT之间的误差,并讨论不同多项式阶数的实验结果。

Reconstructing the shape and position of plasma is an important issue in Tokamaks. Equilibrium and fitting（EFIT） code is generally used for plasma boundary reconstruction in some Tokamaks. However, this magnetic method still has some inevitable disadvantages. In this paper, we present an optical plasma boundary reconstruction algorithm. This method uses EFIT reconstruction results as the standard to create the optimally optical reconstruction. Traditional edge detection methods cannot extract a clear plasma boundary for reconstruction. Based on global contrast, we propose an edge detection algorithm to extract the plasma boundary in the image plane. Illumination in this method is robust. The extracted boundary and the boundary reconstructed by EFIT are fitted by same-order polynomials and the transformation matrix exists. To acquire this matrix without camera calibration, the extracted plasma boundary is transformed from the image plane to the Tokamak poloidal plane by a mathematical model,which is optimally resolved by using least squares to minimize the error between the optically reconstructed result and the EFIT result. Once the transform matrix is acquired, we can optically reconstruct the plasma boundary with only an arbitrary image captured. The error between the method and EFIT is presented and the experimental results of different polynomial orders are discussed.